statistical characteristics of the day to day variability in the geomagnetic sq field 1 day to day variability in the geomagnetic sq field is studied by using the magnetic data from a meridian chain of magnetometers along 120 e longitude the method of natural orthogonal components noc or eigenmode analysis is applied to separate the sq variation from complicated disturbances the first eigenmode with the largest eigenvalue represents fairly well the sq variation with a conspicuous day to day variability in the daily range for the stations on the same north or south side of the sq current system focus the day to day variations show a positive correlation in contrast for the stations on the different sides of the sq focus they show a negative correlation suggesting an important role of latitudinal shift of the sq current system focus to the day to day variability in the sq daily range the sq daily range is correlated with the magnetic indices ap and dst in a peculiar way on some severe disturbed days noticeable enhancements of the sq are observed implying increases in the ionospheric conductivities and or tidal wind velocities on other severe disturbed days however dramatically reduced sq variations occur suggesting dominant effects of the disturbance dynamo process

petrology of the 1991 1995 eruption at unzen effusion pulsation and groundmass crystallization abstract effusive eruption of dacite magma 2 1 108 m3 during 1991 1995 formed a lava dome at the summit of unzen volcano japan the effusion rate was highest at the beginning 4 0 105 m3 day 4 6 m3 s and decreased roughly with time to almost zero before this pattern was repeated with a second pulse of magma supply the whole rock chemistry of lavas shows significant variation attributable to variations in phenocryst abundance the more mafic the more abundant the phenocrysts the pattern of chemical variation with time shows some difference from that of the effusion rate all phenocrysts in dacite plagioclase hornblende biotite quartz and magnetite show evidence of disequilibrium with melt although a glomerophyric aggregation of phenocrysts suggests coexistence with each other phenocrysts are isotopically heterogeneous from species to species the calculated initial melt composition was rhyodacite and was nearly constant throughout the activity in contrast the bulk phenocryst population is andesite a model explaining the textures and the isotopic heterogeneity is the capture of diorite fragments or xenocrysts by parental rhyodacite magma it is suggested that when effusion rate was high less viscous crystal poor magma exited from the reservoir groundmass glass and plagioclase microlite rims show temporal chemical variations correlating with the effusion rate the higher the effusion rate the more evolved the compositions groundmass crystallinity increased with decreasing effusion rate from 33 to 50 textures in dome lavas suggest that groundmass crystallization had been mostly completed when magma reached the conduit top the fe ti oxide temperature 880 780 c was low when the crystallinity was high micropumice erupted before dome growth provided a sample recording magmatic foam in the conduit porosity of dome lavas was lower at lower effusion rates collapse of foam magma and simultaneous escape of volatiles through the conduit top were probably responsible for the accompanying low frequency earthquakes phenocrysts were broken and the breakdown rims on hornblende phenocrysts were torn off during collapse and successive compaction when effusion waned degassing and the resultant crystallization proceeded more completely so that the magma became too viscous to flow in the conduit top and behaved as a plug resulting in a temporary halt of effusion in turn groundmass crystallization in magma below the plug increased excess pressure in the upper parts of conduit due to slow cooling the plug was scavenged when rising excess pressure overcame its effective strength then the second pulse of magma supply began strong endogenous growth and extrusion of a lava spine in the later stage probably occurred for the same reason

seismic and infrasonic signals associated with an unusual collapse event at the soufriere hills volcano montserrat 1 in march 2004 during a period of no magma extrusion at soufriere hills volcano montserrat an explosive event occurred with little precursory activity recorded broadband seismic signals ranged from an ultra long period signal with a dominant period of 120 s to impulsive short duration events containing frequencies up to 30 hz synthetic displacement functions were fit to the long period data after application of the seismometer response these indicate a shallow collapse of the volcanic edifice occurred initiated 300 m below the surface lasting 100 s infrasonic tremor and pulses were also recorded in the 1 20 hz range the high frequency seismicity and infrasound are interpreted as the subsequent collapse of a gravitationally unstable buttress of remnant dome material which impacted upon the edifice surface this unique dataset demonstrates the benefits of deploying multi parameter stations equipped with broadband instruments

a comprehensive model of the quiet time near earth magnetic field phase 3 summary the near earth magnetic field is caused by sources in the earth s core ionosphere magnetosphere lithosphere and from coupling currents between the ionosphere and the magnetosphere and between hemispheres traditionally the main field low degree internal field and magnetospheric field have been modelled simultaneously with fields from other sources being modelled separately such a scheme however can introduce spurious features especially when the spatial and temporal scales of the fields overlap a new model designated cm3 comprehensive model phase 3 is the third in a series of efforts to coestimate fields from all of these sources this model has been derived from quiet time magsat and pogo satellite and observatory hourly means measurements for the period 1960 1985 it represents a significant advance in the treatment of the aforementioned field sources over previous attempts and includes an accounting for main field influences on the magnetosphere main field and solar activity influences on the ionosphere seasonal influences on the coupling currents a priori characterization of the influence of the ionosphere and the magnetosphere on earth induced fields and an explicit parametrization and estimation of the lithospheric field the result is a model that describes well the 591 432 data with 16 594 parameters implying a data to parameter ratio of 36 which is larger than several popular field models

tropical oceanic cloudiness and the incidence of precipitation early results from cloudsat 1 results of analysis of cloudsat radar data collected during the first three months of operation are described it is shown that the global tropical oceans 30n 30s predominantly favor clouds with tops in two layers centered at about 2 and 12 km precipitating clouds occur primarily in three modes a shallow mode that is the most frequent type as well as a middle and deep mode regional features are also discussed the indian and western pacific oceans exhibit more predominantly high clouds and deeper precipitation features than the eastern pacific and atlantic the occurrence of a mid level mode of cloudiness and precipitation is shown to vary regionally being particularly significant in the western pacific for all regions examined precipitating clouds are observed to be deeper than non precipitating clouds over the global tropical oceans 18 of the clouds detected by cloudsat produce precipitation

local time stacking of geomagnetic solar daily variations 1 regular geomagnetic solar daily variations the sq signal is used in electromagnetic induction studies to investigate the electrical conductivity structure of earth s upper mantle traditionally sq induction studies employ observatory magnetic data from a few quiet days in which the overprint on the regular sq ionospheric current vortices from various irregular disturbances is minimal active days are typically discarded a procedure which results in a gappy time series that is difficult to analyze furthermore the quiet day selection is largely arbitrary since daily geomagnetic activity levels range continuously from very quiet to very active this fact precludes the establishment of rigorous quiet active thresholds the average local time variation on active days resembles typical quiet day variations except for a multiplicative scaling factor a multiyear stack of yearlong geomagnetic time series aligned with respect to local time incorporates regular active days while greatly attenuating the effects of irregular geomagnetic disturbances external and internal current systems that rise and fall in step with the sun s transit across the sky above an observatory contribute coherently to the local time stack all other current systems are incoherent and tend to stack out an exact 1 year long stack preserves the seasonal variation the resulting stacked time series contains no gaps is dominated by regular solar daily variations and can be used for improved sq induction studies and comprehensive geomagnetic field modeling hourly geomagnetic values from niemegk boulder mbour and meanook observatories between 1970 and 2002 along with the ap index are used in this study

on induction effects of geomagnetic daily variations from equatorial electrojet and solar quiet sources at low and middle latitudes 1 we investigate the spatiotemporal behavior of the magnetic vertical component z of the daily ionospheric current systems the equatorial electrojet eej and solar quiet sq variations considering induction in the mantle and oceans the inducing eej and sq current systems are provided by the comprehensive model of sabaka et al 2004 the three dimensional 3 d conductivity model of the earth includes oceans of laterally variable conductance and a spherical conductor 1 d underneath our model studies demonstrate that induction effects in z due to the eej are negligible everywhere inland for all local times at champ altitude 400 km the magnetic signal induced by eej above the oceans does not exceed 2 5 of the external field during local noon this in particular means that considering the induction effects is not necessary when modeling the eej current strength from inland surface magnetic measurements and or satellite data as expected induction in the oceans strongly affects the sq field the model studies show that the anomalous induction effect defined as the difference between results obtained with 1 d and 3 d conductivity models of sq is substantial at champ altitude comprising 50 of the total field it is therefore necessary to consider induction in the oceans when modeling sq variations for both ground based and satellite data finally we demonstrate that the anomalous behavior of the daily variations in z at south indian sites namely a large positive prenoon peak can be explained by 3 d induction of the sq variations with no contribution from the eej

gas mass derived by infrasound and uv cameras implications for mass flow rate abstract mass flow rate is one of the most crucial eruption source parameter used to define magnitude of eruption and to quantify the ash dispersal in the atmosphere however this parameter is in general difficult to be derived and no valid technique has been developed yet to measure it in real time with sufficient accuracy linear acoustics has been applied to infrasonic pressure waves generated by explosive eruptions to indirectly estimate the gas mass erupted and then the mass flow rate here we test on stromboli volcano italy the performance of such methodology by comparing the acoustic derived results with independent gas mass estimates obtained with uv cameras and constraining the acoustic source by thermal imagery we show that different acoustic methods give comparable total gas masses in the 2 to 1425 kg range which are fully consistent with the gas masses derived by uv cameras and previous direct so 2 measurements we show that total erupted gas mass estimated by infrasound is not simply a function of the initial pressure but rather the full infrasonic waveform should be considered thermal imagery provides evidence that infrasound is generated during the entire gas thrust phase we provide examples to show how total gas masses derived by infrasonic signals can be affected by large uncertainties if duration of the signal is neglected only when duration of infrasound is included the best correlation 0 8 with uv cameras and the 1 1 direct linear proportionality is obtained our results open new perspective for remotely derived gas mass and mass flow rates from acoustic signals

infrasound from volcanic rockfalls proximal infrasound arrays can robustly track rapidly moving gravity driven mass wasting which occurs commonly at erupting volcanoes this study reports on detection localization and quantification of frequent small rockfalls and infrequent pyroclastic density currents descending the southeast flanks of santiaguito s active caliente dome in january of 2014 such activities are identified as moving sources which descend several hundred meters at bulk flow speeds of up to 10 m s which is considerably slower than the descent velocity of individual blocks infrasound rockfall signal character is readily distinguishable from explosion infrasound which is manifested by a relatively fixed location source with lower frequency content in contrast the rockfalls of santiaguito possess higher frequencies dominated by 7 5 to 20 hz energy during our observation periods typical rockfall signals occurred 10 times per hour and lasted tens of seconds or more array beamforming permitted detection of rockfall transients with amplitudes of only a few tens of millipascals that would be impossible to distinguish from noise using a single sensor conjoint time synchronized video is used to corroborate location and to characterize various gravity driven events

spherical harmonic analysis of geomagnetic tides 1964 1965 the mathematical forms chosen for analyses of s q and l by seventeen different authors are reviewed on the basis of the review and on consideration of the ionospheric dynamo theory and the hough function structure of wind velocities in the upper atmosphere a mathematical model is chosen that includes two more terms than the recent analysis by malin 1973 hourly mean values from 130 magnetic observatories for the i q s ys international quiet solar years 1964 and 1965 were prepared in machine readable form and analysed the solar and lunar transient magnetic variations were evaluated together with the lunar elliptic magnetic tide and the seasonal change at one and two cycles per year for all magnetic tides spherical harmonic analyses were made of the phase law tides and the smaller partial tides altogether 94 different spherical harmonic analyses were completed for a total of ten different magnetic tides two of the ten tides are the solar and lunar magnetic tides usually denoted s and l respectively the results are tabulated in a form that distinguishes between eastward and westward moving terms which is suitable for the evaluation of phase angle differences and amplitude ratios between internal and external parts malin s ocean dynamo calculation has been applied to the lunar and lunar elliptic magnetic tides the spherical harmonic coefficients are compared in some detail with those of malin 1973 for years of high sunspot activity the magnetic tidal potential associated with a given atmospheric tidal mode is derived theoretically and used to obtain an estimate of the hough function components of the solar and lunar semi diurnal atmospheric tides at ionospheric levels from the corresponding magnetic tidal potential

contribution at satellite altitude of electromagnetically induced anomalies arising from a three dimensional heterogeneously conducting earth using sq as an inducing source field summary the induced magnetic signature at satellite altitude associated with crustal and mantle electrical heterogeneities is examined using five different earth models the three dimensional induction problem is solved in these models using the solar quiet daily variation as an inducing source field every model has an upper shell representing the land ocean electrical conductivity distribution the different models have either a homogeneous mantle or a heterogeneous mantle containing either subduction zones a ridge system or conductive blocks electromagnetic anomalies presented in the form of geographical maps are calculated for wavelengths related to spherical harmonics of degrees in the ranges 1 12 and 13 27 respectively magnetic anomalies are calculated at an altitude of 400 km and for three different local times 6 12 and 18 h

electromagnetic induction in a spherical earth with non uniform oceans and continents in electric contact with the underlying medium ii bimodal global geomagnetic sounding of the lithosphere summary the vertical electric currents flowing between the inhomogeneous surface layer and the conductive layers of the earth s mantle are substantially dependent upon the transverse resistivity of the earth s crust and upper mantle although these currents do not contribute straightforwardly to a surface magnetic field they change the vortex sub surface currents which contribute to it thus there exists an indirect influence of leakage currents upon the magnetic field this makes it possible to evaluate resistance of the high ohmic layers which could not be evaluated if the earth was laterally homogeneous and only the induction mode of the field was induced this paper presents the first results of the bimodal sounding based on s variation data an estimate of the lithosphere s transverse resistance t 3 x lo9 51 m2 has been obtained

regional distribution of deep clouds and cloud top altitudes over the indian subcontinent and the surrounding oceans 1 the bay of bengal bob and the east equatorial indian ocean are among the most intense deep convective regions over the tropics long term monthly mean distributions of deep clouds and the regional differences in the cloud top brightness temperature ctbt over the indian subcontinent and the surrounding oceanic regions the northern and eastern bob the southeast arabian sea and the eastern equatorial indian ocean are derived using national oceanic and atmospheric administration advanced very high resolution radiometer data for a period of 10 years and are compared with the direct observations of cloud top altitude cta using cloud aerosol lidar and infrared pathfinder satellite observation calipso the deepest clouds are found to occur over the northern bob nbob during the june august period the most probable ctbt in this region is 12 k lower than that over the other deep convective regions calipso observations also show that the frequency of occurrence of cta peaks at an altitude of 16 5 km over the nbob which is 1 km higher than that over the other regions strong convergence of horizontal wind between the surface and 200 hpa level and large divergence above combined with the most favorable sea surface temperature 28 c might be mainly responsible for the highest cta being observed over the nbob the annual variation of the base altitude and thickness of the tropical tropopause layer ttl and the upper tropospheric temperature are closely associated with the corresponding variations in the deep cloud fraction considerable fraction of deep clouds occurs within the ttl over the bob during the june august period

crumbling of dacite dome lava and generation of pyroclastic flows at unzen volcano recent modelling of volcanic eruptions has shown that the efficiency of subsurface degassing of magmas determines whether magma erupts explosively or effuses quietly1 2 slow uprise of magma is often accompanied by effective degassing leading to the extrusion of lava flows and domes although lava dome extrusion is one of the less explosive modes of eruption it is often accompanied by explosive pyroclastic activities3 5 the 1991 eruption of unzen volcano provided an opportunity to observe at close range several types of small scale pyroclastic flow glowing avalanches originating from lava domes most of the pyroclastic flows are of merapi type caused by blocks falling from a collapsing dome others are of pelean type originating in an explosion from the side of a dome the lavas apparently show variable degrees of self explosivity we suggest that variable degrees of degassing of the magma produced a wide range of excess pore pressures in the extruded lava domes resulting in both merapi type and pelean type pyroclastic flows from the domes

22 year survey of tropical convection penetrating into the lower stratosphere 1 a 22 year survey of tropical convection penetrating into the stratosphere has been conducted using special subsets of the international satellite cloud climatology project cloud data set in addition to refined information about the geographic distribution of penetrating convective systems these results show that penetrating convection occurs predominantly in the larger organized mesoscale convective systems whereas smaller unorganized convective systems rarely penetrate durations of penetrating events are longest for the largest systems hurricanes and typhoons generally exceeding one day

underestimation of deep convective cloud tops by thermal imagery 1 the most common method of ascertaining cloud heights from space is from thermal brightness temperatures deep convective clouds of high water content are expected to radiate as black bodies here thermal cloud top estimates from goes 8 are compared with direct estimates of where the top should be sensed based on colocated goddard cloud physics lidar cpl observations collected during the cirrus regional study of tropical anvils and florida area cirrus experiment crystal face goes 8 cloud top heights are consistently 1 km lower than the visible cloud top estimates from the lidar even though the latter take into account the finite visible opacity of the clouds and any overlying thin cirrus layers and are often far below the position of highest detected cloud the low bias in thermal estimates appears to get worse for the tallest clouds perhaps by an additional kilometer and depends little on cloud albedo the consistency of the bias over multiple satellites suggests that cloud retrievals are affected by an unexpected radiative transfer issue

generation of block and ash flows during the 1990 1995 eruption of unzen volcano japan processes generating block and ash flows by gravitational dome collapse merapi type pyroclastic flow were observed in detail during the 1990 1995 eruption of unzen volcano japan two different types were identified by analysis of video records and observations during helicopter flights most of the block and ash flows erupted during the 1991 1993 exogenous dome growth stage initially involved crack propagation due to cooling and flowage of the dome lava lobes the mass around the crack became unstable locally decreasing in tensile strength finally a slab separated from the lobe front fragmented progressively from the base to the top within a few seconds and became a block and ash flow rock falls immediately followed in response to local instability of the lobe front clasts in these rock falls fragmented and merged with the preceding flow in contrast block and ash flows during the endogenous dome growth stage in 1994 were generated due to local bulge of the dome unstable lava blocks collapsed and subsequently fragmented to produce block and ash flows

flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano at nw rota 1 are primarily h2o so2 and co2 instantaneous fluxes varied by a factor of 100 over the deployment using melt inclusion information to estimate the concentration of co2 in the explosive gases as 6 9 0 7 wt we calculate an annual co2 eruption flux of 0 4 0 1 tg a 1 this result is within the range of measured co2 fluxes at continuously erupting subaerial volcanoes and represents 0 2 0 6 of the annual estimated output of co2 from all subaerial arc volcanoes and 0 4 0 6 of the mid ocean ridge flux the multiyear eruptive history of nw rota 1 demonstrates that submarine volcanoes can be significant and sustained sources of co2 to the shallow ocean

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

seismic and acoustic signatures of surficial mass movements at volcanoes abstract surficial mass movements such as debris avalanches rock falls lahars pyroclastic flows and outburst floods are a dominant hazard at many volcanoes worldwide understanding these processes cataloging their spatio temporal occurrence and detecting tracking and characterizing these events would advance the science of volcano monitoring and help mitigate hazards seismic and acoustic methods show promise for achieving these objectives many surficial mass movements generate observable seismic and acoustic signals and many volcanoes are already monitored significant progress has been made toward understanding modeling and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements however much work remains in this paper we review the state of the art of the topic covering a range of scales and event types from individual rock falls to sector collapses we consider a full variety of volcanic settings from submarine to subaerial shield volcano to stratovolcano finally we discuss future directions toward operational seismo acoustic monitoring of surficial mass movements at volcanoes

origin of the sound generated by strombolian explosions during strombolian eruptions large bubbles break at the surface of the lava column and produce sound acoustic pressure recorded during several explosions on the eastern vent of stromboli volcano shows a pattern consistent between explosions the well marked oscillation contains only very low frequencies around 7 hz and is followed by a signal containing now both higher frequencies and lower frequency less than 4 hz the generation of sound is explained by the vibration 7 hz and bursting higher frequencies of large bubbles followed by the drainage of magma down in the conduit less than 4 hz the interpretation suggests that 1 the bubble vibrates before bursting and 2 the vibration prior to bursting yields more energy than the bursting itself the radius of bubbles responsible for explosions is determined to be close to 1 meter in agreement with observations of a few conduit sizes

monotonic infrasound and helmholtz resonance at volcan villarrica chile 1 monotonic infrasound with stable peaked frequency of 0 77 hz was recorded at volcan villarrica in january 2010 similar monotonic infrasound had been previously reported at villarrica e g ripepe et al 2010 using joint infrasound and visual observations from a suspended camera we demonstrate that the likely source of infrasound is helmholtz resonance produced from a cavity with volume 105 m3 that separates the active convecting lava lake from an overhanging spatter roof spatter roof dimension 65 m diameter and vent diameter 10 m in the roof are constrained from video observations assuming a cylindrical cavity we infer a cavity height of 31 m that is corroborated by video records of spatter drips the drips take as long as 2 2 s to fall from the roof into the lake corresponding to a height of more than 24 m which is in good agreement with the observed resonance frequency

characteristics of the double intertropical convergence zone over the tropical indian ocean 1 investigations on the double intertropical convergence zone ditcz over the indian ocean using the monthly mean surface wind divergence data obtained from scatterometers on board the ers 1 2 and quikscat satellites 1991 2005 and the monthly mean cloud amount obtained from the international satellite cloud climatology project 1988 1989 1998 2005 and the advanced very high resolution radiometer avhrr data 1996 2003 reveal that its frequency of occurrence is considerably larger than that reported earlier though the ditcz feature in this region is rather diffused compared to pacific the 14 year analysis of monthly mean surface wind divergence shows that ditcz structure is clearly discernible in april frequency of occurrence f 64 november f 73 and december f 60 in the 50 85 e longitude band over the tropical indian ocean though less frequent ditcz occur during other months also except the asian summer monsoon season most preferred latitudes of the north and south bands of ditcz are 6 n and 7 s respectively during november and december the ditcz structure is well manifested in the cloud amount also during november and december while it is less prominent in april a weak but clearly identifiable hemispherical asymmetry is observed in latitude of occurrence and amplitude of the ditcz bands since the sea surface temperature sst at the equatorial region over the indian ocean is nearly uniform the ditcz appears to be generated mainly by the atmospheric dynamics this provides a unique opportunity to investigate the structure of itcz created by the atmospheric dynamics alone which is one of the important problems in itcz dynamics

relationship between infrasound derived and buoyancy derived eruption plume volume estimates volume estimations for discrete plumes accompanying short lived eruptions are potentially possible using infrasound signals plumes emitted during short lived discrete eruptions have been modeled as discrete thermals or rooted thermals based on the one dimensional model for the rise of a discrete thermal the initial buoyancy f0 of a spherical thermal can theoretically be estimated from the maximum plume height and a vertical profile of ambient air density we here examine the relationship between infrasound derived volume vinf and the buoyancy derived volume vb as derived from f0 which depends on gravity acceleration and the difference in density between the thermal and surrounding air to understand how vinf relates to the dynamics of the eruption plume we analyze infrasound data accompanying vulcanian and phreatic eruptions at aso shinmoedake and lokon empung volcanoes to estimate vinf and consider vinf from other volcanoes we obtain a representative ratio of vb vinf of 16 by examining 53 events because the analyzed infrasound signals share a prominent pressure pulse at the onset we regard vinf as the volume of the plume at initiation i e as a jet instead we consider vb as the thermal volume when it has entrained a sufficient amount of the surrounding air and obtains f0 comparison of the bulk density of the jet and the discrete thermal yields a rate of volume change between both regimes by a factor of 1 8 32 which is consistent with the ratio of vb vinf our result provides an effective index to constrain erupted plume volume using infrasound data with real time monitoring systems

the electrical conductivity of the mantle beneath europe derived from c responses from 3 to 720 hr summary the c response which connects the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic fluctuations forms the basis for estimating the conductivity depth profile of the earth this paper describes new estimates of the c response obtained from observatory hourly mean values the z y method is applied which means that the vertical component is used locally whereas the horizontal components are used globally by expansion into terms of spherical harmonics a special evort is made to obtain unbiased estimates of c when applied to 90 months of hourly mean values from about 90 observatories the method yields consistent results for european observatories in the entire period range from 3 to 720 hr and for two diverent source mechanisms s and d st a good description of the source structure for individual time segments is essential this was achieved by a separate spherical harmonic analysis of the data for each month for d st or each day for s and by estimating a large number 120 of expansion coeycients the results are interpreted by means of 1 d conductivity models which show that the upper mantle has remarkably little structure with a monotonic decrease of resistivity from 100 v m near z 200 km to 0 7 v m below z 1000 km

behavior of deep convective clouds in the tropical pacific deduced from isccp radiances abstract we analyze the properties of deep convection over the equatorial pacific and its relationship to sea surface temperature sst and surface wind divergence using isccp radiance data for july 1983 and january 1984 deep convective clouds dcc are diagnosed with both a combined visible infrared threshold method and an infrared only threshold method the visible channel is important in diagnosing deep convection in different regions with different surface and atmospheric properties because of the existence of large scale variations of dcc top altitudes the itcz and spcz exhibit changes in these two months that are characteristic of both the el nino and seasonal cycles deep convection is latitudinally confined to a much smaller spatial scale than that suggested by maps of outgoing longwave radiation diurnal variations of dcc cover and associated mesoscale cirrus anvil cloud cac cover are out of phase with deep convection peaking in the early morning throughout the equatorial pacific the diurna

infrasonic precursors to a vulcanian eruption at sakurajima volcano japan the may 1998 eruption sequence of sakurajima volcano was monitored by ten infrasonic stations ten seismometers and a video camera during this seismo acoustic experiment we recorded hundreds of infrasonic tremor and long period events associated with seismic signals and observed a progression from relative quiescence to a vulcanian eruption the number of infrasonic events increased with escalating volcanic activity and the dominant character of the infrasonic signals changed from impulsive to emergent at 22 17 of may 19 sakurajima released ash and gases to a height of 2 km above the vent an event that was recorded continuously by one infrasonic and two seismic stations we present the experimental setup as well as a procedure through which infrasonic signals may be incorporated into future eruption monitoring and forecasting algorithms for open vent volcanic systems in addition our recordings suggest that infrasonic signals are more representative of processes occurring within the volcanic interior than are seismic signals which are strongly altered by diffraction and scattering in the volcanic edifice

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

emag2 a 2 arc min resolution earth magnetic anomaly grid compiled from satellite airborne and marine magnetic measurements 1 a global earth magnetic anomaly grid emag2 has been compiled from satellite ship and airborne magnetic measurements emag2 is a significant update of our previous candidate grid for the world digital magnetic anomaly map the resolution has been improved from 3 arc min to 2 arc min and the altitude has been reduced from 5 km to 4 km above the geoid additional grid and track line data have been included both over land and the oceans wherever available the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation based on an oceanic crustal age model the longest wavelengths 330 km were replaced with the latest champ satellite magnetic field model mf6 emag2 is available at http geomag org models emag2 and for permanent archive at http earthref org cgi bin er cgi s erda cgi n 970

day to day changes in the latitudes of the foci of the sq current system and their relation to equatorial electrojet strength 1 the latitudes of the foci of the sq current systems over australia and japan are determined on a daily basis during the period from december 1989 to june 1990 the availability of a dense network of observatories in australia during that time enabled a better determination in that region latitudinal movements of the foci are compared with the strength of the equatorial electrojet and generally an increase in electrojet strength is accompanied with a poleward movement of the focus especially in japan some examples are noted where the foci in the two hemispheres move poleward or equatorward together from one day to the next but this relationship was not found to be statistically significant it is hard to disentangle effects due to other current systems such as sqp from changes related to atmospheric tides if some of the observed effects are due to tides then the 2 3 and 2 4 semidiurnal modes are more likely contributors than the 2 2 mode

the distribution of deep convection over ocean and land during the asian summer monsoon abstract tle highly reflective cloud hrc dataset is a daily index of organized deep convection at one degree resolution from 17 years of polar orbiting satellite imagery these data are used to analyze and discuss the climatological geographical distribution of deep convection observed over the asian summer monsoon season and its component months june july august and september intraseasonal variations of convection for selected regions am examined using normalized pentad time series of regional median hrc values we also compare hrc data over two regions western coastal india and western coastal burma thailand with the results from a two dimensional numerical model consisting of a simple differentially heated land ocean system which predicts that a preponderance of deep convection occurs over the coastal zone the buma thailand regional comparison supports the model result comparison of the model with the western coastal india region is less conclusive which may be due to the limitations of

seismoacoustic investigations of paroxysmal activity at mt etna volcano new insights into the 16 november 2006 eruption 1 on 16 november 2006 a 1 day long paroxysmal eruption occurred at the summit craters of mt etna volcano a multiparametric approach consisting of analyzing infrasonic seismic and video camera recordings was carried out to follow its evolution volcanological and geophysical observations identified three eruptive phases in the first phase infrasonic and seismic characteristics reflected the highly explosive nature of the activity waveform characterization of infrasound events confirmed the activity of the several explosive vents at the summit of southeast crater sec during the second phase results highlighted the decoupling between seismic and infrasonic sources which was due to the decrease in explosive activity and the reactivation of effusive vents located south of bocca nuova and on the saddle between bocca nuova and sec the third phase was the most intense and was characterized by various volcanic phenomena pyroclastic flows jets of dark ash and white steam the very high radiated infrasonic energy together with infrasound event features led us to infer a gas enrichment of the shallow magma column preceding by a few minutes and likely related to the pyroclastic flows in the sec area after the eruption at sec variations in infrasound events related to the activity of northeast crater nec were found the observed spectral changes and the source mechanism modeling of the nec infrasound events suggest the existence of a link in the plumbing system feeding the two craters

spatiotemporal sampling of sq induced geomagnetic responses at leo satellite altitude for a radially conductive earth summary a new simulation tool is introduced for extracting earth conductivity information from geomagnetic satellites in low earth orbit leo such as champ swarm and potential follow on missions theoretical reconstruction of spherical harmonic spectra of global universal time ut geomagnetic field maps is analysed an idealized regular solar daily variation field is assumed along with its induced counterpart from a radially stratified earth solar quiet sq spectra can be reliably reconstructed from discrete time series of measurements sampled daily within a fixed ut window a single leo satellite should be in orbit for at least 1 yr under quiet time conditions to ensure accurate spectral reconstruction of an sq geomagnetic spectrum the length of the daily sampling window and random day to day variability in the sq source strength have only minor effects on spectral reconstruction the shape of the spectra and spectral ratios are independent of radial mantle conductivity further research employing 3 d forward modelling of induction in a laterally heterogeneous earth with more realistic and complete external source descriptions is advocated the new simulation tool should prove valuable to planners of future multisatellite geomagnetic missions as well as scientists interested in analysing and interpreting satellite induction signals

first continuous gps soundings of temperature structure over antarctic winter from formosat 3 cosmic constellation 1 the formosat 3 cosmic mission provides unprecedented spatial coverage of daily sounding profiles of the antarctic atmosphere our analysis shows that temperature profiles from these global positioning system gps soundings agree well with the radiosondes over the south pole and neumayer stations during the 2006 southern hemisphere sh winter season these gps soundings reveal a vertical domain of low temperature e g t 78 c at 28 km altitude that is not clearly defined by the antarctic radiosondes latitudinal analysis of the gps soundings shows that regions with t 78 c occur from about 10 km to 28 km altitudes indicating an 18 km thick of the cold vertical layer the extremely cold regions are found at latitudes between 71 s and 87 s and in altitudes between 15 and 25 km not coinciding with the geographical south pole these results demonstrate the potential of the formosat 3 cosmic data for polar studies

towards an automatic monitoring system of infrasonic events at mt etna strategies for source location and modeling active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes in this work we discuss the automatic procedures implemented for a real time application to the data acquired by a permanent network of five infrasound stations running at mt etna volcano the infrasound signals at mt etna consist in amplitude transients called infrasound events the adopted procedure uses a multi algorithm approach for event detection counting characterization and location it is designed for an efficient and accurate processing of infrasound records provided by single site and array stations moreover the source mechanism of these events can be investigated off line or in near real time by using three different models 1 strombolian bubble 2 resonating conduit and 3 helmholtz resonator the infrasound waveforms allow us to choose the most suitable model to get quantitative information about the source and to follow the time evolution of the source parameters

excitation process of infrasonic waves associated with merapi type pyroclastic flow as revealed by a new recording system we investigate excitation process of the infrasonic waves associated with merapi type pyroclastic flows at unzen volcano japan using data set obtained by a new system that permits recording of geophysical data with accompanying visual events on a single videotape the accurate correlation of infrasonic waves with video images reveals that 1 successive impulsive waves and the low frequency wave 0 8hz are excited during the collapse of lava blocks falling from the dome which generates a pyroclastic flow 2 an impulsive wave is excited by an explosive blowout of the pore gases which are released by the breakdown of the falling blocks 3 the low frequency wave is excited by the volumetric change which results from expansion of the pore gases released by pulverization of the falling blocks the comparison between the observed and the synthetic low frequency waves shows that the amount of volume change is about 2 times that of the initial falling blocks

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

a global study of volcanic infrasound characteristics and the potential for long range monitoring abstract volcanic infrasound from explosive eruptions is detectable at distances up to 1000 s of km and is often recorded on the international monitoring system ims infrasound network though infrasound produced by individual volcanoes has previously been studied more general relationships between infrasound characteristics and eruption parameters remain unclear therefore using a dataset comprising 110 events at 39 globally distributed volcanoes we assess the ability of the ims to monitor remote volcanoes and investigate whether volcanic infrasound exhibits consistent trends across a range of eruption styles and intensities acoustic pressure amplitude and frequency content of the volcanic infrasound were measured and acoustic energy was also calculated these were compared along with the maximum distance of detection for each event to the maximum plume height reported for the event which was used as a proxy for event intensity of the events investigated 62 were detected by at least one infrasound station the maximum distance at which an event was detected generally increased with the plume height and infrasound produced during the eruption of manam png in january 2005 which produced a plume which rose over 20 km above the summit was detected at a distance of 10 671 km total acoustic energy and acoustic pressure amplitude corrected for geometrical spreading increased with plume height whilst the lowest frequency present in the volcanic infrasound decreased additionally relationships seen between infrasound characteristics and eruption plume height indicate that analyses of this data alone could constrain vital estimates of plume heights for otherwise un observed eruptions taken together these findings indicate that if made available for this purpose in the future the ims infrasound network could complement existing monitoring techniques by detecting and characterising eruptions at remote volcanoes which often have no local monitoring networks