statistics of geomagnetic storms and ionospheric storms at low and mid latitudes in two solar cycles 1 the statistics of occurrence of the geomagnetic storms and ionospheric storms at kokubunji 35 7 n 139 5 e 26 8 n magnetic latitude in japan and boulder 40 0 n 254 7 e 47 4 n in america are presented using the dst and peak electron density nmax data in 1985 2005 covering two solar cycles 22 23 when 584 geomagnetic storms dst 50 nt occurred in addition to the known solar cycle and seasonal dependence of the storms the statistics reveal some new aspects 1 the geomagnetic storms show a preference for main phase mp onset at around ut midnight especially for major storms dst 100 nt over 100 excess mp onsets at ut midnight compared to a uniform distribution 2 the number of positive ionospheric storms at kokubunji about 250 is more than double that at boulder and 3 the occurrence of the positive storms at both stations shows a preference for the morning noon onset of the geomagnetic storms as expected from a physical mechanism of the positive storms 4 the occurrence of negative ionospheric storms at both stations follows the solar cycle phases most frequent at solar maximum better than the occurrence of positive storms which agrees with the mechanism of the negative storms

storm time electric fields in the equatorial ionosphere observed near the dusk meridian 1 we compare the dynamics of plasma drifts vp and ionospheric electric fields ei measured near the dusk meridian at the magnetic equator by the defense meteorological satellite program dmsp f13 satellite with those of the dawn to dusk component of the interplanetary electric field ief ey during four large magnetic storms presented data indicate that during the main phase of the magnetic storms when the interplanetary magnetic field imf had a southward component vp had upward and westward components that ranged up to 120 and 210 m s 1 the corresponding eastward and upward components of ei were approximately 5 and 10 of ey the persistence of eastward ei for many hours indicates that electric field shielding of the inner magnetosphere is ineffective during prolonged periods of southward imf during periods of northward imf ey 0 ionospheric responses depended on prior history no ionospheric response is apparent after strong northward imf turnings preceded by geomagnetic quiet if they occurred after a long southward interval ei often had westward and downward components the polarity of the zonal component of ei remained well correlated with that of ey for up to 21 h during periods of slowly varying imf phenomena associated with southward imf periods are consistent with models that allow for prolonged penetration electric field from high latitudes superposed on those of the sq current system however it is not understood why the remarkable correspondence between the polarities of the zonal component of ei and the ief ey occurs during northward imf in some ey 0 periods the vertical component of ei remained upward dmsp detections of upward ei westward vp during periods of ey 0 are not predicted by existing models

is a pyrolitic adiabatic mantle compatible with seismic data in this paper the simplest average physical model of a mantle convecting as a whole i e following an adiabatic temperature gradient with a single composition pyrolite with phase transitions is tested directly against global seismic data instead of against spherically symmetric seismic models constraints from seismic data on average velocities and lower mantle velocity gradients are hard to reconcile with an adiabatic pyrolitic mantle given the current state of knowledge of elastic and anelastic mineral parameters at high pressure and temperature this physical model generally gives a a stronger baseline offset between upper and lower mantle average travel time residuals than allowed by the data and b an insufficient decrease in velocity with depth in the lower mantle above 2500 km we tested 105 upper and 105 lower mantle models that were selected randomly within the mineral parameter uncertainties only 2 lower mantle models and 24 upper mantle models yield whole mantle seismic structures that are compatible with global isc p and s travel times and central frequencies of toroidal and spheroidal fundamental modes with angular order higher than 18 to improve the fit to the seismic data the physical model would require a a lower velocity transition zone composition than dry pyrolite at least around continents and subduction zones as well as b a gradual change in physical state of the lower mantle that decreases the velocity depth gradient e g a superadiabatic temperature gradient

sound velocities of majorite garnet and the composition of the mantle transition region the composition of the mantle transition region characterized by anomalous seismic wave velocity and density changes at depths of approximately 400 to 700 km has remained controversial some have proposed that the mantle transition region has an olivine rich pyrolite composition whereas others have inferred that it is characterized by pyroxene and garnet rich compositions piclogite because the sound velocities in pyrolite estimated from laboratory data are substantially higher than those seismologically observed although the velocities of the olivine polymorphs at these pressures wadsleyite and ringwoodite have been well documented those of majorite another significant high pressure phase in the mantle transition region with realistic mantle compositions have never been measured here we use combined in situ x ray and ultrasonic measurements under the pressure and temperature conditions of the mantle transition region to show that majorite in a pyrolite composition has sound velocities substantially lower than those of earlier estimates owing to strong nonlinear decreases at high temperature particularly for shear wave velocity we found that pyrolite yields seismic velocities more consistent with typical seismological models than those of piclogite in the upper to middle parts of the region except for the potentially larger velocity jumps in pyrolite relative to those observed at a depth of 410 km in contrast both of these compositions lead to significantly low shear wave velocities in the lower part of the region suggesting possible subadiabatic temperatures or the existence of a layer of harzburgite rich material supplied by the subducted slabs stagnant at these depths

on mantle chemical and thermal heterogeneities and anisotropy as mapped by inversion of global surface wave data 1 we invert global observations of fundamental and higher order love and rayleigh surface wave dispersion data jointly at selected locations for 1 d radial profiles of earth s mantle composition thermal state and anisotropic structure using a stochastic sampling algorithm considering mantle compositions as equilibrium assemblages of basalt and harzburgite we employ a self consistent thermodynamic method to compute their phase equilibria and bulk physical properties p s wave velocity and density combining these with locally varying anisotropy profiles we determine anisotropic p and s wave velocities to calculate dispersion curves for comparison with observations models fitting data within uncertainties provide us with a range of profiles of composition temperature and anisotropy this methodology presents an important complement to conventional seismic tomography methods our results indicate radial and lateral gradients in basalt fraction with basalt depletion in the upper and enrichment of the upper part of the lower mantle in agreement with results from geodynamical calculations melting processes at mid ocean ridges and subduction of chemically stratified lithosphere compared with preliminary reference earth model prem and seismic tomography models our velocity models are generally faster in the upper transition zone tz and slower in the lower tz implying a steeper velocity gradient while less dense than prem density gradients in the tz are also steeper mantle geotherms are generally adiabatic in the tz whereas in the upper part of the lower mantle stronger lateral variations are observed the retrieved anisotropy structure agrees with previous studies indicating positive as well as laterally varying upper mantle anisotropy while there is little evidence for anisotropy in and below the tz

a numerical study of nighttime ionospheric variations in the american sector during 28 29 october 2003 variations of nighttime f2 peak height hmf2 over the american sector during the 28 29 october 2003 storm period were investigated using the national center for atmospheric research thermosphere ionosphere electrodynamics global circulation model the model was generally able to reproduce the ionospheric variations on 28 29 october 2003 observed by the ionosondes a series of controlled model simulations were subsequently undertaken to examine the effects of electric fields and neutral winds on the ionosphere the numerical experiments suggest that the dramatic nighttime increase of hmf2 on the storm day 29 october is mainly caused by traveling atmospheric disturbances tads from the high latitudes of the northern hemisphere however the electric field plays an important role in causing the elevation of hmf2 in the equatorial region the prompt penetration electric field ppef associated with the southward component of the interplanetary magnetic field bz is westward on the nightside whereas when bz reverses and becomes northward the ppef is westward in the premidnight and turns to eastward in the postmidnight these ppefs greatly affect the low latitude ionosphere during storm time on 28 october even though the bz disturbance was weak with a short duration of southward bz the tads from the southern hemisphere can propagate to the northern hemisphere and result in the corresponding oscillations in the nightside hmf2

first observational evidence for opposite zonal electric fields in equatorial e and f region altitudes during a geomagnetic storm period 1 the strong westward electrojet and simultaneous upward drift of the equatorial ionospheric peak observed over south east asia and indian equatorial regions during the prolonged dst minimum phase of an intense geomagnetic storm during 14 15 december 2006 are investigated for the altitudinal variation of zonal electric field polarity using ground based and space borne observations the results show first observational evidence for simultaneous existence of daytime westward and eastward zonal electric fields at equatorial e and f region altitudes respectively in a wide longitude sector while the westward electric fields at e region altitudes cause westward electrojet at the same time the eastward zonal electric fields atfregion altitudes cause the upward drift of the equatorial ionospheric peak and reinforcement of the equatorial ionization anomaly eia even in the topside ionosphere 660 km the reversal of the electric fields is found to occur at 280 km height a clear bifurcation of f region plasma at 280 km is evident in the iso electron density contours due to these oppositely polarized zonal electric fields which manifests as an unusually deep cusp between f1 and f2 layers on equatorial ionograms

thermal structure of the shallow upper mantle beneath italy and neighbouring areas correlation with magmatic activity and geodynamic significance article using an advanced seismic velocity temperature conversion technique we infer the temperature and melt dis tribution in the upper mantle down to 300 km beneath italy and surroundings starting from absolute s wave velocity models the presence of melt indicated by the seismic reconstruction of the mantle structure in the tyrrhenian sea area requires an extension of the standard conversion procedure to allow for a correction of seismic velocities for the effect of hydrous melt occurrence the thermal structure of the upper mantle along four sections crossing the tyrrhenian basin and the italian peninsula is investigated some characteristics of the obtained thermal structures and melt distributions are well delineated and in accordance with recent models of the evolution of the tyrrhenian sea area the negative thermal anomalies observed in all sections clearly delineate the subduction process of the adriatic plate beneath umbria calabria and the aeolian arc or the episode of post continental convergence beneath tuscany or the thermal effect of the remnant of the adriatic plate campania temperature values at moho seem to be generally correlated with surface heat flow determinations in the tyrrhenian sea area and surroundings although most sectors of the study area like tuscan tyrrhenian area apennines and adriatic trough have not yet reached the steady state thermal regime the thermal gradients evaluated in the adria foreland are high in comparison with those of the back arc area tyrrhenian sea and could be an effect of the eastward mantle flow beneath adria lithosphere or a result of the presence of low fraction of melts 1 wt which cannot rise in compressive regimes or both the melt fraction distribution obtained by the conversion procedure is approximately correlated with the age of the magmatism the highest abundance occurring in the southern tyrrhenian sea in accordance with widespread active volcanism in this area

equatorial and low latitude ionosphere thermosphere system response to the space weather event of august 2005 1 the response of the equatorial and low latitude ionosphere thermosphere system to the geomagnetic storm during 23 26 august 2005 is investigated the study is carried out using the vertical total electron content vtec measured by gps receivers along the 77 78 e longitude and the o n2 ratio obtained from the global ultraviolet imager instrument on board the timed satellite the equatorial ionization anomaly eia shows a poleward latitudinal expansion on 24 august probably associated with an eastward prompt penetration electric field the equatorial and low latitudes show an increase in vtec during the main phase of the storm on 24 august the prompt penetration eastward electric field along with an increase in the o n2 ratio could be responsible for this observed positive phase the vtec variations on 24 august also reveal the signature of a large scale acoustic gravity wave traveling atmospheric disturbance propagating with a horizontal velocity of 750 m s suppression of the eia is observed during the storm recovery phase on 25 august which probably is associated with the westward disturbance dynamo electric field and the equatorward expansion of the neutral composition changes o n2 depletion

seismic scattering at the top of the mantle transition zone abstract we document strong seismic scattering from around the top of the mantle transition zone in all available high resolution explosion seismic profiles from siberia and north america this seismic reflectivity from around the 410 km discontinuity indicates the presence of pronounced heterogeneity in the depth interval between 320 and 450 km in the earth s mantle we model the seismic observations by heterogeneity in the form of random seismic scatterers with typical scale lengths of kilometre size 10 40 km by 2 10 km in a 100 140 km thick depth interval the observed heterogeneity may be explained by changes in the depths to the spinel transformations caused by an unexpectedly high iron content at the top of the mantle transition zone the phase transformation of pyroxenes into the garnet mineral majorite probably also contributes to the reflectivity mainly below a depth of 400 km whereas we find it unlikely that the presence of water or partial melt is the main cause of the observed strong seismic reflectivity subducted oceanic slabs that equilibrated at the top of the transition zone may also contribute to the observed reflectivity if this is the main cause of the reflectivity a substantial amount of young oceanic lithosphere has been subducted under siberia and north america during their geologic evolution subducted slabs may have initiated metamorphic reactions in the original mantle rocks

sounding of the topside ionosphere plasmasphere based on gps measurements from champ initial results 1 beside the gps radio occultation measurements of the troposphere and ionosphere the champ satellite tracks presently up to 8 gps satellites simultaneously for navigation the received dual frequency gps signals provide valuable information on the ionization state of the topside ionosphere and plasmasphere this paper briefly describes a new developed model assisted technique to improve the three dimensional electron density estimation above the champ orbit from these gps measurements application of this assimilation algorithm provides a 2 d electron density slice of the ionosphere plasmasphere system within the champ orbit plane from the champ altitude up to gps orbit heights we estimate the accuracy of the gps tec calibration and perform a first validation by comparing the retrieved electron density of the ionosphere plasmasphere slice at champ altitude to simultaneous electron density measurements of the langmuir probe onboard champ

the 3d model of the plasmasphere coupled to the ionosphere pierrard and stegen 2008 has been coupled with the ionospheric iri model in addition to the electron number density the plasmaspheric model is also developed to include the temperature profiles of the different particles and ion composition at altitudes from 60 to 2000 km results of the model for the f region trough are compared with coincident observations of middle and top ionosphere by means of satellite tomography and radar measurements a good match between the model and observations supports the idea that the present model is useful for investigating physical mechanism involved in the plasmasphere ionosphere coupling and for acquiring information about the plasmaspheric behaviour based on ionospheric observations

comparisons of ionospheric electron density distributions reconstructed by gps computerized tomography backscatter ionograms and vertical ionograms global positioning system gps computerized ionosphere tomography cit and ionospheric sky wave ground backscatter radar are both capable of measuring the large scale two dimensional 2 d distributions of ionospheric electron density ied here we report the spatial and temporal electron density results obtained by gps cit and backscatter ionogram bsi inversion for three individual experiments both the gps cit and bsi inversion techniques demonstrate the capability and the consistency of reconstructing large scale ied distributions to validate the results electron density profiles obtained from gps cit and bsi inversion are quantitatively compared to the vertical ionosonde data which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings our study can improve current understanding of the capability and insufficiency of these two methods on the large scale ied reconstruction

multisatellite observations of an intensified equatorial ionization anomaly in relation to the northern sumatra earthquake of march 2005 here we report multisatellite observations of ionospheric disturbances in relation to the occurrence of the m8 7 northern sumatra earthquake of 28 march 2005 the demeter detection of electro magnetic emissions transmitted from earthquake regions and champ challenging minisatellite payload satellite data were investigated to find possible precursory and postevent phenomena it was found that eia equatorial ionization anomaly strength expressed in the apex height derived from the champ plasma density profile was intensified along the orbits whose longitudes were close to the epicenter within about a week before and after occurrence of the earthquake increases in electron and o density along the orbits close to the epicenter were also observed in the demeter measurements the normalized equatorial plasma density derived from the demeter measurements showed intensification about a week before and after the earthquake reaching maximum the day after the shock and afterward disappearing in addition similar behavior of the eia enhancements related to the m8 0 pisco earthquake of 15 august 2007 was observed surveys of space weather and geomagnetic activities excluded the possibility that these fluctuations were caused by changes in space weather or by a geomagnetic storm statistical analyses of the longitudinal variation revealed that the eia was enhanced in the west of the epicenter and reduced in the east of the epicenter and this fits the increased conductivity model based on these observations we proposed a revised view of seismo ionospheric coupling in the region of the geomagnetic equator to explain the eia features observed in this study

f2 region response to geomagnetic disturbances across indian latitudes o 1s dayglow emission the morphology of ionospheric storms has been investigated across equatorial and low latitudes of indian region the deviation in f 2 region characteristic parameters f o f 2 and hf along with modeled green line dayglow emission intensities is examined at equatorial station thiruvananthapuram 8 5 degrees n 76 8 degrees e 0 63 degrees s geomagnetic latitude and low latitude station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude during five geomagnetic storm events both positive and negative phases have been noticed in this study the positive storm phase over equatorial station is found to be more frequent while the drop in ionization in most of the cases was observed at low latitude station it is concluded that the reaction as seen at different ionospheric stations may be quite different during the same storm depending on both the geographic and geomagnetic coordinates of the station storm intensity and the storm onset time modulation in the f 2 layer critical frequency at low and equatorial stations during geomagnetic disturbance of 20 23 november 2003 was caused by the storm induced changes in o n 2 it is also found that international reference ionosphere 2012 model predicts the f 2 layer characteristic f o f 2 and hf parameters at both the low and equatorial stations during disturbed days quite reasonably a simulative approach in glow model developed by solomon is further used to estimate the changes in the volume emission rate of green line dayglow emission under quiet and strong geomagnetic conditions it is found that the o s 1 dayglow thermospheric emission peak responds to varying geomagnetic conditions

southern hemisphere ionosphere and plasmasphere response to the interplanetary shock event of 29 31 october 2003 1 we analyze the effects on the southern hemisphere ionosphere and plasmasphere due to the 29 31 october 2003 geomagnetic storms the so called series of halloween storms solar wind data from ace and ionospheric data from the gps global position system ground and leo low earth orbit receivers the topex poseidon altimeter the image fuv camera and the dmsp drift meter are used to understand the ionospheric dynamics as a function of the storm phase the detailed structure of the ionosphere has been obtained using tomographic reconstruction applied to data from both ground and space based gps receivers the tomographic approach using leo observations of signals received from gps satellites above the leo s horizon allows us to investigate the topside ionospheric and plasmaspheric density distribution in more detail than can be obtained using ground based gps receivers this is because with ground based receivers the higher topside ionosphere and plasmasphere contribute only a small fraction to the total electron content tec and so the measurements are dominated by the ionospheric structure at the f2 peak in contrast the australian leo satellite fedsat which has been used for this study orbits at 800 km altitude well above the f2 peak and hence the tec measured is primarily due to the upper topside ionosphere and plasmasphere this paper presents the tomographically reconstructed topside ionosphere and plasmasphere electron density distributions using leo observations the temporal and regional maps of tec and the image fuv data show that the storm that commenced on 29 october dramatically decreased the plasma density in the southern hemisphere middle and high latitudes the region remained depleted of plasma for more than 24 hours until 31 october when the second severe storm began topex poseidon data shows a daytime localized density enhancement occurred above the middle of the pacific ocean these results show large interhemispheric and longitudinally narrow storm time structure in the ionosphere and topside ionosphere plasmasphere

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600 800 km in the mantle abstract phase transformations in a representative oceanic crust composition morb have been studied at pressures up to 28 gpa at 1200 c and 1500 c using a multi anvil apparatus the assemblage of majorite casio 3 rich perovskite stishovite which is displayed by the morb composition at pressures above 20 gpa was found to transform further into an assemblage containing a new aluminous phase at pressures above 25 gpa this al phase has a complex composition and is also relatively sodium rich its x ray diffraction pattern is similar to that observed for mgal 2 o 4 calcium ferrite type and is tentatively indexed on the basis of an orthorhombic cell yielding a zero pressure density of 3 87 2 g cm 3 majorite garnet was found to remain as the most abundant phase at the highest pressure studied 28 gpa and does not appear likely to transform to perovskite until pressures exceed 29 30 gpa these results imply that the basaltic crust component of subducted oceanic lithosphere would be 0 1 0 2 g cm 3 less dense than surrounding mantle pyrolite between the depths of 660 800 km thereby confirming an earlier hypothesis of anderson moreover the underlying layer of harzburgite would be 0 05 g cm 3 less dense than pyrolite throughout most of this depth interval these buoyancy relationships contribute to a barrier which impedes and may sometimes prevent the entry of slabs into the lower mantle

storm enhanced plasma density and polar tongue of ionization development during the 15 may 2005 superstorm we investigate the ionosphere s global response to the 15 may 2005 superstorm in terms of storm evolution and ionospheric electrodynamics our aim is to study the global distribution of plasma and the resultant large scale ionospheric features including the equatorial ionization anomaly eia storm enhanced density sed and polar tongue of ionization toi we have combined multi instrument ionospheric data solar and terrestrial magnetic data and polar convection maps results reveal the prompt penetration of the interplanetary electric field to the polar region and then to the equator with a dusk to dawn polarity during the initial phase and with a dawn to dusk polarity during the main phase this drove during the initial phase a weak eastward equatorial electrojet eej in the american sector at nighttime and a weak westward eej in the indian australian sector at daytime during the main phase these eejs intensified and changed polarities sed and polar toi development was observed prior to and during the initial phase at evening premidnight hours over north america and during the main phase in the south at afternoon evening hours in the australian sector during the main phase and early in the recovery phase the eia sed structure was well formed in the asian longitude sector then polar toi development was absent in the north because of the long distance from the magnetic pole but was supported in the south because of the closeness of daytime cusp and magnetic pole thus the eia sed toi structure developed twice but each time in a different longitude sector and with different characteristics

super plasma fountain and equatorial ionization anomaly during penetration electric field 1 relative importance of diffusion electric field and neutral wind on equatorial plasma fountain and equatorial ionization anomaly eia during a strong daytime eastward prompt penetration electric field ppef event are evaluated using the sheffield university plasmasphere ionosphere model and the recorded ppef during the super geomagnetic storm of 9 november 2004 the fountain rapidly develops into a super fountain during the ppef event the super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces or stops the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss the eia crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the ppef event however the crests become stronger than normal only in the presence of an equatorward wind the results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during a daytime eastward ppef event the equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms

duskside enhancement of equatorial zonal electric field response to convection electric fields during the st patrick s day storm on 17 march 2015 the equatorial zonal electric field responses to prompt penetration of eastward convection electric fields ppef were compared at closely spaced longitudinal intervals at dusk to premidnight sectors during the intense geomagnetic storm of 17 march 2015 at dusk sector indian longitudes a rapid uplift of equatorial f layer to 550 km and development of intense equatorial plasma bubbles epbs were observed these epbs were found to extend up to 27 13 n and 25 98 s magnetic dip latitudes indicating their altitude development to 1670 km at apex in contrast at few degrees east in the premidnight sector thailand indonesian longitudes no significant height rise and or epb activity has been observed the eastward electric field perturbations due to ppef are greatly dominated at dusk sector despite the existence of background westward ionospheric disturbance dynamo idd fields whereas they were mostly counter balanced by the idd fields in the premidnight sector in situ observations from swarm a and swarm c and communication navigation outage forecasting system satellites detected a large plasma density depletion near indian equatorial region due to large electrodynamic uplift of f layer to higher than satellite altitudes further this large uplift is found to confine to a narrow longitudinal sector centered on sunset terminator this study brings out the significantly enhanced equatorial zonal electric field in response to ppef that is uniquely confined to dusk sector the responsible mechanisms are discussed in terms of unique electrodynamic conditions prevailing at dusk sector in the presence of convection electric fields associated with the onset of a substorm under southward interplanetary magnetic field bz

reply to comment by f masci and j n thomas on temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake

new aspects of thermospheric and ionospheric storms revealed by champ 1 the neutral mass density n and electron density ne at 400 km height measured by champ during nine intense geomagnetic storms bring out some new aspects of the thermospheric and ionospheric storms the thermospheric storms increase of n develop with the onset of the main phases mp of the geomagnetic storms and reach their peak phases before or by the end of the mps the ionospheric storms change of ne in general undergo an initial negative phase with the equatorial ionization anomaly eia crests shifting poleward before turning positive and the positive storms reach their peak strengths or phases centered at 25 30 magnetic latitudes in some 4 cases the positive storms develop without an initial negative phase and with the eia crests shifting equatorward in all cases the positive storms reach their peak phases before the end of the mps and turn to conventional negative storms by the end of the mps the observations agree with the different aspects of a physical mechanism of the positive storms the observations also reveal that the halloween storms of 30 october 2003 with a short mp without fluctuations produced the strongest positive ionospheric storms through impulsive response and there is strong equinoctial asymmetry in the ionosphere and thermosphere during geomagnetic storms

simulation of low latitude ionospheric response to 2015 st patrick s day super geomagnetic storm using ionosonde derived pre vertical drifts over indian region

the altitude extension of the mid latitude trough and its correlation with plasmapause position 1 tomographic imaging provides a powerful technique for obtaining images of the spatial distribution of ionospheric electron density in an altitude versus geographic latitude grid at a specified longitudinal sector the method which involves monitoring the total electron content tec of the ionosphere using signals transmitted from the global positioning system gps has the ability to reveal the detailed structure of the ionosphere including the mid latitude trough the tomographic reconstruction of ionospheric electron density structures are performed at different specific longitudinal sectors both in the northern and southern hemisphere at the same time the plasmapause position is estimated from image euv images and mapped onto tomographic images the simultaneous location of the altitude extension of the mid latitude trough and the plasmapause position are essentially co located

a three dimensional radially anisotropic model of shear velocity in the whole mantle summary we present a 3 d radially anisotropic s velocity model of the whole mantle saw642an obtained using a large three component surface and body waveform data set and an iterative inversion for structure and source parameters based on non linear asymptotic coupling theory nact the model is parametrized in level 4 spherical splines which have a spacing of 8 the model shows a link between mantle flow and anisotropy in a variety of depth ranges in the uppermost mantle we confirm observations of regions with vsh vsv starting at 80 km under oceanic regions and 200 km under stable continental lithosphere suggesting horizontal flow beneath the lithosphere we also observe a vsv vsh signature at 150 300 km depth beneath major ridge systems with amplitude correlated with spreading rate for fast spreading segments in the transition zone 400 700 km depth regions of subducted slab material are associated with vsv vsh while the ridge signal decreases whilethemid mantlehasloweramplitudeanisotropy vsv in the lowermost 300 km which appears to be a robust conclusion despite an error in our previous paper which has been corrected here the 3 d deviations from this signature are associated with the large scale low velocity superplumes underthecentralpacificandafrica suggestingthatvsh vsv isgeneratedinthepredominant horizontal flow of a mechanical boundary layer with a change in signature related to transition to upwelling at the superplumes

a case study of ionospheric storm effects during long lasting southward imf bz driven geomagnetic storm multiple instrumental observations including gps total electron content tec fof2 and hmf2 from ionosondes vertical ion drift measurements from communication navigation outage forecasting system magnetometer data and far ultraviolet airglow measured by thermosphere ionosphere mesosphere energetics and dynamics global ultraviolet imager timed guvi are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14 17 july 2012 geomagnetic storm event which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below 10 nt in the east asian australian sector latitudinal profile of tec variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly eia crest regions which were caused by the combined effects of disturbance dynamo electric fields ddef and equatorward neutral winds in the recovery phase strong inhibition of eia occurred and the summer crest of eia disappeared on 16 july due to the combined effects of intrusion of neutral composition disturbance zone as shown by the timed guvi o n2 measurements and long lasting daytime westward ddef inferred from the equatorial electrojet observations the transit time of ddef over the dip equator from westward to eastward is around 2200 lt in the american longitude the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase preceded by storm enhanced density plume in the initial phase in addition multiple short lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field imf bz in the recovery phase and were responsible for enhanced the eia and equatorial ionospheric uplift around sunset

lehmann discontinuity as the base of an anisotropic layer beneath continents long period surface wave r 1 g 1 body wave s ss sss and scs reverberation data have been inverted to obtain anisotropic structures along seismic corridors that sample australia and the western pacific these models support the proposal that the lehmann discontinuity beneath stable continents represents a transition from an anisotropic lithosphere to a more isotropic material in the lower part of the continental tectosphere

waveform tomography reveals channeled flow at the base of the oceanic asthenosphere understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists using full waveform seismic tomography we imaged a pattern of horizontally elongated bands of low shear velocity most prominent between 200 and 350 kilometers depth which extends below the well developed low velocity zone these quasi periodic fingerlike structures of wavelength 2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers below 400 kilometers depth velocity structure is organized into fewer undulating but vertically coherent low velocity plumelike features which appear rooted in the lower mantle this suggests the presence of a dynamic interplay between plate driven flow in the low velocity zone and active influx of low rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer

inferring the thermochemical structure of the upper mantle from seismic data summary we test a mineral physics model of the upper mantle against seismic observations the model is based on current knowledge of material properties at high temperatures and pressures in particular elastic properties are computed with a recent self consistent thermodynamic model based on a six oxides ncfmas system we focus on average structure between 250 and 800 km we invert normal modes eigenfrequencies and traveltimes to obtain best fitting average thermal structures for various compositional profiles the thermochemical structures are then used to predict long period waveforms ss precursors waveforms and radial profiles of attenuation these examples show the potential of our procedure to refine the interpretation combining different data sets we found that a mixture of morb and harzburgite with the morb component increasing with depth is able to reproduce well all the seismic data for realistic thermal structures if the proportions of morb with depth do not change unrealistic negative thermal gradients below 250 km would be necessary to explain the data equilibrium assemblages such as pyrolite cannot fit the seismic data the elastic velocities predicted by the reference mineral physics model tested are too low at the top of the lower mantle even for the fastest and most depleted composition that is harzburgite an increase in v p of 1 per cent and in vs of 2 per cent improves the data fit significantly and is required to find models that fit both traveltimes and normal modes indicating the need for further experimental measurements of these properties at the simultaneously elevated pressure temperature conditions of the lower mantle extending our procedure to other seismic and density data and interpreting the 3 d structure holds promise to further improve our knowledge of the thermochemical structure of the upper mantle in addition the same database of material properties can be used in dynamic models to test whether the thermochemical structure inferred from geophysical observations is consistent with the earth s evolution

reflectivity of the 410 km discontinuity from pp and ss precursors a number of studies have confirmed the global existence of a transition zone discontinuity at 410 km depth by aligning large numbers of long period seismograms on a surface reflection phase before stacking in particular ss and pp precursors from the 410 km discontinuity termed p410p and s410s have revealed long wavelength topography of this discontinuity here we extend these techniques to examine the reflection coefficient of the 410 km discontinuity using our measurements of p410p and s410s amplitudes we constrain the impedance contrasts across the 410 km discontinuity we also show lateral variations in the p wave impedance contrast at 410 km which is typically low under north america and china and higher beneath the north pacific the s wave impedance contrast shows less variability on the regional scale however analysis of p410p and s410s amplitudes over smaller areas by binning traces into spherical caps shows that the s wave reflection coefficient varies over much shorter scale lengths than that for p waves the different patterns of variation for p410p and s410s reflection amplitudes could be due to the presence of melt water or other chemical heterogeneities in the transition zone other factors such as temperature or mantle olivine content variations could also influence precursor amplitudes but they would be expected to lead to correlated variations and so they cannot explain all the variation that we observe

a climatology of middle and upper atmosphere radar observations of thermospheric winds shigaraki middle and upper atmosphere mu radar observations of horizontal thermospheric winds in the magnetic meridian plane over the period september 1986 to september 1996 are reported as climatological averages in the form of time of day variations for several combinations of seasonal and solar activity conditions and are compared with winds predicted by the horizontal wind model hwm and with winds measured at saint santin and millstone hill the dominant feature of the mu wind behavior is its mean diurnal variation of northward flow by day and southward flow by night with the nighttime wind smoothly approaching and receding from a midnight maximum while the daytime wind tends to show two peaks a strong one in the early daylight hours and a weak one in the afternoon evening hwm shows the same unimodal nighttime and bimodal daytime behavior but the hwm pattern is shifted about 2 hours later in time the amplitude of the diurnal harmonic decreases from 78 m s at solar minimum to 45 m s at solar maximum while hwm shows a corresponding increase from 53 to 62 m s the diurnal amplitude is remarkably stable with season but is superposed on a steady wind of 41 m s southward in summer 15 m s northward in winter and midway between these limits at the equinoxes hwm shows a symmetric pattern of 30 m s southward in summer and 30 m s northward in winter ion drag appears to be the main regulator of wind speed and the seasonal wind patterns have a profound effect on the seasonal behavior of the ionosphere

formation of polar ionospheric tongue of ionization during minor geomagnetic disturbed conditions previous investigations of ionospheric storm enhanced density sed and tongue of ionization toi focused mostly on the behavior of toi during intense geomagnetic storms little attention has been paid to the spatial and temporal variations of toi during weak to moderate geomagnetic disturbed conditions in this paper we investigate the source and development of toi during a moderate geomagnetic storm on 14 october 2012 multi instrumental observations including gps total electron content tec defense meteorological satellite program dmsp in situ measured total ion concentration and ion drift velocity superdarn measured polar ion convection patterns and electron density profiles from the poker flat incoherent scatter radar pfisr have been utilized in the current analysis gps tec maps show salient toi structures persisting for about 5 h over high latitudes of north america on 14 october 2012 in the later recovery phase of the storm when the magnitudes of imf by and bz were less than 5 nt the pfisr electron density profiles indicate that the extra ionization for tec enhancements mainly occurred in the topside ionosphere with no obvious changes in the bottomside ionosphere and vertical plasma drifts additionally there were no signatures of penetration electric fields in the equatorial electrojet data and upward ion drifts at high latitudes at the same time strong subauroral polarization streams with ion drift speeds exceeding 2 5 km s carried sunward fluxes and migrated toward lower latitudes for about 5 based on the dmsp cross track drift measurements based on those measurements we postulate that the combined effects of initial build up of ionization at midlatitudes through daytime production of ionization and equatorward or less poleward than normal daytime neutral wind reducing downward diffusion along the inclined filed lines and an expanded polar ion convection pattern and its associated horizontal plasma transport are important in the formation of the toi

uncertainty of mantle geophysical properties computed from phase equilibrium models phase equilibrium models are used routinely to predict geophysically relevant mantle properties a limitation of this approach is that nonlinearity of the phase equilibrium problem precludes direct assessment of the resultant uncertainties to overcome this obstacle we stochastically assess uncertainties along self consistent mantle adiabats for pyrolitic and basaltic bulk compositions to 2000 km depth the dominant components of the uncertainty are the identity composition and elastic properties of the minerals for p wave speed and density the latter components vary little whereas the first is confined to the upper mantle consequently p wave speeds densities and adiabatic temperatures and pressures predicted by phase equilibrium models are more uncertain in the upper mantle than in the lower mantle in contrast uncertainties in s wave speeds are dominated by the uncertainty in shear moduli and are approximately constant throughout the model depth range

local time dependent response of postsunset esf during geomagnetic storms 1 development or inhibition of esf during magnetically active periods has been an important space weather topic of interest during the recent past in view of its applications in the satellite based navigational systems particularly the postsunset period exhibits significant variability for storm time development of esf versus longitude in this paper we report the results of a multi instrumental ground based and space borne and multistation study on the development inhibition of postsunset esf during five moderate to intense geomagnetic storms occurred during the low and descending phase of the solar activity period 2004 2006 it has been observed that the prompt penetration of eastward electric fields into low latitudes and subsequent development of esf occurred in all longitudinal sectors where the local time corresponds to postsunset hours during the entire main phase of the storm in this paper we show the development of plasma bubble irregularities over a wide longitudinal extent of 92 owing to the dusk time penetration of eastward electric fields into low latitudes either the sudden increase in ae index and or a marked decrease in sym h index may be used as proxies to determine the occurrence as well as the time of penetration of electric fields into equatorial and low latitudes however in such cases where the ae index does not represent any sudden increase the dsymh dt seems to be the better index to determine the time of penetration in this paper is also presented an interesting case where the prompt penetration eastward electric fields dominated the existing strong westward electric fields and subsequently caused the onset of spread f and scintillations at both vhf 244 mhz as well as l band 1 5 ghz frequencies

global ionospheric response to the 2009 sudden stratospheric warming event using ionospheric data assimilation four dimensional ida4d algorithm a data assimilation algorithm is used to delineate the time dependent three dimensional ionospheric response to the 2009 sudden stratospheric warming ssw event we use the ionospheric data assimilation four dimensional ida4d algorithm to study the global ionospheric response to the 2009 ssw this is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere ionosphere coupling via tidal modifications during the 2009 ssw event model results reveal that the dominant mode of ionospheric variability during the 2009 ssw is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1 the ida4d results completely characterize the tidal perturbation during the 2009 ssw for the first time and show the global 3 d structure of the tide in total electron content tec and electron density the largest ionospheric responses were seen at low latitudes where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere the ionospheric response to the warming was characterized by an increase in tec in the morning early afternoon sector and a decrease during the late afternoon evening period the effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km the ida4d results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 ssw event we suggest that this could be a result of the equatorial fountain effect being further modified by the summer to winter meridional neutral winds

inferring upper mantle structure by full waveform tomography with the spectral element method summary mapping the elastic and anelastic structure of the earth s mantle is crucial for understanding the temperature composition and dynamics of our planet in the past quarter century global tomography based on ray theory and first order perturbation methods has imaged long wavelength elastic velocity heterogeneities of the earth s mantle however the approximate techniques upon which global tomographers have traditionally relied become inadequate when dealing with crustal structure as well as short wavelength or large amplitude mantle heterogeneity the spectral element method on the other hand permits accurate calculation of wave propagation through highly heterogeneous structures and is computationally economical when coupled with a normal mode solution and applied to a restricted region of the earth such as the upper mantle sem importantly sem allows a dramatic improvement in accounting for the effects of crustal structure here we develop and apply a new hybrid method of tomography which allows us to leverage the accuracy of sem to model fundamental and higher mode long period 60 s waveforms we then present the first global model of upper mantle velocity and radial anisotropy developed using sem our model semum confirms that the long wavelength mantle structure imaged using approximate semi analytic techniques is robust and representative of the earth s true structure furthermore it reveals structures in the upper mantle that were not clearly seen in previous global tomographic models we show that semum favourably compares to and rivals the resolving power of continental scale studies this new hybrid approach to tomography can be applied to a larger and higher frequency data set in order to gain new insights into the structure of the lower mantle and more robustly map seismic structure at the regional and smaller scales

quantifying the relationship between short wavelength dynamic topography and thermomechanical structure of the upper mantle using calibrated parameterization of anelasticity oceanic residual depth varies on 5000 km wavelengths with amplitudes of 1 km a component of this short wavelength signal is dynamic topography caused by convective flow in the upper 300 km of the mantle it exerts a significant influence on landscape evolution and sea level change but its contribution is often excluded in geodynamic models of whole mantle flow using seismic tomography to resolve buoyancy anomalies in the oceanic upper mantle is complicated by the dominant influence of lithospheric cooling on velocity structure here we remove this cooling signal from global surface wave tomographic models revealing a correlation between positive residual depth and slow residual velocity anomalies at depths 300 km to investigate whether these anomalies are of sufficient amplitude to account for short wavelength residual depth variations we calibrate an experimentally derived parameterization of anelastic deformation at seismic frequencies to convert shear wave velocity into temperature density and diffusion creep viscosity asthenospheric temperature anomalies reach 150 c in the vicinity of major magmatic hotspots and correlate with geochemical and geophysical proxies for potential temperature along mid ocean ridges locally we find evidence for a 150 km thick low viscosity asthenospheric channel incorporating our revised density structure into models of whole mantle flow yields reasonable agreement with residual depth observations and suggests that 30 km deviations in local lithospheric thickness account for a quarter of total amplitudes these predictions remain compatible with geoid constraints and substantially improve the fit between power spectra of observed and predicted dynamic topography this improvement should enable more accurate reconstruction of the spatio temporal evolution of cenozoic dynamic topography

direct observational evidence for disturbance dynamo on the daytime low latitude ionosphere a case study based on the 28 june 2013 space weather event a case of the westward disturbance dynamo dd electric field influencing the daytime equatorial and low latitude ionosphere during a geomagnetic storm that occurred on 28 29 june 2013 is presented the gps total electron content tec observations from a network of stations in the indian equatorial low and middle latitude regions along with the radio beacon tec ionosonde and magnetic field observations are used to study the storm time behavior of the ionosphere negative ionospheric storm effects were seen over the low and middle latitudes during the storm time due to the presence of a westward dd electric field observations show that the suppression of the equatorial ionization anomaly eia from the morning hours itself on 29 june 2013 took place due to the prevailing westward dd electric field providing evidence for the model calculations by balan et al 2013 simulations using the gitm model also agree well with our results the present study gains importance as the direct observational evidences for disturbance dynamo effects on the daytime low latitude ionosphere and the eia are sparse as it has been difficult to delineate it from the compositional disturbances

ionospheric electron concentration imaging using combination of leo satellite data with ground based gps observations over china space based global positioning system gps data onboard low earth orbit satellites are used together with ground based gps observations to simultaneously image ionospheric electron density ied and it aims to improve the spatial resolution of ionospheric tomography high precision dual frequency gps data from the crustal movement observation network of china and several international gps service stations and the constellation observation system for meteorology ionosphere and climate cosmic are used to invert a time series of the ied profiles over china and surroundings some retrieved electron density profiles are compared with the results from cosmic occultation data processed by cosmic data analysis and archival center and the peak density in f2 nmf2 is verified by ionosonde data experimental results demonstrate the imaging effectiveness due to cosmic data used in the inversion and the potential benefits using cosmic data in such system are also discussed

equatorial ionospheric electric fields during the november 2004 magnetic storm 1 we use radar measurements from the jicamarca radio observatory magnetometer observations from the pacific sector and ionosonde data from brazil to study equatorial ionospheric electric fields during the november 2004 geomagnetic storm our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour indicative of undershielding and overshielding prompt penetration electric fields in the pacific equatorial region during the november 7 main phase of the storm when the southward imf the solar wind and reconnection electric fields and the polar cap potential drops had very large and nearly steady values this result is inconsistent with the recent suggestion that solar wind electric fields penetrate without attenuation into the equatorial ionosphere for several hours during storm main phase the largest daytime prompt penetration electric fields about 3 mv m ever observed over jicamarca occurred during the november 9 storm main phase when large equatorial electrojet current and drift perturbations were also present in the pacific and brazilian equatorial regions the rise and decay times of these equatorial electric fields were about 20 min longer than of the corresponding solar wind electric fields the ratios of prompt penetration electric fields and corresponding solar wind electric field changes were highly variable even during the day and had largest values near dawn also the prompt penetration electric fields did not show polar cap potential drop saturation effects our results clearly highlight that the relationships of prompt penetration and solar wind electric fields and polar cap potentials are far more complex than implied by simple proportionality factors

local time seasonal and solar cycle dependency of longitudinal variations of tec along the crest of eia over india 1 the global wave number 4 structure in the indian longitudinal region spanning from 70 to 95 e forming the upward slope of the peak in the total electron content tec are reported along the crest of equatorial ionization anomaly eia the continuous and simultaneous measurements from five gps stations of gps aided geo augmented navigation gagan network are used in this study the long term database 2004 2012 is utilized for examining the local time seasonal and solar cycle dependency on the longitudinal variations of tec our results confirm the existence of longitudinal variations of tec in accordance with wave number 4 longitudinal structure including its strength the results suggest that these variations in general start to develop at 09 lt achieve maximum strength at 12 15 lt and decay thereafter the decay rate depending on the season they are more pronounced in equinoctial season followed by summer and winter the longitudinal variations persist beyond midnight in equinox seasons whereas in winter they are conspicuously absent interestingly they also exhibit significant solar cycle dependence in the solstices whereas in the equinoxes they are independent of solar activity the comparison of crest to trough ratio ctr in the eastern 92 e and western 72 e extreme longitudes reveals higher ctr on the eastern side than over the western extreme suggesting the role of nonmigrating tides in modulating the exb vertical drift and the consequential eia crest formation

grain growth in synthetic marbles with added mica and water evolution of grain size in synthetic marbles was traced from compaction of unconsolidated powder through primary recrystallization and normal grain growth to a size stabilized by second phases to form the marbles reagent grade caco3 was mixed with 0 1 and 5 volume mica and heat treated under pressure with added water densification with negligible recrystallization occurred within one hour at 500 c and 500 mpa confining pressure primary recrystallization occurred at 500 550 c causing increases of grain size of factors of 2 5 resulting samples had uniform grain size gently curved grain boundaries and near equilibrium triple junctions they were used subsequently for normal grain growth studies normal grain growth occurred above 550 c at 800 c grain size d increased from 7 m d0 to 65 m in 24 hours growth rates fit the equation d n d 0 n kt where k is a constant and n 2 6 minor amounts of pores or mica particles inhibit normal grain growth and lead to a stabilized grain size dmax which depends on the size of the second phases and the inverse of their volume fraction raised to a power between 0 3 and 1 once dmax is reached normal growth continues only if second phases are mobile or coarsen or if new driving forces are introduced that cause unpinning of boundaries normal grain growth in solnhofen limestone was significantly slower than in pure synthetic marble suggesting that migration is also inhibited by second phases in the limestone

a study on ionospheric scintillation near the eia crest in relation to equatorial electrodynamics equatorial electrojet eej data which are considered as a proxy index of equatorial electric field are analyzed in conjunction with equatorial ionosonde total electron content tec and scintillation data near the equatorial ionization anomaly eia crest for the equinoctial months of high solar activity years 2011 2012 to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern eia crest only geomagnetically quiet and normal electrojet days are considered the diurnal profiles of eej on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks a series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of eej latitudinal profile of tec exhibits resurgence in eia structure around the postsunset period diurnal tec profile near the eia crest resembles postsunset secondary enhancement on the days with afternoon enhancement in eej occurrence of equatorial spread f and postsunset scintillation near the eia crest seems to follow the secondary enhancement events in eej both the magnitude and duration of enhanced eej are found to be important for postsunset intensification of eia structure and subsequent occurrence of equatorial irregularities a critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the eia crest the results are validated using archived data for the years 1989 1990 and explained in terms of modulation effects of enhanced equatorial fountain

an investigation of ionospheric responses and disturbance thermospheric winds during magnetic storms over south american sector 1 this paper presents the results of a study of the ionospheric and thermospheric response to magnetic storm disturbances for four stations covering a wide range of latitude in the south american region the study is based on the f layer critical frequency fof2 and the peak height hmf2 from fortaleza fz which is equatorial cachoeira paulista cp which is low latitude concepcion con a midlatitude site and king george island kgi a middle to high latitude site equivalent neutral winds are extracted from the measured hmf2 by employing the field line interhemispheric plasma flip model the equatorial ionization anomaly eia can undergo enhancement due to magnetospheric disturbance electric field that penetrates to low latitudes during the growth phase of a storm substorm whereas eia inhibition occurs more often under disturbance dynamo dd electric field season dependent meridional transequatorial winds can significantly alter the eia response to disturbance electric fields large amplitudes of dd electric field is observed during evening and morning hours in equinoctial but not in winter months over the brazilian low latitude of large westward magnetic declination angle large equatorward meridional wind surges seem to be helped by the presence of disturbance zonal westward winds the low latitude disturbance can in some cases be traced to specific disturbance fronts originating promptly from auroral activity enhancements this study confirms earlier studies that show that the quiet time meridional wind increases with increase of latitude and that over midlatitude it shows decreases with increase of solar flux due to the effect of the ion drag force this study further shows that the disturbance meridional wind and the intensity of dd electric field increase with increasing intensity of high latitude energy input the negative ionospheric storm phase over middle latitude observed in equinox and not in winter is also intensified with the increasing intensity of high latitude energy input

upper mantle discontinuity topography from thermal and chemical heterogeneity using high resolution stacks of precursors to the seismic phase ss we investigated seismic discontinuities associated with mineralogical phase changes approximately 410 and 660 kilometers km deep within earth beneath south america and the surrounding oceans detailed maps of phase boundary topography revealed deep 410 and 660 km discontinuities in the down dip direction of subduction inconsistent with purely isochemical olivine phase transformation in response to lowered temperatures mechanisms invoking chemical heterogeneity within the mantle transition zone were explored to explain this feature in some regions multiple reflections from the discontinuities were detected consistent with partial melt near 410 km depth and or additional phase changes near 660 km depth thus the origin of upper mantle heterogeneity has both chemical and thermal contributions and is associated with deeply rooted tectonic processes

new observational and experimental evidence for a plume fed asthenosphere boundary layer in mantle convection abstract the textbook view is that the asthenosphere is the place beneath the tectonic plates where competing temperature and pressure effects on mantle rheology result in the lowest viscosity region of earth s mantle we think the sub oceanic asthenosphere exists for a different reason that instead it is where rising plumes of hot mantle stall and spread out beneath the strong tectonic plates below this plume fed asthenosphere is a thermal and density inversion with cooler underlying average temperature mantle here we show several recent seismic studies that are consistent with a plume fed asthenosphere these include the seismic inferences that asthenosphere appears to resist being dragged down at subduction zones that a sub oceanic thermal inversion 250 350 km deep is needed to explain the seismic velocity gradient there for an isochemical mantle that a fast halo of shear wave travel times surrounds the hawaiian plume conduit and that an apparent seismic reflector is found 300 km beneath pacific seafloor near hawaii we also present 2d axisymmetric and 3d numerical experiments that demonstrate these effects in internally consistent models with a plume fed asthenosphere if confirmed the existence of a plume fed asthenosphere will change our understanding of the dynamics of mantle convection and melting and the links between surface plate motions and mantle convection

a physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 1 a physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi instrument observations theoretical modeling and basic principles according to the mechanism an equatorward neutral wind is required to produce positive ionospheric storms the mechanical effects of the wind 1 reduce or stop the downward diffusion of plasma along the geomagnetic field lines 2 raise the ionosphere to high altitudes of reduced chemical loss and hence 3 accumulate the plasma at altitudes near and above the ionospheric peak centered at around 30 magnetic latitudes daytime eastward prompt penetration electric field ppef if it occurs also shifts the equatorial ionization anomaly crests to higher than normal latitudes up to approximately 30 latitudes the positive ionospheric storms are most likely in the longitudes where the onset of the geomagnetic storms falls in the ionization production dominated morning noon local time sector when the plasma accumulation due to the mechanical effects of the wind largely exceeds the plasma loss due to the chemical effect of the wind the mechanism agrees with the multi instrument observations made during the supergeomagnetic storm of 7 8 november 2004 with 18 h long initial phase ip and 10 h long main phase mp the observations which are mainly in the japanese australian longitudes where the mp onset was in the morning 0600 lt 2100 ut show 1 strong positive ionospheric storms in ne nmax hmax global positioning system total electron content gps tec and 630 nm airglow intensity in both northern and southern hemispheres started at the morning 0600 lt mp onset and lasted for a day 2 repeated occurrence of strong eastward ppef events penetrated after the mp onset and superposed with westward electric field started before the mp onset and 3 storm time equatorward neutral winds inferred from 1 and 2 repeated occurrence of an unusually strong f3 layer with large density depletions around the equator was also observed during the morning noon mp

one dimensional physical reference models for the upper mantle and transition zone combining seismic and mineral physics constraints one dimensional seismic reference models are known to be a nonunique solution to global seismic data hampering an interpretation in terms of physical structure here we test the compatibility of the simplest hypothesis of a mantle convecting as a whole with a constant pyrolitic composition with phase transitions directly against the kind of seismic data that went into global seismic reference models focusing on upper mantle structure down to 800 km depth by randomly varying the elastic and anelastic parameters of the main mantle minerals within their uncertainty bounds we generate a set of 100 000 adiabatic pyrolitic models a small number of these models 0 1 give a fit to far regional p and s travel times reprocessed isc catalog u 18 5d 26d and fundamental spheroidal and toroidal modes reference earth model web page 1 60 that is as satisfactory as the fit of preliminary reference earth model prem or ak135 f although the accepted models have widely different combinations of the mineral parameters there is a preference for a relatively high olivine shear modulus and its pressure and temperature derivatives relatively low wadsleyite bulk and shear parameters and relatively high ringwoodite bulk modulus derivatives the resulting seismic profiles are very similar and compared to prem or ak135 have lower velocities above 400 km larger jumps near 410 lower transition zone gradients lower jumps around 660 and stronger gradients directly below such physical models that fit seismic data well enough to be useful as a seismic reference model can significantly facilitate physical interpretation of seismic structures

abnormal evening vertical plasma drift and effects on esf and eia over brazil south atlantic sector during the 30 october 2003 superstorm 1 equatorial f region vertical plasma drifts spread f and anomaly responses in the south american longitude sector during the superstorm of 30 october 2003 are analyzed using data from an array of instruments consisting of digisondes a vhf radar gps tec and scintillation receivers in brazil and a digisonde and a magnetometer in jicamarca peru prompt penetrating eastward electric field of abnormally large intensity drove the f layer plasma up at a velocity 1200 ms 1 during post dusk hours in the eastern sector over brazil the equatorial anomaly was intensified and expanded poleward while the development of spread f plasma bubble irregularities and gps signal scintillations were weaker than their quiet time intensity significantly weaker f region response over jicamarca presented a striking difference in the intensity of prompt penetration electric field between peru and eastern longitudes of brazil the enhanced post dusk sector vertical drift over brazil is attributed to electro dynamics effects arising energetic particle precipitation in the south atlantic magnetic anomaly sama these extraordinary results and their longitudinal differences are presented and discussed in this paper

longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics 1 accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time season and magnetic activity is required to improve the operation of space based navigation and communication systems the vertical density distribution especially at low and equatorial latitudes is governed by the equatorial electrodynamics that produces a vertical driving force the vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground based global positioning system gps total electron content tec similarly the vertical drift which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low midlatitude region can be estimated using ground magnetometer observations we present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes the east african and west south american sectors chains of gps stations in the east african and west south american longitudinal sectors covering the equatorial anomaly region of meridian 37 e and 290 e respectively are used to reconstruct the vertical density distribution similarly magnetometer sites of african meridian b field education and research amber and intermagnet for the east african sector and south american meridional b field array samba and low latitude ionospheric sensor network lisn are used to estimate the vertical drift velocity at two distinct longitudes the comparison between the reconstructed and jicamarca incoherent scatter radar isr measured density profiles shows excellent agreement demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes similarly the comparison between magnetometer estimated vertical drift and other independent drift observation such as from vefi onboard communication navigation outage forecasting system c nofs satellite and julia radar is equally promising the observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences especially the equatorial anomaly peaks expand to higher latitudes more in american sector than the african sector indicating that the vertical drift in the american sector is stronger than the african sector

seismic properties of anita bay dunite an exploratory study of the influence of water as a pilot study of the role of water in the attenuation of seismic waves in the earth s upper mantle we have performed a series of seismic frequency torsional forced oscillation experiments on a natural anita bay dunite containing accessory hydrous phases at high temperatures to 13008c and confining pressure pc o f 200 mpa within a gas medium high pressure apparatus both oven dried and pre fired specimens wrapped in ni fe foil within the poorly vented assembly were recovered essentially dry after 50 100 h of annealing at 13008c followed by slow staged cooling the results for those specimens indicate broadly similar absorptionband viscoelastic behaviour but with systematic differences in the frequency dependence of strain energy dissipation q 1 attributed to differences in the small volume fraction of silicate melt and its spatial distribution in contrast it has been demonstrated that a new assembly involving a welded pt capsule retains aqueous fluid during prolonged exposure to high temperaturescallowing the first high temperature torsional forced oscillation measurements under high aqueous fluid pore pressure pf at temperatures 410008c a marked reduction in shear modulus without concomitant increase in q 1 is attributed to the widespread wetting of grain boundaries resulting from grain scale hydrofracturing and the maintenance of conditions

geodynamic tomography constraining upper mantle deformation patterns from bayesian inversion of surface waves in the earth s upper mantle seismic anisotropy mainly originates from the crystallographic preferred orientation cpo of olivine due to mantle deformation large scale observation of anisotropy in surface wave tomography models provides unique constraints on present day mantle flow however surface waves are not sensitive to the 21 coefficients of the elastic tensor and therefore the complete anisotropic tensor cannot be resolved independently at every location this large number of parameters may be reduced by imposing spatial smoothness and symmetry constraints to the elastic tensor in this work we propose to regularize the tomographic problem by using constraints from geodynamic modelling to reduce the number of model parameters instead of inverting for seismic velocities we parametrize our inverse problem directly in terms of physical quantities governing mantle flow a temperature field and a temperature dependent viscosity the forward problem consists of three steps 1 calculation of mantle flow induced by thermal anomalies 2 calculation of the induced cpo and elastic properties using a micromechanical model and 3 computation of azimuthally varying surface wave dispersion curves we demonstrate how a fully nonlinear bayesian inversion of surface wave dispersion curves can retrieve the temperature and viscosity fields without having to explicitly parametrize the elastic tensor here we consider simple flow models generated by spherical temperature anomalies the results show that incorporating geodynamic constraints in surface wave inversion help to retrieve patterns of mantle deformation the solution to our inversion problem is an ensemble of models i e thermal structures representing a posterior probability therefore providing uncertainties for each model parameter

physical mechanism and statistics of occurrence of an additional layer in the equatorial ionosphere a physical mechanism and the location and latitudinal extent of an additional layer called the f3 layer that exists in the equatorial ionosphere are presented a statistical analysis of the occurrence of the layer recorded at the equatorial station fortaleza 4 s 38 w dip 9 s in brazil is also presented the f3 layer forms during the morning noon period in that equatorial region where the combined effect of the upward e b drift and neutral wind provides a vertically upward plasma drift velocity at altitudes near and above the f2 peak this velocity causes the f2 peak to drift upward and form the f3 layer while the normal f2 layer develops at lower altitudes through the usual photochemical and dynamical effects of the equatorial region the peak electron density of the f3 layer can exceed that of the f2 layer the f3 layer is predicted to be distinct on the summer side of the geomagnetic equator during periods of low solar activity and to become less distinct as the solar activity increases ionograms recorded at fortaleza in 1995 show the existence of an f3 layer on 49 of the days with the occurrence being most frequent 75 and distinct in summer as expected during summer the layer occurs earlier and lasts longer compared to the other seasons on the average the layer occurs at around 0930 lt and lasts for about 3 hours the altitude of the layer is also high in summer with the mean peak virtual height being about 570 km however the critical frequency of the layer f0f3 exceeds that of the f2 layer f0f2 by the largest amounts in winter and equinox f0f3 exceeds f0f2 by a yearly average of about 1 3 mhz

topside ionospheric irregularities as seen from multisatellite observations we use in situ data from champ and dmsp satellites along with data of gps receiver onboard champ satellite and ground based gps receivers to study the occurrence and global distribution of ionospheric irregularities during the main phase of the geomagnetic storm of 29 31 august 2004 minimum dst excursion of a128 nt using the champ gps measurements we created maps of gps phase fluctuation activity and found two specific zones of the most intense irregularities 1 the region of the auroral oval at high latitudes of both hemispheres and 2 the low latitudes equatorial region between africa and south america at high latitudes the topside ionospheric irregularities appeared to be more intensive in the southern hemisphere which is most likely due to seasonal variations in the interhemispheric field aligned currents system an analysis of multi instrumental observations reveals reinforcement of the equatorial ionization anomaly after sunset in atlantic sector on 30 august and formation of the significant plasma depletions and irregularities over a large longitudinal range equatorial irregularities were also found in the morning sector at the recovery phase of the storm in addition to low earth orbit leo gps measurements we analyze the leo in situ measurements and we show that these two techniques cannot be interchangeable in all cases because of the altitudinal extent of plasma irregularities overall we demonstrate that the leo gps technique can serve a useful tool for detection of the topside ionospheric irregularities during space weather events and may essentially contribute to other methods based on various instruments

new identification of deep moonquakes in the apollo lunar seismic data abstract a new computer search of the apollo lunar seismic data set for identification of deep moonquakes using a combination of waveform cross correlation and single link cluster analysis has increased the number of positively identified deep moonquakes by more than a factor of five from the previous 1360 to 7245 at least 88 new deep moonquake source regions nests have been discovered while some source regions previously identified as separate entities are now determined to be identical reducing the number of previously known source regions from 108 to 77 the newly identified deep moonquakes and their relationships to each other are likely to revise our understanding of their spatial and temporal distributions

storm time plasma transport at middle and high latitudes associated with the large scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions solar produced f region plasma is transported to and through the noontime cleft from a source region at middle and low latitudes in the afternoon sector as a result of the offset between the geomagnetic and geographic poles the afternoon sector region of strong sunward convection is shifted to increasingly lower geographic latitude throughout the interval between 12 ut and 24 ut a snowplow effect occurs in which the convection cell continually encounters fresh corotating ionospheric plasma along its equatorward edge producing a latitudinally narrow region of storm enhanced plasma density sed and increased total electron content which is advected toward higher latitudes in the noon sector the millstone hill incoherent scatter radar regularly observes sed as a spatially continuous large scale feature spanning local times between noon and midnight and at latitudes between the polar cap and its mid or low latitude source region for local times away from noon the latitude of most probable sed occurrence moves equatorward by 6 for an increase of 2 in the kp index during strong disturbances the topside sed is observed to be convecting sunward at 750 m s 1 with a flux of 1014 m 2 s 1 this feature accounts for the pronounced enhancement of ionospheric density near dusk at middle latitudes observed during the early stages of magnetic storms called the dusk effect and constitutes a source for the enhanced f region plasma observed in the polar cap during disturbed conditions

penetration of magnetospheric electric fields to the equator during a geomagnetic storm 1 penetration of the magnetospheric electric field to the equatorial ionosphere was examined for the geomagnetic storm on 6 november 2001 by analyzing the difference in magnitude of the geomagnetic storm recorded at the dayside geomagnetic equator yap 0 3 gml and low latitude okinawa 14 47 gml the penetrated electric field caused the dp2 currents at the equator i e eastward currents during the main phase of the storm while the overshielding currents i e westward currents dominated during the recovery phase it is shown that the ring current started to develop simultaneously with the onset of the equatorial dp2 within the temporal resolution of a few minutes these results imply prompt transmission of the dawn to dusk convection electric field to the inner magnetosphere as well as to the equatorial ionosphere it is found that the equatorial dp2 started to decrease one hour after the onset of the ring current development indicating shielding effects becoming effective at the equator during the latter half of the storm main phase the dp2 was then overwhelmed by the overshielding which resulted in the counter electrojet cej in the beginning of the storm recovery phase the image magnetometer chain data indicate that the westward auroral electrojet aej in the dawn sector was driven over midlatitude centered at 57 corrected geomagnetic latitude cgml during the main phase while the aej shifted rapidly poleward to the auroral latitude centered at 67 cgml in the beginning of the recovery phase the overshielding must be caused by the abrupt poleward shift of the rl facs as inferred from the poleward shift of the aej in addition to the decrease in their magnitude due to the decrease in magnitude of the southward imf the geomagnetic storm at the dayside geomagnetic equator was enhanced in amplitude with the ratio of 2 7 as compared with the geomagnetic storm at low latitude this amplification is a result of both effects of the dp2 currents and the cej associated with the main and recovery phases respectively it is suggested that the electric field associated with the dp2 currents contributed to the development of the ring current during the main phase while the overshielding electric field may contribute to cease developing the ring current during the recovery phase

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

ionospheric storm of early november 1993 in the indian equatorial region an investigation is made of the response of equatorial ionosphere in the indian 75 e sector to the major magnetic storm of november 3 1993 using data from the ionosonde and magnetometer networks spanning the region 0 3 34 5 n dip some outstanding and new aspects of the storm time ionospheric behaviour are revealed an anomalous and striking positive gradient in 0f2 from the magnetic equator to 34 5 dip developed under counter electrojet cej condition in the morning on november 4 corresponding to the early stage of the storm main phase this storm effect is attributed to plasma transport by a poleward surge in transequatorial winds due to large scale atmospheric gravity waves agws launched by auroral heating remarkable wave like variations in hpf2 and 0f2 immediately followed at locations away from dip equator till local sunset with concomitant disruptions in the development of the equatorial ionization anomaly eia rapid variations in meridional neutral winds due to large scale agws are assessed as the cause of the oscillations in hpf2 and the associated cyclic sequence of development and inhibition of eia as the outcome of the combined effects of plasma transport due to meridional winds and the plasma fountain driven by e b drift just after the onset of the storm recovery phase at 1800 lt a sudden and anomalous drop 54 57 in 0f2 prevailed throughout the anomaly region over the interval 1915 2330 lt with an apparent time delay in occurrence toward the magnetic equator this premidnight collapse of equatorial f region is interpreted in terms of horizontal transport of plasma across the equator toward the opposite hemisphere by an equatorward surge in meridional winds the case study showed that besides disturbances in the zonal electric field due to prompt penetration and ionospheric disturbance dynamo effects perturbations in neutral meridional winds played a prominent role in the ionospheric storm of november 4 1993 in the indian equatorial region

physical mechanisms of the ionospheric storms at equatorial and higher latitudes during the recovery phase of geomagnetic storms 1 the paper studies the physical mechanisms of the ionospheric storms at equatorial and higher latitudes which are generally opposite both during the main phase mp and recovery phase rp of geomagnetic storms the mechanisms are based on the natural tendency of physical systems to occupy minimum energy state which is most stable the paper first illustrates the recent developments in the understanding of the mechanisms during daytime mps when generally negative ionospheric storms in nmax and tec develop at equatorial latitudes and positive storms occur at higher latitudes including why the storms are severe only in some cases the paper then investigates the relative importance of the physical mechanisms of the positive ionospheric storms observed at equatorial latitudes within 15 during daytime rps when negative storms occur at higher latitudes using champ ne and gps tec data and sheffield university plasmasphere ionosphere model the results indicate that the mechanical effect of the storm time equatorward neutral winds that causes plasma convergence at equatorial f region could be a major source for the positive storms with the downwelling effect of the winds and zero or westward electric field if present acting as minor sources

shear velocity structure and mineralogy of the transition zone beneath the east pacific rise abstract models of seismic velocity as a function of depth through the upper mantle provide some of the strongest constraints on the mineralogy and composition of the mantle although receiver function studies have provided new information on the depths of upper mantle discontinuities they do not provide as much information on seismic gradients between discontinuities and absolute velocities within the upper mantle the waveforms and travel times of upper mantle turning waves provide the strongest constraints on vertical variations in upper mantle velocity although in the past they suffered from the lack of dense profiles of data sampling a single part of the upper mantle that would minimize effects of 3d variations in velocity here we model three dense profiles of triplicated upper mantle broadband s and ss waves recorded by usarray canadian and nars baja stations located in western north america earthquakes along the east pacific rise were recorded along profiles within 5 back azimuth windows and with stations at a maximum of 0 5 separation the distance range covered is from 35 to 60 and thus the waves sample the mantle from the shallow upper mantle to depths near 1000 km the data were inverted using a conjugate gradient algorithm that utilizes the reflectivity synthetic technique the results show a much smaller gradient within the transition zone than the prem model with larger jumps in velocity across the 410 km and 660 km depth discontinuities these results are consistent with velocities predicted for a pyrolite composition mantle transition zone compositional models with lower olivine content such as piclogite are not consistent with our seismic model

observations of the ionospheric response to the 15 december 2006 geomagnetic storm long duration positive storm effect 1 the long duration positive ionospheric storm effect that occurred on 15 december 2006 is investigated using a combination of ground based global positioning system gps total electron content tec topex and jason 1 tec and topside ionosphere plasmasphere tec gps radio occultation and tiny ionospheric photometer tip observations from the constellation observing system for meteorology ionosphere and climate cosmic satellites this multi instrument approach provides a unique view of the ionospheric positive storm effect by revealing the storm time response in different altitude regions the ground based gps tec topex jason 1 tec and topside ionosphere plasmasphere tec all reveal significant enhancements at low latitudes to midlatitudes over the pacific ocean region during the initial portions of the storm main phase from 0000 0400 universal time ut on 15 december at low latitudes the topside ionosphere plasmasphere tec increase represents greater than 50 of the tec enhancement that is observed by ground based gps receivers moreover electron density profiles obtained using the technique of gps radio occultation demonstrate that the f layer peak height increased by greater than 100 km during this time period the effects of soft particle precipitation are also apparent in the cosmic observations of topside ionosphere plasmasphere tec the positive storm effects over the pacific ocean region remain present in the equatorial ionization anomaly crest regions beyond 1200 ut on 15 december this long lasting positive storm effect is most apparent in ground based gps tec and cosmic tip observations while only a small increase in the topside ionosphere plasmasphere tec after 0400 ut is observed this indicates that the long lasting positive storm effect occurs predominantly at f region altitudes and furthermore that refilling of the topside ionosphere and plasmasphere is not the primary mechanism for producing the long lasting positive storm phase during this event the observations suggest that the enhanced eastward electric field and equatorward neutral wind are likely to play a significant role in the generation of long lasting positive storm effects

positive and negative ionospheric storms occurring during the 15 may 2005 geomagnetic superstorm this study focuses on the 15 may 2005 geomagnetic superstorm and aims to investigate the global variation of positive and negative storm phases and their development observations are provided by a series of global total electron content maps and multi instrument line plots coupled thermosphere ionosphere plasmasphere electrodynamics ctipe simulations are also employed results reveal some sunward streaming plumes of storm enhanced density sed over asia and a well developed midlatitude trough over north america forming isolated positive and negative storms respectively the simultaneous development of positive and negative storms over north america is also shown then some enhanced auroral ionizations maintained by strong equatorward neutral winds appeared in the depleted nighttime ionosphere meanwhile the northern nighttime polar region became significantly depleted as the sed plume plasma could not progress further than the dayside cusp oppositely a polar tongue of ionization toi developed in the daytime southern polar region according to ctip simulations solar heating locally maximized minimized over the southern northern magnetic pole furthermore strong upward surges of molecular rich air created o n decreases both in the auroral zone and in the trough region while some sed related downward surges produced o n increases from these results we conclude for the time period studied that 1 composition changes contributed to the formation of positive and negative storms 2 strengthening polar convection and increasing solar heating of the polar cap supported polar toi development and 3 a weaker polar convection and minimized solar heating of the polar cap aided the depletion of polar plasma