nonlinear simulations of jupiter s 5 micron hot spots large scale nonlinear simulations of jupiter s 5 micron hot spots produce long lived coherent structures that cause subsidence in local regions explaining the low cloudiness and the dryness measured by the galileo probe inside a hot spot like observed hot spots the simulated coherent structures are equatorially confined have periodic spacing propagate west relative to the flow are generally confined to one hemisphere and have an anticyclonic gyre on their equatorward side the southern edge of the simulated hot spots develops vertical shear of up to 70 meters per second in the eastward wind which can explain the results of the galileo probe doppler wind experiment

constraints on the core mantle boundary topography from p4kp pcp differential travel times 1 p4kp pcp differential travel times are examined to infer the core mantle boundary cmb topography a total of 362 p4kp pcp times are measured with a measurement error of 0 5 s the travel times are corrected for the earth s hydrostatic ellipticity and mantle heterogeneity using a p wave tomographic model spherical harmonic expansion up to degree 4 is adopted for model parameterization the p wave velocity heterogeneity is then estimated in the lowermost 150 km of the mantle to overcome the problem of underestimation of the velocity perturbation at the base of the mantle in the global 3 d p wave mantle model subsequently the cmb topography is inferred using the residues of the above processes since the odd degree components of the cmb topography are insensitive to the p4kp pcp times only the components of degrees 2 and 4 are solved for the resultant features indicate that the maximum amplitude of the cmb topography does not exceed 2 km with an uncertainty of less than 0 5 km a numerical test confirms that the pattern of degree 4 is more reliable with less amplitude recovery the obtained degree 4 pattern shows an amplitude of less than 1 km and indicates the presence of depressions under the circum pacific the central pacific and south africa

interpretation of the minch linear magnetic anomaly and of a similar feature on the shelf north of lewis by non linear optimization the linear negative magnetic anomaly which stretches continuously for 110 km across the north minch extending slightly west of north from loch ewe is interpreted in terms of an unusually wide dyke which does not reach the surface fourteen profiles taken from the aeromagnetic map have been interpreted using non linear optimization giving an excellent fit to a dyke having an average and fairly constant width of c 1 1km the depth to the upper surface of the interpreted dyke varies between 0 3 km and over 2 km it is reversely magnetized in a direction consistent with a tertiary or possibly earlier origin the average magnetization is estimated to be 0 51 am 1 a similar magnetic feature on the shelf to the north west of the butt of lewis is also interpreted in terms of a reversely magnetized dyke having a poorly resolved width of about 0 8 km a depth of about 0 7 km and a magnetization of 1 6am 1 on seismic evidence the minch dyke appears to be post jurassic in age and an early tertiary age seems most likely for both dykes it is suggested that they may be related either to the postulated large igneous pile of early tertiary age which forms the wyville thomson ridge or to the skye centre they appear to represent early tertiary extension of the crust which is taken up by more numerous narrow dykes further south

the topographic torque on a bounding surface of a rotating gravitating fluid and the excitation by core motions of decadal fluctuations in the earth s rotation general expressions with potential applications in several areas of geophysical fluid dynamics are derived for all three components of the contribution made by the geostrophic part of the pressure field associated with flow in a rotating gravitating fluid to the topographic torque exerted by the fluid on a rigid impermeable bounding surface of any shape when applied to the earth s liquid metallic core which is bounded by nearly spherical surfaces and can be divided into two main regions the torosphere and polosphere the expressions reduce to formulae given previously by the author thereby providing further support for his work and that of others on the role of topographic coupling at the core mantle boundary in the excitation by core motions of earth rotation fluctuations on decadal time scales they also show that recent criticisms of that work are vitiated by mathematical and physical errors contrary to these criticisms the author s scheme for exploiting earth rotation and other geophysical data either real or simulated in computer models in quantitative studies of the topography of the core mantle boundary cmb by intercomparing various models of a motions in the core based on geomagnetic secular variation data and b cmb topography based on seismological and gravity data has a sound theoretical basis the practical scope of the scheme is of course limited by the accuracy of real data but this is a matter for investigation not a priori assessment

core mantle boundary shape constraints inferred from the pressure torque acting between the core and the mantle summary in the last few years models of the flow at the top of the earth s core and of the related pressure field have been calculated from the secular variation of the geomagnetic field and core mantle topographies have been computed by seismologists a pressure torque results from the action of the pressure field on the core topography which can theoretically be computed from models of both the pressure field and the core mantle interface small scale features of the flow and of the topography are shown to be capable of contributing strongly to the pressure torque it is thus impossible to calculate the exact value of the torque from the knowledge of only the long wavelength components of the models but the interaction between the large scale components generates by itself torques two orders of magnitude larger than the torques inferred from the irregularities of the length of the day it is nevertheless possible to reconcile the topographic coupling mechanism with the length of the day observations keeping the amplitude of the core topography proposed by seismologists if an orthogonality relation between the geometry of the fluid upwellings and downwellings at the top of the core and the topography is satisfied it is shown how to compute such a topography for a given flow and close to an original topography provided by seismic tomography some consequences of the so inferred link between the fluid flow at the top of the core and the core mantle boundary topography are discussed

spatial distribution of visible lightning on jupiter spacecraft observations have provided evidence for the existence of lightning on venus1 3 jupiter4 5 saturn6 7 and uranus8 little is known however about the global distribution of lightning on these planets because of the limited spatial resolution and areal coverage of these previous detections which have principally involved radio frequency measurements two long exposure images obtained by the voyager 1 spacecraft of a small area on the nightside of jupiter have provided the only previously studied imaging observations of lightning on another planet9 10 here we present an analysis of all suitable voyager images of jupiter and evaluate the horizontal spatial distribution of visible lightning over most of one hemisphere essentially all the detectable activity is confined to very narrow latitude bands at 13 5 n and 49 n the active regions at 49 n are the brightest most numerous and periodic in longitude activity at this latitude is long lived and is most likely associated with moist convective regions deep in jupiter s atmosphere the longitudinal periodicity of the lightning storms may represent the effects of a planetary scale atmospheric wave trapped at the depth of the moist convection11 12

planetary waves in jupiter s equatorial atmosphere abstract voyager infrared radio occultation and imaging measurements provide a variety of observational evidence and constraints for planetary scale waves latitudinally trapped within jupiter s equatorial jet the visually prominent plumes encircling the planet at 8 deg north latitude show a longitudinal organization of wavenumber n 11 13 an apparently solitary plume also appears at about 8 deg south along the with other smaller periodic cloud features deviations in cloud tracked driff speed including differences in mean values to the north and south of the equator in excess of 25 m sec 1 may be crudely indicative of the magnitude of the associated wave phase speeds radio occultation retrievals of the temperature profiles at two equatorial longitudes show harmonic variation consistent with the stratospheric propagation of two components with vertical wavelengths of approximately 3 and 0 5 scale heights these observations may be consistently interpreted in terms of specific classes of equatorially trapped wave modes the gravest equatorial rossby mode with an equivalent depth of h 2 4 km with a stratospheric wavelength of 3 4 scale heights represents the most consistent interpretation of the plumes the inferred vetical eigenmode could be ducted by a deep statically stable layer possibly imposed by a roughly solar abundant water cloud depending upon the actual details of the moist convection an estimate of the relative growth rates for the near neutral forcing of rossby modes of the inferred equivalent depth implies a maximum for zonal wavenumber 11 the solitary plume feature to the south of the equator may be interpreted as a wavenumber 1 rossby mode with the same vertical scale possibly forced by the interaction between the equatorial jet and the great red spot smaller visual features may correspond to inertia gravity modes with vertical wavelengths comparable to the small harmonic of the occultation profiles galileo orbiter and probe observations will provide an essential test of the wave analysis and substantially enhance its diagnostic utility

aspherical structure of the core mantle boundary from pkp travel times maps of aspherical structure in the vicinity of the core mantle boundary have been constructed from a tomographic analysis of p df and p ab travel times in the distance range 150 180 these maps reveal long wavelength features not previously detected by mantle tomography the peak to peak amplitude of these features is on the order of 1 s in vertical travel time too large to be explained by conventional thermal boundary layer models or dynamically supported topography on the core mantle boundary we hypothesize the existence of one or more chemical boundary layers whose large scale accumulations on the surface of the core may in some ways be analogous to continents at the earth s surface

saturn s atmosphere at 1 10 kilometer resolution we present images of saturn from the final phases of the cassini mission including images with 0 5 km per pixel resolution as high as any saturn images ever taken notable features are puffy clouds resembling terrestrial cumulus shadows indicating cloud height dome and bowl shaped cloud structures indicating upwelling and downwelling in anticyclones and cyclones respectively and filaments which are thread like clouds that remain coherent over distances of 20 000 km from the coherence of the filaments we give upper bounds on the diffusivity and kinetic energy dissipation a radiative transfer analysis by sanz requena et al 2018 indicates that methane band imagery is most useful in determining cloud and haze properties in the 60 250 mbar pressure range our methane band imagery finds haze in this pressure range covering 64 74 planetocentric latitude filaments lie within the haze and cumulus clouds lie below it but pressure levels are uncertain below the 250 mbar level

multiparametric observation of volcanic lightning sakurajima volcano japan we recorded volcanic lightning generated by vulcanian explosions at sakurajima volcano using a synchronized multiparametric array physical properties of lightning are related to plume dynamics and associated electromagnetic field variations are revealed by video observations high speed and normal speed together with infrasound and high sampling rate magnetotelluric signals data show that volcanic lightning at sakurajima mainly occurs in the plume gas thrust region at a few hundred meters above the crater rim where the overpressure of the turbulent volcanic jets determines the electrification of particles generating a complex charge structure in the growing plume organization of charges may be achieved at later stages when the plume transitions from the jet phase to the convective phase comparison with atmospheric sounding and maximum plume height data show that the effect of hydrometeors on flash generation at sakurajima is negligible and can be more prudently considered as an additional factor contributing to the electrification of volcanic plumes

post equinox dynamics and polar cloud structure on uranus abstract post equinox imaging of uranus by hst keck and gemini telescopes has enabled new measurements of winds over previously sampled latitudes as well as measurements at high northern latitudes that have recently come into better view these new observations also used techniques to greatly improve signal to noise ratios making possible the detection and tracking of more subtle cloud features the 250 m s prograde jet peaking near 60 n was confirmed and more accurately characterized several long lived cloud features have also been tracked the winds pole ward of 60 n are consistent with solid body rotation at a westward prograde rate of 4 3 h with respect to uranus interior when combined with 2007 and other recent measurements it is clear that a small but well resolved asymmetry exists in the zonal profile at middle latitudes peaking at 35 where southern winds are 20 m s more westward than corresponding northern winds high s n keck ii imaging of the north polar region of uranus reveals a transition from streaky bands below 60 n to a region from 60 to nearly the north pole where widely distributed small bright spots resembling cumulus cloud fields with several isolated dark spots are the dominant style of cloud features this presents a stark contrast to 2003 detailed views of the south polar region of uranus when no discrete cloud features could be detected in comparable keck ii near ir images the pressure levels of discrete clouds estimated from spatial modulations in h and hcont images indicate that the polar cloud features are generally in the 1 3 to 2 3 bar range as are equatorial and several mid latitude features several of the brighter mid latitude features are found above the 1 2 bar level of methane condensation

the 7 september 2008 vulcanian explosion at stromboli volcano multiparametric characterization of the event and quantification of the ejecta this paper was partially supported by a research project project ingv dpc paroxysm v2 03 2007 2009 funded by istituto nazionale di geofisica e vulcanologia and by the italian civil protection

internal loading of an inhomogeneous compressible earth with phase boundaries summary we use an approach described by dehant wahr 1991 to estimate the geoid and boundary topography caused by mass loads inside the earth we show how the estimates are affected by compressibility and a radially varying density distribution and by the presence of phase boundaries with density discontinuities we compare results for earth models that have a chemical boundary at 670 km depth with those that have a phase boundary at that depth we find that the 670 km topographies predicted for models with a chemical boundary are several times larger than for models with a phase boundary depending principally on the value of the clapeyron slope in the phase case the geoid predicted in the chemical boundary case is about 30 40 per cent smaller than that predicted in the phase case the effects of compressibility and radially varying density are likely to be small we estimate the laterally varying structure inside the fluid core by computing the topography on constant potential surfaces within the core we conclude that this structure is not likely to be a complicating factor when using nutation and earth tide observations to estimate the flattening of the core mantle boundary finally we compute the inner core outer core icb topography for loading inside the mantle and for loading inside the inner core we show that in the first case the icb topography is small and dominated by long wavelengths in the second case we conclude that if the density heterogeneities inside the inner core are two orders of magnitude smaller than in the mantle the icb topography can be about 100 m peak to peak

volcanic plume electrification experimental investigation of a fracture charging mechanism although ashfall from particulate volcanic plumes is known to be highly electrically charged little is known about the charging mechanism we describe experiments designed to investigate the particle charges generated from the fracture of pumice small silicate particles were produced in the laboratory during collisions between two samples cut from pumice clasts the net charge magnitudes detected on these particles are similar to those previously measured on ashfall from volcanic plumes 10 5 to 10 6 c kg 1 this net charge is also shown to be the result of a small imbalance between the sums of individual particle charges of both polarities which are up to several orders of magnitude larger than the net charge the magnitude of both the net and single polarity specific charges were only weakly affected by changes of relative humidity but single polarity charges increased steadily with increasing sample impact velocities the dominant charging process during the experiments was that of material fracture the charging mechanism is thus interpreted to be fractoemission the release of nuclear particles from fresh crack surfaces occurring during the production of the silicate particles this implies that the electrification of volcanic plumes could be the result of brittle fragmentation of magma or pumice clasts within the upper regions of the conduit and in the jet region of the plume

an experiment to detect and locate lightning associated with eruptions of redoubt volcano abstract a commercially available lightning detection system was temporarily deployed near cook inlet alaska in an attempt to remotely monitor volcanogenic lightning associated with eruptions of redoubt volcano the system became operational on february 14 1990 lightning was detected in 11 and located in 9 of the 13 subsequent eruptions the lightning was generated by ash clouds rising from pyroclastic density currents produced by collapse of a lava dome emplaced near redoubt s summit lightning discharge flash location was controlled by topography which channeled the density currents and by wind direction in individual eruptions early flashes tended to have a negative polarity negative charge is lowered to ground while late flashes tended to have a positive polarity positive charge is lowered to ground perhaps because the charge separation process caused coarse rapid settling particles to be negatively charged and fine slow settling particles to be positively charged results indicate that lightning detection and location is a useful adjunct to seismic volcano monitoring particularly when poor weather or darkness prevents visual observation the simultaneity of seismicity and lightning near a volcano provides the virtual certainty that an ash cloud is present this information is crucial for aircraft safety and to warn threatened communities of impending tephra falls the alaska volcano observatory has now deployed a permanent lightning detection network around cook inlet

a three dimensional model of moist convection for the giant planets the jupiter case abstract we present a three dimensional cloud model designed for the study of formation and evolution of moist convective storms on the giant planets this is a finite difference model that solves the dynamic and thermodynamic equations forward in time under the anelastic approximation including microphysics in a parameterized form three dimensional modeling is needed to include the dynamical effects of the vertical and meridional ambient wind shears and the coriolis force on the storm onset and evolution the model is designed to run on the four giant planets to compare how moist convection operates in each case in this paper we present the results for jupiter water ammonia storms under a variety of conditions several improvements in the mathematical formulation and in the numerical methods and an update of the input values e g the thermal profile and gas abundances with respect to previous models have been incorporated we show that under the appropriate relative humidity conditions and particulate precipitation it is possible to create visible storms even with a small deep water abundance of 0 2 times the solar value the effect of the vertical wind shear is important as it is on earth in controlling the structure of the cloud its growing ratio and the local wind field but it has a small influence on the upper level reached by the storm the distribution of the convective cells created in the presence of a vertical wind shear resembles the pattern of mesoscale storms recently observed by galileo

normal mode sensitivity to earth s d layer and topography on the core mantle boundary what we can and cannot see the core mantle boundary cmb is earth s most profound internal boundary separating the liquid iron outer core and the solid silicate mantle the detailed structure near the cmb has a major influence on mantle convection and the evolution of the core seismic observations such as topography on the cmb thin ultra low velocity zones ulvzs seismic anisotropy and the anticorrelation between shear wave and bulk sound velocity heterogeneities have mainly been made using body waves and are still poorly constrained we investigate the sensitivity of earth s free oscillations to these features and specifically show how large individual anomalies must be for them to be observable in addition we discuss the possible trade offs between these different lowermost mantle structures although modes have strong sensitivity to all the structures inserted the results illustrate the limits of what normal modes can resolve our tests show that i even small scale features such as ulvzs with a thickness larger than 19 km can be observed as long as their distribution contains a long wavelength component ii the peak to peak amplitude of cmb topography has a larger influence than its pattern and has to be smaller than 5 km to fit the data iii the effect of scaling between shear wave velocity and density anomalies is less constrained but a laterally varying pattern is implied by a simple test suggesting the presence of chemical variations iv a strong trade off exists between anisotropy in compressional wave velocity and incidence angle whereas shear wave anisotropy is less observable these findings provide valuable information for future normal mode studies on structures in earth s lowermost mantle and their trade offs

color and the vertical structure in jupiter s belts zones and weather systems abstract radiative transfer analysis was performed with data taken by the galileo spacecraft solid state imager ssi during its nominal mission december 1995 to december 1997 the objective is to use the methane band 727 and 889 nm and color 410 and 756 nm sensitivities to identify the vertical position of cloud absorption that leads to coloration earlier work banfield et al 1998 icarus 135 230 250 with only the near ir continuum and methane band images yielded information about the vertical distribution of cloud scatterers but no information on the wavelength dependence of cloud absorption the new analysis employs the same parameter retrieval algorithm but adds the 410 nm wavelength under the assumption that the 410 nm absorption by cloud particles is indicative of spectrally broad blue absorption the new channel gives color information the primary color difference between the dark north equatorial belt neb and the brighter equatorial zone ez appears to be in the tropospheric haze layer s 410 nm single scattering albedo this layer extends through the stably stratified region approximately from 200 to 800 mbars the base of the haze layer is slightly deeper in the neb by about 200 mbars than in the ez and a variable thickness white cloud layer at the base of the haze exists in both regions but is about five times optically thicker in the ez within the ez slight color variation is seen with latitude again due to 410 nm single scattering albedo variation in the haze layer anomalous regions such as the great red spot and a 5 m hot spot are modeled showing additional variations in the structure and color of the tropospheric haze deeper clouds with pressures of 1 7 bars are seen in occasional clearings but their opacity and color are not well constrained by the data

mid infrared mapping of jupiter s temperatures aerosol opacity and chemical distributions with irtf texes abstract global maps of jupiter s atmospheric temperatures gaseous composition and aerosol opacity are derived from a programme of 5 20 m mid infrared spectroscopic observations using the texas echelon cross echelle spectrograph texes on nasa s infrared telescope facility irtf image cubes from december 2014 in eight spectral channels with spectral resolutions of r 2000 12 000 and spatial resolutions of 2 4 latitude are inverted to generate 3d maps of tropospheric and stratospheric temperatures 2d maps of upper tropospheric aerosols phosphine and ammonia and 2d maps of stratospheric ethane and acetylene the results are compared to a re analysis of cassini composite infrared spectrometer cirs observations acquired during cassini s closest approach to jupiter in december 2000 demonstrating that this new archive of ground based mapping spectroscopy can match and surpass the quality of previous investigations and will permit future studies of jupiter s evolving atmosphere the visibility of cool zones and warm belts varies from channel to channel suggesting complex vertical variations from the radiatively controlled upper troposphere to the convective mid troposphere we identify mid infrared signatures of jupiter s 5 m hotspots via simultaneous m n and q band observations which are interpreted as temperature and ammonia variations in the northern equatorial zone and on the edge of the north equatorial belt neb equatorial plumes enriched in nh3 gas are located south east of nh3 desiccated hotspots on the edge of the neb comparison of the hotspot locations in several channels across the 5 20 m range indicate that these anomalous regions tilt westward with altitude aerosols and ph3 are both enriched at the equator but are not co located with the nh3 plumes the equatorial temperature minimum and ph3 aerosol maxima have varied in amplitude over time possibly as a result of periodic equatorial brightenings and the fresh updrafts of disequilibrium material temperate mid latitudes display a correlation between mid ir aerosol opacity and the white albedo features in visible light i e zones we find hemispheric asymmetries in the distribution of tropospheric ph3 stratospheric hydrocarbons and the 2d wind field estimated via the thermal wind equation that suggest a differing efficiency of mechanical forcing e g vertical mixing and wave propagation between the two hemispheres that we argue is driven by dynamics rather than jupiter s small seasonal cycle jupiter s stratosphere is notably warmer at northern mid latitudes than in the south in both 2000 and 2014 although the latter can be largely attributed to strong thermal wave activity near 30 n that dominates the 2014 stratospheric maps and may be responsible for elevated c2h2 in the northern hemisphere a vertically variable pattern of temperature and windshear minima and maxima associated with jupiter s quasi quadrennial oscillation qqo is observed at the equator in both datasets although the contrasts were more subdued in 2014 large scale equator to pole gradients in ethane and acetylene are superimposed on top of the mid latitude mechanically driven maxima with c2h2 decreasing from equator to pole and c2h6 showing a polar enhancement consistent with a radiatively controlled circulation from low to high latitudes cold polar vortices beyond 60 latitude can be identified in the upper tropospheric and lower stratospheric temperature maps suggesting enhanced radiative cooling from polar aerosols finally compositional mapping of the great red spot confirms the local enhancements in ph3 and aerosols the north south asymmetry in nh3 gas and the presence of a warm southern periphery that have been noted by previous authors

the retrieval of cloud structure maps in the equatorial region of jupiter using a principal component analysis of galileo nims data abstract the cloud structure of the jovian atmosphere at pressures less than 2 bars has previously been estimated using near infrared observations such as those by both the solid state imager ssi and near infrared mapping spectrometer nims instruments on board the galileo spacecraft unfortunately complete near infrared spectra such as those measured by nims take a long time to be analyzed with multiple scattering radiative transfer models and thus it has until now been rather difficult to use these data to produce wide area cloud maps in this paper we show how principal component analysis may be employed to isolate a small number of empirical orthogonal functions eofs from spectra of jupiter made by galileo nims these eofs may be used to represent the variance of real nims spectra to a high degree of accuracy and with good noise and drop out discrimination because of this a small set of representative spectra may then be calculated using these eofs and input into a retrieval model that generates a table of fitted cloud profiles for each case this approach avoids the long times required for analyzing a large number of spectra with full multiple scattering radiative transfer models and allows us to represent the variability of the 3000 spectra contained in the observations of the north equatorial belt neb used in this study with only 75 representative spectra the cloud structures fitted to these representative spectra were interpolated for the spectra found at individual locations in the measured nims data set to produce maps of cloud opacity and mean particle size we find that the dominant opacity variation anticorrelated with 5 m brightness exists in the 1 2 bar pressure range the distribution of the cloud at 0 72 bars is mapped and found to be more zonally diffuse than the lower clouds we find at least one 2000 km sized deep convective cloud in the neb vertically extending to all the pressure levels that can be sensed by nims

methane depletion in both polar regions of uranus inferred from hst stis and keck nirc2 observations abstract from space telescope imaging spectrograph stis observations of uranus in 2012 when good views of its north polar regions were available we found that the methane volume mixing ratio declined from about 4 at low latitudes to about 2 at 60 80 n this depletion in the north polar region of uranus in 2012 is similar in magnitude and depth to that found in the south polar regions in 2002 this similarity is remarkable because of the strikingly different appearance of clouds in the two polar regions we have never seen any obvious signs of convective activity in the south polar region while the north has been peppered with numerous small clouds thought to be of convective origin keck and hubble space telescope imaging observations close to equinox at wavelengths of 1080 nm and 1290 nm with different sensitivities to methane and hydrogen absorption but similar vertical contribution functions imply that the depletions were simultaneously present in 2007 and at least their gross character is probably a persistent feature of the uranus atmosphere the depletion appears to be mainly restricted to the upper troposphere with the depth increasing poleward from about 30 n reaching 4 bars at 45 n and perhaps much deeper at 70 n where it is not well constrained by our observations the latitudinal variations in degree and depth of the depletions are important constraints on models of meridional circulation our observations are qualitatively consistent with previously suggested circulation cells in which rising methane rich gas at low latitudes is dried out by condensation and sedimentation of methane ice particles as the gas ascends to altitudes above the methane condensation level then is transported to high latitudes where it descends and brings down methane depleted gas since this cell would seem to inhibit formation of condensation clouds in regions where clouds are actually inferred from spectral modeling it suggests that sparse localized convective events may be important in cloud formation a more complex meridional circulation pattern may be necessary to reproduce the observed cloud distribution but microwave observations appear to be most compatible with a single deep circulation cell the small scale latitudinal variations we found in the effective methane mixing ratio between 55 n and 82 n have significant inverse correlations with zonal mean latitudinal variations in cloud reflectivity in near ir keck images taken before and after the hst observations if the ch4 h2 absorption ratio variations are interpreted as local variations in para fraction instead of methane mixing ratio we find that downwelling correlates with reduced cloud reflectivity while there has been no significant secular change in the brightness of uranus at continuum wavelengths between 2002 and 2012 there have been significant changes at wavelengths sensing methane and or hydrogen absorption with the southern hemisphere darkening considerably between 2002 and 2012 by 25 at mid latitudes near 827 nm for example while the northern hemisphere has brightened by 25 at mid latitudes at the same wavelength

the evolving flow of jupiter s white ovals and adjacent cyclones abstract we present results regarding the dynamical meteorology of jupiter s white ovals at different points in their evolution starting from the era with three white ovals fa bc and de galileo continuing to the post merger epoch with only one oval ba cassini and finally to oval ba s current reddened state new horizons we demonstrate that the dynamics of their flow have similarly evolved along with their appearance in the galileo epoch oval de had an elliptical shape with peak zonal wind speeds of 90 m s 1 in both its northern and southern peripheries during the post merger epoch oval ba s shape was more triangular and less elliptical than oval de in addition to widening in the north south direction its northern periphery was 20 m s 1 slower and its southern periphery was 20 m s 1 faster than oval de s flow during the galileo era finally in the new horizons era the reddened oval ba had evolved back to a classical elliptical form the northern periphery of oval ba increased in speed by 20 m s 1 from cassini to new horizons ending up at a speed nearly identical to that of the northern periphery of oval de during galileo however the peak speeds along the southern rim of the newly formed oval ba were consistently faster than the corresponding speeds in oval de and they increased still further between cassini and new horizons ending up at 140 150 m s 1 relative vorticity maps of oval ba reveal a cyclonic ring surrounding its outer periphery similar to the ring present around the great red spot the cyclonic ring around oval ba in 2007 appears to be moderately stronger than observed in 1997 and 2001 suggesting that this may be associated with the coloration of the vortex the modest strengthening of the winds in oval ba the appearance of red aerosols and the appearance of a turbulent cyclonic feature to oval ba s northwest create a strong resemblance with the great red spot from both a dynamical and morphological perspective in addition to the white ovals we also measure the winds within two compact cyclonic regions one in the galileo data set and one in the cassini data set in the images these cyclonic features appear turbulent and filamentary but our wind field reveals that the flow manifests as a coherent high speed collar surrounding relatively quiescent interiors our relative vorticity maps show that the vorticity likewise concentrates in a collar near the outermost periphery unlike the white ovals which have peak relative vorticity magnitudes near the center of the vortex the cyclones contain several localized bright regions consistent with the characteristics of thunderstorms identified in other studies although less studied than their anticyclonic cousins these cyclones may offer crucial insights into the planet s cloud level energetics and dynamical meteorology

viscoelastic mantle density heterogeneity and core mantle topography summary starting with the model of mantle density heterogeneity derived by ricard et al 1993 which uses plate motion reconstructions under the assumption that subducted slabs sink vertically into the mantle we model the temporal evolution of these internal loads we investigate the viscoelastic deformation of the earth due to this time dependent excitation source using a love number formalism for a linear viscoelastic mantle with a maxwell model of rheology we are especially interested in the deep earth viscoelastic deformation such as the radial displacement that appears at the core mantle boundary and we compare the calculated topography with that proposed by seismologists

keck adaptive optics images of jupiter s north polar cap and northern red oval abstract we present observations at near infrared wavelengths 1 5 m of jupiter s north polar region and northern red oval nn lrs 1 the observations were taken with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck telescope on ut 21 august 2010 at 5 m jupiter s disk reveals considerable structure including small bright rings which appear to surround all small vortices it is striking though that no such ring is seen around the northern red oval in de pater et al 2010a icarus 210 742 762 we showed that such rings also exist around all small vortices in jupiter s southern hemisphere and are absent around the great red spot and red oval ba we show here that the vertical structure and extent of the northern red oval is very similar to that of jupiter s red oval ba these new observations of the northern red oval therefore support the idea of a dichotomy between small and large anticyclones in which ovals larger than about two rossby deformation radii do not have 5 m bright rings in de pater et al 2010a icarus 210 742 762 we explained this difference in terms of the secondary circulations within the vortices we further compare the brightness distribution of our new 5 m images with previously published radio observations of jupiter highlighting the depletion of nh 3 gas over areas that are bright at 5 m

analysis of magnetic data over the abakaliki anticlinorium of the lower benue trough nigeria abstract two dimensional spectral analysis of aeromagnetic data has been used to determine the mean depths to buried magnetic basement rocks in the abakaliki anticlinorium of the lower benue trough in nigeria the average thickness of the sedimentary cover overlying the basement which may contain petroleum reservoirs has thus been determined the results indicate a two depth source model with the depth to the deeper sources identified with the crystalline basement varying between 1200 and 2500 m isolated linear magnetic features which are prominent on the aeromagnetic maps were also studied in detail the anomalies over such features which in many cases have spatial dimensions that are greater than 10 km were modelled in terms of dyke like bodies using non linear optimization techniques the results obtained from these studies compare favourably with those from gravity and ground magnetic investigations carried out in the are the sediment thickness in the area the occurrence of numerous intrusive bodies and the deformational history of the sedimentary rock sequences in the abakaliki anticlinorium suggest that this part of the benue trough may not hold much promise in terms of hydrocarbon accumulation

inference of core mantle boundary topography from isc pcp and pkp traveltimes we invert isc pcp and pkp absolute and differential traveltimes in an attempt to infer the long wavelength topography of the core mantle boundary cmb the data selection and processing methods are described and evaluated these travel time data are very noisy and the geographic distribution of the data is highly non uniform inhibiting reliable inference of cmb topography spatial averaging enhances the coherent component of the residual variance related to heterogeneity however the random component of the variance is much larger than the coherent component we show that for pcp data the coherent signal due to mantle heterogeneity overshadows that arising from the cmb and that the effects of mantle heterogeneity are mapped into our inferred cmb solutions the pcp data are not correlated across the spatial averaging bins and seem to have a strong bias due to small scale structure and or noise the non uniform geographic sampling of the data plays a role in the mapping of mantle heterogeneity onto the cmb spatial patterns of cmb models inferred from different phases do not agree amplitudes of seismically inferred cmb undulations vary greatly the sensitivity of inferred cmb models to the processing spatial averaging procedure and inversion techniques are investigated topographic amplitudes increase strongly with increasing input residual variance the power spectrum of inferred topography indicates that there are unmodelled heterogeneities that must be described with spherical harmonics of degree 6 and higher based on this work we conclude that reliable inference of long wavelength cmb topography is not likely with the current isc data set or with a spherical harmonic expansion truncated to degree and order 6

galileo images of lightning on jupiter in october and november of 1997 the galileo solid state imager ssi detected lightning from 26 storms on the night side of jupiter more than half the surface area of the planet was surveyed the data include images of lightning against moonlit clouds illuminated by light from io and images of the same storm on the day and night sides the spatial resolution ranged from 23 to 134 km per pixel while the storms ranged in size up to 1500 km most storms were imaged more than once and they typically exhibit many flashes per minute the storms occur only in areas of cyclonic shear and near the centers of westward jets latitudes near 50 in both hemispheres are particularly active although the northern hemisphere has more lightning overall the greatest optical energy observed in a single flash was 1 6 10 10 j which is several times larger than terrestrial superbolts the average optical power per unit area is 3 10 7 w m 2 which is close to the terrestrial value the limited color information is consistent with line and continuum emission from atomic hydrogen and helium the intensity profiles of resolved lightning strikes are bell shaped with the half width at half maximum ranging from 45 to 80 km we used these widths to infer the depth of the strikes assuming that the appearance of each is the result of light scattering from a point source below the cloudtops we conclude that lightning must be occurring within or below the jovian water cloud the occurrence of lightning in regions of cyclonic shear has important implications for the dynamics of jupiter s atmosphere

topographic core mantle coupling in geodynamo modeling a 3 dimensional fully nonlinear numerical geo dynamo model is used to study the core mantle coupling arising from a non hydrostatic pressure field acting on an aspherical core mantle boundary cmb based on a seismo logical model the simulation results demonstrate that the topographic coupling torque is close to being proportional to the square of the amplitude of the cmb topography we conclude that the contribution of the topographic coupling to the total torque that is responsible for the axial angular momentum transfer on decadal timescales for the decadal length of day variation is significant only if the amplitude of the cmb topography is considerably larger than 3 km inferred from seismological evidence

tangentially geostrophic flow at the core mantle boundary compatible with the observed geomagnetic secular variation the large scale component of the flow abstract we present a method for determining the large scale component of a tangentially geostrophic flow beneath the core mantle boundary compatible with magnetic secular variation observations we use a tangentially geostrophic basis to ensure the geostrophy of the motion the fit of the secular variation sv generated by the motion to the observed sv in fact sv models is adequate taking into account the existing error level as in any horizontal geostrophic motion the flow is expressed as a sum of two independent tangentially geostrophic flows a zonal component which is toroidal and a non zonal component which is directly linked with the motions deeper in core the flow derived for the recent epoch 1970 1985 presents interesting symmetry properties the non zonal velocities are the same at two antipodal points while the zonal velocities are the same at two points symmetrical about the equator the non zonal component of the flow is more vigorous than the zonal one the consoidal ingredient though weaker than the toroidal ingredient is essential and indicates strong vertical motion at depth in low latitude areas the sv is actually compatible with a geostrophic motion at the core mantle boundary and appears to be mainly due to the action of the non zonal component of the flow

meteorology of jupiter s equatorial hot spots and plumes from cassini we present an updated analysis of jupiter s equatorial meteorology from cassini observations for two months preceding the spacecraft s closest approach the imaging science subsystem iss onboard regularly imaged the atmosphere we created time lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes hot spots are relatively cloud free regions that emit strongly at 5 lm improved knowledge of these features is crucial for fully understanding galileo probe measurements taken during its descent through one hot spots are quasistable rectangular dark areas on visible wavelength images with defined eastern edges that sharply contrast with surrounding clouds but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes hot spots exhibit significant variations in size and shape over timescales of days and weeks some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots impressive bright white plumes occupy spaces in between hot spots compact cirrus like scooter clouds flow rapidly through the plumes before disappearing within the dark areas these clouds travel at 150 200 m s 1 much faster than the 100 m s 1 hot spot and plume drift speed this raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip if a downward branch of an equatorially trapped rossby wave controls the overall appearance of hot spots however the westward phase velocity of the wave leads to underestimates of the true jet stream speed

ammonia in jupiter s troposphere from high resolution 5 μm spectroscopy jupiter s tropospheric ammonia nh3 abundance is studied using spatially resolved 5 m observations from crires a high resolution spectrometer at the european southern observatory s very large telescope the high resolving power r 96 000 allows the line shapes of three nh3 absorption features to be resolved we find that within the 1 4 bar pressure range the nh3 abundance decreases with altitude the instrument slit was aligned north south along jupiter s central meridian allowing us to search for latitudinal variability there is considerable uncertainty in the large scale latitudinal variability as the increase in cloud opacity in zones compared to belts can mask absorption features however we do find evidence for a strong nh3 enhancement at 4 6 n consistent with a localised ammonia plume on the southern edge of jupiter s north equatorial belt

the 2009 2010 fade of jupiter s south equatorial belt vertical cloud structure models and zonal winds from visible imaging abstract the south equatorial belt seb of jupiter is known to alternate its appearance at visible wavelengths from a classical belt like band most of the time to a short lived zone like aspect which is called a fade of the belt hereafter sebf the albedo change of the seb is due to a change in the structure and properties of the clouds and upper hazes recent works based on infrared observations of the last sebf have shown that the aerosol density below 1 bar increased in parallel with the reflectivity change however the nature of the change in the upper clouds and hazes that produces the visible reflectivity change and whether or not this reflectivity change is accompanied by a change in the winds at the upper cloud level remained unknown in this paper we focus in the near ultraviolet to near infrared reflected sunlight 255 953 nm to address these two issues we characterize the vertical cloud structure above the ammonia condensation level from hubble space telescope images and the zonal wind velocities from long term high quality images coming from the international outer planet watch database both during the seb and sebf phases we show that reflectivity changes do not happen simultaneously in this wavelength range but they start earlier in the most deep sensing filters and end in 2010 with just minor changes in those sensing the highest particle layers our models require a substantial increase of the optical thickness of the cloud deck at 1 0 0 4 bar from cloud 6 2 in july 2009 seb phase to semiinfinite at visual wavelengths in 2010 sebf upper tropospheric particles 240 1400 mbar are also required to become substantially reflectant and their single scattering albedo in the blue changes from 0 0 905 0 005 in november 2009 to 0 0 95 0 01 in june 2010 no significant changes were found in the cloud top heights or in the particle density of the tropospheric haze the disturbance travels from the levels below 3 bar to a level about 400 100 mbar we derive an upward velocity of 0 15 0 05 cm s in agreement with a diffusive process in jupiter s upper troposphere requiring a mean eddy coefficient k 8 105 cm2 s 1 on the other hand cloud tracking on the iopw imaging showed no significant changes in the zonal wind profile between the seb and sebf stages as in other visually huge changes in jupiter s cloud morphology and structure the wind profile remains robust possibly indicating a deeply rooted dynamical regime

cassini imaging of jupiter s atmosphere satellites and rings the cassini imaging science subsystem acquired about 26 000 images of the jupiter system as the spacecraft encountered the giant planet en route to saturn we report findings on jupiter s zonal winds convective storms low latitude upper troposphere polar stratosphere and northern aurora we also describe previously unseen emissions arising from io and europa in eclipse a giant volcanic plume over io s north pole disk resolved images of the satellite himalia circumstantial evidence for a causal relation between the satellites metis and adrastea and the main jovian ring and information on the nature of the ring particles

the structure of the core mantle boundary from diffracted waves diffracted p and s waves pd sd traveling around the core mantle boundary cmb of the earth give us information about the velocity structure and therefore the thermochemistry of d the base of the earth s mantle by examining pd and sdarrivals we determined the apparent ray parameter for different regions at the base of the mantle by comparing the data slownesses to those found from reflectivity synthetic seismograms we were able to quantify d average velocities using these averaged velocities with a thermochemical modeling of lower mantle minerals using a birch mumaghan equation of state we have been able to make chemical and physical inferences as to the causes of lateral variations at the cmb examinations found significant lateral heterogeneity at the base of the mantle amounting to 4 for both p and s velocities these velocities did not always vary in parallel and the poisson ratio varied regionally by almost 6 the most unusual region of the cmb found was under indonesia where velocities 3 slower than the preliminary reference earth models were found adjacent to a region of faster than average velocities these regions currently correspond to areas of core up welling and down welling respectively found by voorhies 1986 which if mostly held in place by core mantle coupling might cause a flux of heat and iron into the mantle making the anomaly both thermally and chemically derived at the cmb under the northern pacific rim the fastest shear velocities were found but the same region yielded slower than average p velocities while the presence of fast shear velocities here would support the idea that we are seeing the cold dregs of mantle convection perhaps continuing down from the north pacific subduction zones the presence of slow p velocities suggests additional complications our thermochemical modeling suggests that the d poisson ratio is very sensitive to variations in the silicate oxide ratio and that a decrease in the amount of perovskite relative to magnesiowustite may play an important role in this region

modeling jupiter s cloud bands and decks 2 distribution and motion of condensates abstract a simple jovian cloud scheme has been developed for the oxford planetary unified model system opus nh 3 ice nh 4 sh solid h 2 o ice and h 2 o liquid clouds have been modeled in southern hemisphere limited area simulations of jupiter we found that either three or four of the condensates existed in the model for a deep atmospheric water abundance close to solar composition an nh 3 ice deck above 0 7 bar an nh 4 sh solid deck above 2 5 bar and a h 2 o liquid deck with a base at about 7 5 bar and frozen cloud tops formed if a depleted deep water abundance is assumed however a very compact cloud structure develops where an h 2 o ice cloud forms by direct sublimation above 3 bar the condensates constitute good tracers of atmospheric motion and we have confirmed that zonal velocities determined from manual feature tracking in the modeled cloud layers agree reasonably well with the modeled zonal velocities dense and elevated clouds form over latitudes with strong atmospheric upwelling and depleted clouds exist over areas with strong downwelling in the nh 3 ice deck this leads to elevated cloud bands over the zones in the domain and thin clouds over the belts which is consistent with the observationally deduced distribution due to changes in the vertical velocity pattern in the deeper atmosphere the nh 4 sh solid and water cloud decks are more uniform this modeled cloud structure thus includes the possibility of more frequent water cloud observations in belts as this deeper deck could be more easily detected under areas with thin nh 3 ice clouds large scale vortices appeared spontaneously in the model and were characterized by elevated nh 3 ice clouds as expected from observations these eddies leave the most discernible imprint on the lighter condensate particles of the uppermost layer

evaluating stratiform cloud base charge remotely stratiform clouds acquire charge at their upper and lower horizontal boundaries due to vertical current flow in the global electric circuit cloud charge is expected to influence microphysical processes but understanding is restricted by the infrequent in situ measurements available for stratiform cloud bases below 1 km in altitude the cloud base charge modifies the surface electric field beneath allowing a new method of remote determination combining continuous cloud height data during 2015 2016 from a laser ceilometer with electric field mill data cloud base charge is derived using a horizontal charged disk model the median daily cloud base charge density found was 0 86 ncm 2 from 43 days data this is consistent with a uniformly charged region 40 m thick at the cloud base now confirming that negative cloud base charge is a common feature of terrestrial layer clouds this technique can also be applied to planetary atmospheres and volcanic plumes

zonal jets as transport barriers in planetary atmospheres abstract the connection between transport barriers and potential vorticity pv barriers in pv conserving flows is investigated with a focus on zonal jets in planetary atmospheres a perturbed pv staircase model is used to illustrate important concepts this flow consists of a sequence of narrow eastward and broad westward zonal jets with a staircase pv structure the pv steps are at the latitudes of the cores of the eastward jets numerically simulated solutions to the quasigeostrophic pv conservation equation in a perturbed pv staircase flow are presented these simulations reveal that both eastward and westward zonal jets serve as robust meridional transport barriers the surprise is that westward jets across which the background pv gradient vanishes serve as robust transport barriers a theoretical explanation of the underlying barrier mechanism is provided it is argued that transport barriers near the cores of westward zonal jets across which the background pv gradient is small are found in jupi

the contribution of experimental volcanology to the study of the physics of eruptive processes and related scaling issues a review abstract the experimental approach has become a major tool increasingly used by volcanologists in recent decades to investigate the physics of eruptive processes in complement to field and theoretical works researchers have developed various methodologies to study volcanic phenomena at reduced length scale the works involve natural or analogue materials and their types range from first order tests to identify fundamental processes and make qualitative comparison with field observations to more sophisticated experiments in which precise data obtained in a controlled environment can be used to validate outputs of theoretical models scaling is a central issue to ensure dynamic similarity between the small scale experiments and the large scale volcanic phenomena when natural conditions cannot be simulated due to inherent length scale difference and or technical limitations in this respect dimensionless numbers are used to map physical regimes and to define scaling laws which allow experimental results to be extrapolated to natural scale this review presents the variety of experimental studies conducted to investigate subterraneous and aerial volcanic phenomena involving in particular fluid particle mixtures we focus on the major scaling issues and the physical regimes investigated and we also highlight in a historical perspective some of the major advances achieved through experimental studies finally we conclude on some perspectives for future works

mapping s velocity heterogeneities in the d region from smks differential travel times abstract seismic velocity heterogeneities in the d region are studied using differential travel time residuals between smks waves previous studies indicate that regional variations in the propagation times of these waves are not due to the propagation through the liquid core furthermore they are only weakly influenced by the topography of the core mantle boundary cmb thus the differential travel time anomalies are interpreted as the result of lower mantle heterogeneity we compiled all the available published data and added new observations of travel times from geoscope stations we thus obtained 807 s2ks sks and 209 s3ks s2ks differential times differential travel time residuals with respect to the mean earth model prem preliminary reference earth model are corrected for ellipticity and for mantle heterogeneity down to 2590 km depth 300 km above the cmb using the 3 dimensional s wave velocity model sh12 wm13 this model gives a 10 variance reduction of the residuals the remaining variance of residuals is higher for s2ks sks than for s3ks s2ks which is consistent with a d origin for the heterogeneities the data are inverted for regional variations using a least squares analysis assuming a single layer d structure 300 km thick the earth is divided in 150 equal area sectors about 115 of which are sampled by four rays or more we performed inversions using 18 different geographic grids and averaged the results so as to minimize the artefacts induced by imposing artificial block boundaries the velocity heterogeneity map though affected by the poor sampling of the oceans reveals significant long wavelength structure with velocity perturbations exceeding 3 with respect to a reference velocity which is slightly lower than the prem one this heterogeneity map is consistent with the results from most of previous studies global as well as regional the location of some of the high velocity anomalies coincides with places where subducted slab material may have accumulated at the cmb these high velocity heterogeneities are also generally correlated with places where a discontinuous velocity increase of several per cent has been detected at the top of d

short time electrical effects during volcanic eruption experiments and field measurements laboratory experiments on the fragmentation and expansion of magmatic melt have been performed using remelted volcanic rock at magmatic temperatures as magma simulant a specially designed dc amplifier in combination with high speed data recording was used to detect short time electrostatic field effects related to the fragmentation and expansion history of the experimental system as documented by simultaneous force and pressure recording as well as by high speed cinematography it was found that 1 the voltage time ratio of electrostatic field gradients 100 to 104 v s reflects different physical mechanisms of fragmentation and expansion and 2 the maximum voltage measured in 1 m distance 0 1 to 180 v can be correlated with the intensity of the respective processes based on these experimental results a field method was developed and tested at stromboli volcano in italy a 0 8 m rod antenna was used to detect the dc voltage against local ground i e the electrostatic field gradient at a distance of 60 to 260 m from the respective vent upwind position of the detection site was chosen to prevent interference caused by contact of charged ash particles with the antenna a standard 8 hz geophone was used to detect the accompanying seismicity three types of volcanic activity occurred during the surveillance operation two of these could be clearly related to specific electrical and seismical signals a typical delay time was found between the electrical and the seismical signal corresponding to the seismic velocity within the crater deposits using a simple first order electrostatic model the field measurements were recalibrated to the laboratory scale comparison of field and laboratory data at first approximation revealed striking similarities thus encouraging the further development of this technique for real time surveillance operation at active volcanoes

rapid fluid disruption a source for self potential anomalies on volcanoes self potential sp anomalies observed above suspected magma reservoirs dikes etc on various volcanoes kilauea hawaii mount unzen japan piton de la fournaise reunion island miyake jima japan result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity these sp anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained we propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization disruption as liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions both charge generation and local increase in electrical resistivity by removal of fluids should occur we report laboratory observations of electric fields in hot rock samples generated by pulses of fluid water through the rock at atmospheric pressure these indicate the relative amplitudes of rapid fluid disruption rfd potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign above vaporization temperatures rfd effects of positive sign in the direction of gas flow dominate whereas below these temperatures effects of negative sign dominate this suggests that the primary contribution to observed self potential anomalies arises from gas related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport at lower temperatures the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and rfd effects from high pressure but low temperature co 2 and so 2 gas flow ripping water molecules from saturated crustal rocks if charge generation is continuous as could well occur above a newly emplaced dike positive static potentials will be set up that could be sustained for many years and the simplest method for identifying these hot active regions would be to identify the sp anomalies they generate

moist convection as an energy source for the large scale motions in jupiter s atmosphere jupiter s dominant large scale weather patterns dimensions 10 000 km are zonal jets and long lived ovals the jets have been flowing east and west at constant speeds of up to 180 m s 1 for over 100 years these jets receive energy from small scale eddies which pump eastward momentum into the eastward jets and westward momentum into the westward jets this momentum transfer was predicted by numerical models before it was observed on jupiter the large ovals roll between the jets in an anticyclonic direction clockwise in the northern hemisphere and counterclockwise in the southern hemisphere where they regularly assimilate small anticyclonic eddies but from where the eddies receive their energy has been an open question here we argue that the eddies which ultimately drive both the jets and the ovals receive their energy from moist convection this hypothesis is consistent with observations of jovian lightning which is an indicator of moist convection it also explains the anticyclonic rotation and poleward drift of the eddies and suggests patterns of upwelling and downwelling that resemble the patterns of large scale axisymmetric overturning in the earth s atmosphere

measurements of electric charge distribution in volcanic plumes at sakurajima volcano japan measurements of perturbations in the atmospheric potential gradient around volcanic plumes at multiple from two to five sites and measurements of the charge mass ratio of ash particles falling from volcanic plumes were carried out at sakurajima volcano japan results from 28 and 29 october 1995 show that the nature of the perturbations depends on the intensity of plume activity although plume activity was vigorous on 28 october negative perturbations were predominant as plume activity peaked the magnitude of negative perturbations decreased just below the plume and increased at an off axis site during the peak period positively charged ash particles fell out from the plume this suggests that the active plume dominantly contained negatively charged materials and that positively and negatively charged materials were added to the lower and upper parts of the plume respectively during the peak period on the other hand as plume activity became less vigorous on 29 october the perturbations were characterized by a positive anomaly followed by a negative anomaly because wind velocity increased with altitude that day we infer that positive and negative charges were distributed in the upper and lower parts of the plume respectively the differences in perturbations observed on 28 and 29 october suggest that volcanic plumes are generally composed of three parts an upper part with positively charged gas and aerosol a middle part with negatively charged fine ash particles and a lower part with positively charged coarse ash particles the compilation of present and previous results from sakurajima and other volcanoes indicates that the effect of the negative charge in the middle part was predominant in most cases although positive perturbations caused by the upper part were observed around some weak plumes the effect of positively charged particles in the lower part was observable only when plume activity was sufficiently strong because positively charged coarse particles tended to fall out near the vent

volcanic plume monitoring using atmospheric electric potential gradients by monitoring perturbations of the natural atmospheric electric potential gradient it is possible to detect and track particle laden volcanic plumes the perturbations are produced by electrical charge that resides on the solid particles and liquid droplets of the plume and the ions within it a network of potential gradient monitoring stations around a volcano can provide data on eruption time magnitude plume dispersion direction and areas of ashfall our laboratory experiments have produced electrically charged ash by fragmenting pumice these results support the theory that charging is due to the magma fragmentation process and should therefore be ubiquitous in all particulate volcanic plumes

convective growth rates of equatorial features in the jovian atmosphere the first results of measurements of divergence and vertical velocity of cloud features in the atmosphere of jupiter are presented from analyses of voyager images performed using the interactive planetary imaging processing system at university college london active equatorial plumes are found to have typical divergences of 1 2 10 5s 1 and vertical velocities of 20 40 cm s 1 during the observational periods examined these plumes are considerably more active than the bright albedo features in the turbulent regions of the jovian north and south equatorial belts

the effects of dynamics on the triboelectrification of volcanic ash lightning is often observed during explosive volcanic eruptions and the charging processes associated with these displays have been attributed to several mechanisms in this work we delineate a set of experiments designed to quantify silicate based triboelectric charging in the volcanic context using natural samples from three different volcanoes we show that the rate of triboelectrification in a fluidized bed depends on the energy input into the granular system experiments are conducted employing nonintrusive electrostatic sensors ensuring that all charge exchange arises solely from particle particle collisions at higher fluidization energies particles undergo more frequent and energetic collisions facilitating the transfer of charge this finding implies that triboelectric charging could help promote charging in regions of the eruptive system that contain numerous particle particle collisions such as the conduit and gas thrust regions our experiments also suggest that surface charge density is capped at least in part by atmospheric conditions specifically the breakdown characteristics of the gas

interpretation of galileo probe data and implications for jupiter s dry downdrafts the galileo probe found the jovian abundance of h 2s to be 30 solar at the 8 bar level while the abundance of water was less than 3 solar at 12 bars from 8 to 20 bars h 2s increased to three times solar and water apparently increased as well since h 2s and water condense at 2 and 5 bars respectively the probe probably entered a dry downdraft wherein dry air above 2 bars is advected to 12 bars or deeper owen et al 1996 eos spring suppl 77 s171 this is consistent with the fact that the probe entered the south edge of a 5 m hot spot a local region of jupiter s atmosphere known from spectral modeling to be unusually low in cloud abundance orton et al 1996 science 272 839 we use basic physical constraints to address three problems raised by galileo probe data first it is unclear how the hypothesized downdraft remains dry since simple models of convection preclude dessication below the 2 and 5 bar condensation levels we suggest that to suppress moist plumes from below the downdraft must be of low density below 5 bars and hence thermally indirect requiring mechanical forcing from other parts of the atmosphere second if geostrophic balance holds the galileo probe winds imply that the hot spot north of the probe site contains a stable layer from 1 to 5 bars this is inconsistent with a downwelling since downwellings should be adiabatic below 2 bars due to the low radiative flux divergence we show that when the centripetal acceleration of curving parcel trajectories is included in the force balance however a variety of density profiles is possible within the hot spot depending on the radius of curvature of the winds the most plausible profile implies that the hot spot is nearly dry adiabatic and that the equatorial zone south of the probe site is stable from 2 to 6 bars suggesting moist adiabatic upwellings with a water abundance of 1 2 times solar this is consistent with galileo and voyager images suggesting upwelling at the equator the profile further implies that from 1 to 5 bars the hot spot is denser than the equatorial zone south of the probe site third probe data indicate that nh 3 increased with depth below 1 bar and became constant by 8 bars h 2s began increasing below 8 bars and leveled off by 16 bars while water only began increasing below 12 bars and was still increasing with depth at 20 bars we propose that lateral mixing along isopycnals surfaces of constant potential density could produce the observed pattern alternatively the downwelling might consist of column stretching so that the nh 3 nh 4sh and water lifting condensation levels were pushed to 8 16 and 20 bars respectively in either case the simplest form of this model requires the downdraft to be less dense than the surroundings from 0 5 to 20 bars in its simplest form this model is therefore incompatible with our favored interpretation of the winds more detailed studies will be necessary to resolve the problem

peering through jupiter s clouds with radio spectral imaging radio wavelengths can probe altitudes in jupiter s atmosphere below its visible cloud layers we used the very large array to map this unexplored region down to 8 bar 100 kilometers below the visible clouds our maps reveal a dynamically active planet at pressures less than 2 to 3 bar a radio hot belt exists consisting of relatively transparent regions a low ammonia concentration nh3 being the dominant source of opacity probing depths to over 8 bar these regions probably coincide with 5 micrometer hot spots just to the south we distinguish an equatorial wave bringing up ammonia gas from jupiter s deep atmosphere this wave has been theorized to produce the 5 micrometer hot spots we observed the predicted radio counterpart of such hot spots

jupiter s unearthly jets a new turbulent model exhibiting statistical steadiness without large scale dissipation abstracta longstanding mystery about jupiter has been the straightness and steadiness of its weather layer jets quite unlike terrestrial strong jets with their characteristic unsteadiness and long wavelength meandering the problem is addressed in two steps the first is to take seriously the classic dowling ingersoll di 1 layer scenario and its supporting observational evidence pointing toward deep massive zonally symmetric zonal jets in the underlying dry convective layer the second is to improve the realism of the model stochastic forcing used to represent the effects of jupiter s moist convection as far as possible within the 1 layer dynamics of the di scenario the real moist convection should be strongest in the belts where the interface to the deep flow is highest and coldest and should generate cyclones as well as anticyclones with the anticyclones systematically stronger the new model forcing reflects these insights also it acts quasi frictionally on large scales to produce statisti

the earth s c21 and s21 gravity coefficients and the rotation of the core summary observational results for the earth s c21 and s21 gravity coefficients can be used to constrain the mean equatorial rotation of the core with respect to the mantle current satellite gravity solutions suggest the equatorial rotation rate is no larger than 1 x 10 7 times the earth s diurnal spin rate a limit more than one order of magnitude smaller than the polar rotation rate inferred from the westward drift of the earth s magnetic field the next generation gravity solutions should improve this constraint by more than one order of magnitude implications for the fluid pressure at the core mantle boundary and for the shape of that boundary are discussed

atmospheric electric potential gradient measurements of ash clouds generated by pyroclastic flows at unzen volcano japan atmospheric electric potential gradient measurements were made at two localities simultaneously during pyroclastic flow events on september 25 1993 at unzen volcano immediately after generation of the pyroclastic flows the potential gradients showed a positive anomaly that was followed by a negative anomaly the magnitude of the positive anomalies were nearly equal at the two measurement localities whereas the magnitude of the negative anomalies at the measurement locality close to the axis of the ash cloud was larger than the magnitude at the off axis measurement locality these differences may be accounted for by the differences in the distance between the ash cloud and each measurement locality it is suggested that the height to the positive charge was sufficiently larger and the height to the negative charge was sufficiently smaller than the horizontal distance between the two measurement localities our results suggest that the upper part of the ash cloud which contained volcanic gases and or relatively fine ash carried a net positive charge and the lower part of ash cloud which contained relatively coarse ash carried a net negative charge this charge distribution in the ash clouds generated by pyroclastic flows is more consistent with the results reported for vulcanian plumes from sakurajiama volcano lane and gilbert 1992 lane et al 1995 and asama volcano hatakeyama and ishikawa 1946 than any other cases

three dimensional velocity structure and resolution of the core mantle boundary region from whole mantle inversions of body waves the nature of the core mantle boundary cmb has important implications for deep earth processes particularly those which have their origin in the lower mantle or outer core the possibility of the existence of lateral p wave velocity variations in the outermost core is explored here by obtaining models of three dimensional cmb region velocity structure using an inversion of waveform data the numerical inversions involve determination of the three dimensional structure of the earth s outermost core and lower mantle using over 5000 long period seismic waveforms collected from global digital seismic networks spheroidal modes with periods between 33 and 100 s were selected to model the body wave portion of seismograms recorded from global earthquakes first order perturbations in s wave velocities in 11 mantle layers 200 350 km thick and p wave velocities in one outermost core layer comprise the least squares solutions to the inverse problem although the statistical f test supports the additional layer in the inversions this layer is not required by the f ratio to occur in the outermost core pattern retrieval resolution tests in which synthetic data constructed from an initial synthetic earth model are inverted for model parameters are used to compare parameters for one region to those of another in which some coefficient power smearing is suspected depth resolution tests indicate that the best radial resolution at the cmb is 500 km thus this method does not produce the resolution required for outermost core lateral velocity variation analysis an examination of the limitations of this approach demonstrates the need for waveform inversion techniques which more accurately predict raypaths in the deep mantle improvements in radial resolution are needed before whole mantle velocity models can begin to distinguish whether significant heterogeneity related to core mantle interactions occurs in the cmb region

steady flows at the top of earth s core derived from geomagnetic field models select models of the main geomagnetic field and its secular variation are extrapolated to the base of an insulating mantle and used to estimate the adjacent fluid motion of a perfectly conducting outer core the assumption of steady motion provides formally unique solutions and is tested along with that of no upwelling the hypothesis of no upwelling is found to be substantially worse than that of steady motion although the actual motion is not thought to be steady the large scale secular variation at the top of the core can be adequately described by a large scale combined toroidal poloidal circulation which is steady for intervals of at least a decade or two the derived flows include a bulk westward drift but are complicated by superimposed jets gyres and surface divergence indicative of vigorous vertical motion at depth the circulation pattern and key global properties including rms speed upwelling and westward drift are found to be fairly insensitive to variations in modeling parameters

a composite model of mesoscale convective complexes abstract a composite analysis technique is used to investigate the evolution of mesoscale features of mesoscale convective complexes mccs the early stage of the mcc lifecycle is characterized by convergence vertical motion and heating being centered in the lower troposphere as the mcc matures the level of peak upward motion and heating shifts to the upper troposphere the system achieves and maintains its maximum divergence upward motion and anticyclonic vorticity in the upper troposphere during the latter half of the life cycle this is in contrast to gate tropical clusters where the maximum divergence upward motion and anticyclonic vorticity occurred at the mature stage of the cluster and then weakened this difference might be explained by an mcc being an inertially stable form of mesoscale convective system whose radius exceeds the rossby radius of deformation the mcc is shown to be an efficient rain producer exhibiting a precipitation efficiency exceeding 100 at the mature stage due to th

core mantle interactions abstract recent studies of the magnetic field at the core mantle boundary have revealed fixed sites of either static magnetic features or persistent secular variation this suggests part of the magnetic field behaviour is controlled by the mantle the most plausible mechanism for core mantle interaction is thermal coupling although topography may also be significant the magnetic sites coincide with anomalies in lower mantle seismic velocity as determined from tomography and density as determined by flow models of mantle convection constrained by tomography and the geoid some magnetic features coincide with subduction zones particularly those near indonesia they may be caused by bumps on the core mantle boundary beneath trenches paleomagnetic pole positions suggest the magnetic behaviour has persisted for at least 5 myr as would be expected if it were controlled from the mantle

length of day variations caused by el nino southern oscillation and quasi biennial oscillation two prominent interannual atmospheric fluctuations the el nino southern oscillation in the troposphere ocean system and the quasi biennial oscillation in the equatorial stratosphere account for most of the observed interannual length of day lod variation from 1964 through 1987 with a relative contribution of about 2 to 1 thus the atmosphere lod connection extends from seasonal and shorter periods to interannual periods up to about 10 years

experimental investigation of volcanic particle aggregation in the absence of a liquid phase 1 understanding the dispersal and deposition of fine grained silicate particles from volcanic plumes is key to interpreting ash fall deposits and predicting hazards for future eruptions it is known that many of these particles fall incorporated into delicate dry aggregates whose sedimentation characteristics have not been previously investigated here we present the results of laboratory experiments on aggregates of small dry silicate particles produced by the fragmentation of pumice collected from the 18 may 1980 mount st helens fall deposit the aggregation process is driven by electrostatic charges naturally imparted to the particles during the fracture process for particle fall distances of 1 m images of the in flight aggregates show that they commonly have irregular shapes and are up to 800 m in size strobe photography was used to determine aggregate fall velocities and by representing aggregates as falling spheres suggested that they had densities of 100 200 kg m 3 comparable densities were obtained from experiments where equivalent fall velocities were assumed for aggregates and single particles which had been transported similar distances within a horizontal airflow these dispersal experiments produced bimodal particle size distributions similar to those observed in the 18 may 1980 mount st helens deposits and suggest that the aggregates were composed mainly of particles 70 m in diameter our experimental results are in agreement with aggregate size and density estimates previously used within several theoretical plume sedimentation models in order to explain some features of natural ash deposits

jupiter s cloud structure from galileo imaging data the vertical structure of aerosols on jupiter is inferred from data obtained by the nasa galileo solid state imaging system during the first six orbits of the spacecraft images at 889 nm a strong methane band 727 nm a weaker methane band and 756 nm continuum taken at a variety of lighting and viewing angles are used the images are displayed and described in the companion paper by vasavada et al 1998 icarus 135 265 275 conservative scattering cloud particles with laterally uniform single scattering properties are assumed in the analysis and are shown to be consistent with the data at these wavelengths particles are bright and the darkest locations on jupiter correspond to the smallest optical thickness of aerosols optical depths and vertical positions of aerosol layers vary from place to place and are the retrieved quantities in the analysis only mid and low latitudes are sampled in this data set a stratospheric haze with an optical depth of roughly a tenth and an upper tropospheric haze with an optical depth of 2 to 6 exist over all regions both are consistent with previous conclusions based on data of lower spatial resolution e g west et al 1986 icarus 65 161 217 the new data show that these layers contain little lateral structure on scales smaller than the planetary jets on scales of the jets and ovals the top and bottom of the upper tropospheric haze vary in elevation the concentration of particles optical depth per pressure interval varies less than does the total optical depth near the base of the upper tropospheric haze is a third cloud component usually at pressure p 750 200 mb which is less than a scale height in geometric thickness its optical depth varies from zero to about 20 on regional scales and often varies by 50 on scales of a few tens of kilometers optical depth variations in this cloud are the principal cause of the features in jupiter s atmosphere seen at red and longer wavelengths it is probably composed of ammonia the expected nh 4sh cloud has not been identified in this work perhaps because it exists only at locations where it is concealed beneath higher clouds our retrievals also cannot rule out a pervasive deep haze without small scale structure finally in one region northwest of the great red spot a deeper cloud is identified parts of it lie at a pressure greater than four bars it is associated with a rapidly changing storm system with optical depth of several tens or more and a range of cloud heights between p 4 bars to p 400 mb it is probably composed of water

variability of the topographic core mantle torque calculated from core surface flow models abstract with the prospect of studying the relevance of the topographic core mantle coupling to the variations of the earth s rotation and also its applicability to constraining the core surface flow we investigate the variability of the topographic torque estimated by using core surface flow models accompanied by a uncertainty due to the non uniqueness problem in the flow inversion and b variance originating in that of geomagnetic secular variation models employed in the inversion various flow models and their variances are estimated by inverting prescribed geomagnetic models at the epoch 1980 the subsequent topographic torque is then calculated by using a core mantle boundary topography model obtained by seismic tomography the calculated axial and equatorial torques are found subject to the variability of order 1 0 19 and 1 0 20 nm respectively on which b is more effective than a the variability of the torque is attributed even to a and b of the large scale flows degrees 2 and 3 yet it still seems unlikely for the decadal polar motion with the observed amplitude to be excited exclusively by the equatorial topographic torque associated with any of reasonable core surface flow models it is also confirmed that with the topography model adopted here the axial topographic torque on a rigid annulus in the core coaxial with the earth s rotation axis associated with any of reasonable flow models is larger by two orders of magnitude than the plausible inertial torque on such cylinders this implies that any core surface flow model consistent with the topographic coupling does not exist unless the topography model is appropriately modified nevertheless the topographic coupling might provide not only a weak constraint for explaining the decadal lod variations but also the possibility to probe the core surface flow and the core dynamics

moist convection and the 2010 2011 revival of jupiter s south equatorial belt fletcher was supported by a royal society research fellowship at the university of leicester giles was supported by a royal society research grant at the university of oxford the uk authors acknowledge the support of the science and technology facilities council stfc a portion of this work was performed by orton and payne at the jet propulsion laboratory california institute of technology under a contract with nasa this research used the alice high performance computing facility at the university of leicester we are extremely grateful for the combined efforts of the numerous amateur observers including those listed in the figure captions for sharing their data and for the jupos software developed by grischa hahn and hans jorg mettig to reproject the visible light data this investigation was partially based on thermal infrared observations acquired at i the eso very large telescope paranal ut3 melipal observatory using directors discretionary time program id 286 c 5009 and regular service time program id 087 c 0024 ii the subaru telescope which is 27 operated by the national astronomical observatory of japan program id o11154 iii nasa s infrared telescope facility which is operated by the university of hawaii under contract nnh14ck55b with the national aeronautics and space administration program ids 2010b010 2011a010 2011b027 and iv observations obtained at the gemini observatory program ids gn 2010b dd 3 gs 2010b q 8 and gs 2011aq 11 which is operated by the association of universities for research in astronomy inc under a cooperative agreement with the nsf on behalf of the gemini partnership the national science foundation united states the national research council canada conicyt chile ministerio de ciencia tecnolog ia e innovacion productiva argentina and ministerio da ci encia tecnologia e inovac ao brazil we wish to recognise and acknowledge the very significant cultural role and reverence that the summit of mauna kea has always had within the indigenous hawaiian community we are most fortunate to have the opportunity to conduct observations from this mountain

thermal core mantle interactions maps of the magnetic field at the core mantle boundary for 1715 1980 reveal static features in the field and an absence of westward drift from much of the core mantle boundary the static features suggest that flow in the core is coupled to the mantle we examine different coupling mechanisms and predict lateral inhomogeneity at the core mantle boundary comparison with models of the lower mantle and core mantle boundary derived seismically and from the geoid is encouraging though their resolution is currently inadequate for a full comparison to be made with the much better resolved magnetic field

electric potential gradient changes during explosive activity at sakurajima volcano japan we report electric potential gradient measurements carried out at sakurajima volcano in japan during 1 explosions which generated ash plumes 2 steam explosions which produced plumes of condensing gases and 3 periods of ashfall and plume induced acid rainfall sequential positive and negative deviations occurred during explosions which generated ash plumes however no deflections from background were found during steam explosions during periods of ashfall negative electric potential gradients were observed while positive potential gradients occurred during fallout of plume induced acid rain from the same eruption these results suggest that a dipole arrangement of charge develops within plumes such that positive charges dominate in the volcanic gas rich top and negative charges in the following ash rich part of the plume the charge polarity may be reversed for other volcanoes hatakeyama and uchikawa 1952 we suggest that charge is generated by fracto emission donaldson et al 1988 processes probably during magma fragmentation within the vent rather than by frictional effects within the plume

charge structure in volcanic plumes a comparison of plume properties predicted by an integral plume model to observations of volcanic lightning during the 2010 eruption of eyjafjallajokull iceland observations of volcanic lightning made using a lightning mapping array during the 2010 eruption of eyjafjallajokull allow the trajectory and growth of the volcanic plume to be determined the lightning observations are compared with predictions of an integral model of volcanic plumes that includes descriptions of the interaction with wind and the effects of moisture we show that the trajectory predicted by the integral model closely matches the observational data and the model well describes the growth of the plume downwind of the vent analysis of the lightning signals reveals information on the dominant charge structure within the volcanic plume during the eyjafjallajokull eruption both monopole and dipole charge structures were observed in the plume by using the integral plume model we propose the varying charge structure is connected to the availability of condensed water and low temperatures at high altitudes in the plume suggesting ice formation may have contributed to the generation of a dipole charge structure via thunderstorm style ice based charging mechanisms though overall this charging mechanism is believed to have had only a weak influence on the production of lightning

experimental generation of volcanic lightning explosive volcanic eruptions are commonly associated with intense electrical activity and lightning direct measurement of the electric potential at the vent where the electric activity in the volcanic plume is first observed is severely impeded limiting progress in its investigation we have achieved volcanic lightning in the laboratory during rapid decompression experiments of gas particle mixtures under controlled conditions and recorded it using a high speed camera and two antennas we find that lightning is controlled by the dynamics of the particle laden jet and by the abundance of fine particles the relative movement of clusters of charged particles generates the electrical potential which is necessary for lightning the experimental generation of volcanic lightning suggests that rapid progress can now be expected in understanding electrical phenomena in volcanic plumes to implement lightning monitoring systems and the forecasting of volcanic ash emissions

models of the core mantle boundary and the travel times of internally reflected core phases topographic maps of the core mantle boundary cmb obtained by inverting different subsets of international seismological centre arrival time data involving either waves refracted through the boundary pkp or waves reflected from the topside pcp do not agree we report on the implications for models of cmb structure when data from bottomside reflections notably pkkp are included in the inversion travel time residuals with respect to a reference earth model prem of all core phases are positively biased but the mean residual is different for different phases and must be accounted for prior to inversion the new data illustrate that models of cmb topography can explain only a small fraction of the data variance the new cmb model involves both topography and a laterally varying boundary layer the cmb itself is smooth compared to previous results

dynamical implications of jupiter s tropospheric ammonia abundance abstract groundbased radio observations indicate that jupiter s ammonia is globally depleted from 0 6 bars to at least 4 6 bars relative to the deep abundance of 3 times solar a fact that has so far defied explanation the observations also indicate that i the depletion is greater in belts than zones and ii the greatest depletion occurs within jupiter s local 5 m hot spots which have recently been detected at radio wavelengths here we first show that both the global depletion and its belt zone variation can be explained by a simple model for the interaction of moist convection with jupiter s cloud layer circulation if the global depletion is dynamical in origin then important endmember models for the belt zone circulation can be ruled out next we show that the radio observations of jupiter s 5 m hot spots imply that the equatorial wave inferred to cause hot spots induces vertical parcel oscillation of a factor of 2 in pressure near the 2 bar level which places important constraints on hot spot dynamics finally using spatially resolved radio maps we demonstrate that low latitude features exceeding 4000 km diameter such as the equatorial plumes and large vortices are also depleted in ammonia from 0 6 bars to at least 2 bars relative to the deep abundance of 3 times solar if any low latitude features exist that contain 3 times solar ammonia up to the 0 6 bar ammonia condensation level they must have diameters less than 4000 km

influence of viscoelastic coupling on the axial rotation of the earth and its fluid core summary linear equations governing the axial rotation of the earth are dcveloped for a model with a maxwell homogeneous mantle and a homogeneous inviscid fluid core having a differential rotation relative to the mantle we find three eigenfrequencies for the axial perturbations in rotation the first one is relative to friction acting at the core mantle boundary and the others are relaxation modes associated with viscoelastic love numbers we point out the differential rotation of the core when the earth is submitted to zonal geophysical excitations like glaciation and deglaciation tidal torque or other processes occurring at the core mantle boundary cmb we show that the tidal deceleration involves an eastward drift of the core with respect to the mantle however for precise values of the mantle viscosity and of the frictional constant at the cmb we find that the last deglaciation involves a westward drift of the core with respect to the mantle which may be correlated with the observed westward drift of the geomagnetic field of the earth

vertical cloud structure of jupiter s equitorial plumes abstract a model for the vertical cloud structure of jupiter s equitorial plumes is deduced based on an analysis of voyager images of the equitorial region in the 6190a methane band and the 6000 a continuum and ground based 8900 a methane band images of jupiter a computer code that represents scattering and absorption from aerosol and gas layers was applied to a heirarchy of increasingly complex model aerosol structures to match the observations in the three wavelengths the observations are consistent with a model for the vertical cloud structure of the equitorial region that consists of four aerosol layers a high altitude haze layer hal with optical depth 1 uniformly blankets the equitorial region at an altitude between 100 and 250 mbar below that a middle level cloud layer between 400 and 800 mbar contains the well known equatorial plumes the plume clouds are optically thick 12 bright clouds with single scattering albedo 0 997 they are probably composed of ammonia ice the darker 0 990 interplume regions contain optically thinner clouds 2 5 at the same altitude as the plumes an opaque cloud deck between 4000 and 6000 mbar which is probably composed of water forms the lowest model layer in addition to these three layers a thin forward scattering haze layer above 100 mbar was included in the models for consistency with previous work tomasko et al 1978 we conclude that the vertical structure of the equatorial plume clouds is consistent with the hypothesis hunt et al 1981 that the plumes are caused by upwelling at the ammonia condensation level produced by bouyancy due to latent heat release from the condensation of water clouds nearly three scale heights below the plumes

atmospheric waves and dynamics beneath jupiter s clouds from radio wavelength observations abstract we observed jupiter at wavelengths near 2 cm with the karl g jansky very large array vla in february 2015 these frequencies are mostly sensitive to variations in ammonia abundance and probe between 0 5 2 0 bars of pressure in jupiter s atmosphere within and below the visible cloud deck which has its base near 0 7 bars the resultant observed data were projected into a cylindrical map of the planet with spatial resolution of 1500 km at the equator we have examined the data for atmospheric waves and observed a prominent bright belt of radio hotspot features near 10 n likely connected to the same equatorial wave associated with the 5 m hotspots we conducted a passive tracer power spectral wave analysis for the entire map and latitude regions corresponding to eastward and westward jets and compare our results to previous studies the power spectra analysis revealed that the atmosphere sampled in our observation excluding the neb region is in a 2 d turbulent regime and its dynamics are predominately governed by the shallow water equations the great red spot grs is also very prominent and has a noticeable meridional asymmetry and we compare it and nearby storms with optical images we find that the meridional radio profile has a global north south hemisphere distinction and find correlations of it to optical intensity banding and to shear zones of the zonal wind profile over select regions of latitude amateur optical images taken before and after our observation complemented the radio wavelength map to investigate dynamics of the equatorial region in jupiter s atmosphere we find that two radio hotspots at 2 cm are well correlated with optical plumes in the neb additionally revealing they are not the same 5 m hotspot features correlated with optical dark patches between adjacent plumes this analysis exploits the vla s upgraded sensitivity and explores the opportunities now possible when studying gas giants especially atmospheric dynamics of layers beneath upper level clouds

analysis of magnetic data over part of the younger granite province of nigeria the results of a magnetic study of part of the younger granite province of nigeria are presented here spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources average magnetic source depth of 286 m has been obtained for the area and this is thought to be related to the depth to the top of the main anomalous structures in the area observed magnetic anomaly profiels taken across the area have been interpreted in terms of arbitrarily shaped bodies whose existence was confirmed by 3 d hilbert transformation using nonlinear optimization techniques the modelled bodies occur at depths of 200 760 m and have magnetizations of 0 29 0 47 a m the results from the analysis of the magnetic field are discussed in relation to the results from previous gravity studies over the area and the mode of emplacement of the younger granites