solar and lunar tidal variabilities in gps tec and geomagnetic field variations seasonal as well as during the sudden stratospheric warming of 2010 the global positioning system gps deduced total electron content tec data at 15 n geomagnetic which is the northern crest region of equatorial ionization anomaly are used to study solar and lunar tidal variabilities during the years 2008 and 2009 and also during the 2009 2010 winter when a major sudden stratospheric warming ssw event has occurred the diurnal and semidiurnal tidal amplitudes show semiannual variation with maximum amplitudes during february march and september november whereas terdiurnal tide is larger during april september they show significant longitudinal variability with larger smaller amplitudes over 250 e 150 e 200 e 250 e lunar semidiurnal tidal amplitudes show sporadic enhancements during northern winter months and negligible amplitudes during northern summer months they also show notable longitudinal variabilities the solar migrating tides dw1 and sw2 show semiannual variation with larger amplitudes during spring equinox months whereas tw3 maximizes during northern summer dw2 shows larger amplitudes during summer months during the ssw except tw3 the migrating tides dw1 and sw2 show considerable enhancements among solar nonmigrating tides sw1 tw2 and ds0 show larger enhancements solar tides in tec and equatorial electrojet strength over tirunelveli vary with the time scale of 60 days during october 2009 march 2010 similar to ozone mass mixing ratio at 10 hpa and this confirms the vital role of ozone in tidal variabilities in ionospheric parameters lunar tidal amplitudes in changes in horizontal component of geomagnetic field h are larger over tirunelveli a station near dip equator solar semidiurnal tides in h have larger amplitudes than lunar tides over polar stations mawson and godhavn

unexpected characteristics of the 150 km echoes observed over gadanki and their implications recent discovery of two distinct types of 150 km echoes namely type a and type b and subsequent progress in the large scale kinetic simulation of photoelectron induced plasma waves have begun a new era in resolving the five decades long 150 km echoing riddle in this paper we present hitherto unrevealed three important and unexpected findings on the two distinct types of 150 km echoes based on gadanki radar observations our observations show unexpected predominance of type a echoes strong seasonal dependence of both type a and type b echoes and a surprising connection of the type b echoes to the unusually deep solar minimum of 2008 2009 we discuss how these results provide important new clues in tethering the competing processes involved in the daytime 150 km echoes and have significance in the recently proposed photoelectron induced plasma fluctuations as a potential mechanism for the 150 km echoes

radar interferometric mapping of deformation in the year after the landers earthquake although the 1992 landers california earthquake sequence occurred in an area well sampled by geodetic networks1 3 the postseismic deformation in the months following the earthquake has been measured at only 15 geodetic stations4 another shortcoming in the geodetic coverage occurs west of the primary rupture where the existing geodetic observations suggest but cannot resolve sympathetic slip on secondary faults1 such measurements which are needed to place the landers earthquake sequence in the context of a recurring seismic cycle in california can be obtained with the dense spatial coverage provided by satellite radar interferometry5 9 here we present radar maps of the surface deformation field which reveal features that would otherwise have been poorly sampled particularly if the earthquake had occurred in a less accessible area we see triggered slip at the level of several centimetres as far as 100 km from the primary rupture and can resolve the geodetic signal of at least one small magnitude 5 aftershock the amount of surface slip following the main shock is less than a decimetre and is consistent with an exponential decay time of several months for the postseismic deformation

a study of a self generated stratospheric sudden warming and its mesospheric lower thermospheric impacts using the coupled time gcm ccm3 1 a stratospheric sudden warming episode was self consistently generated in the coupled national center for atmospheric research thermosphere ionosphere mesosphere and electrodynamics general circulation model climate community model version 3 time gcm ccm3 taking advantage of the unique vertical range of the coupled model ground to 500 km we were able to study the coupling of the lower and upper atmosphere in this warming episode planetary wave 1 is the dominant wave component in this warming event analysis of the wave phase structure and the wave amplitude indicates that the wave may experience resonant amplification prior to the peak warming the mean wind in the high latitude winter stratopause and mesosphere decelerates and reverses to westward due to planetary wave forcing and forms a critical layer near the zero wind lines the wind deceleration and reversal also change the filtering of gravity waves by allowing more eastward gravity waves to propagate into the mesosphere and lower thermosphere mlt which causes eastward forcing and reverses the westward jet in the mlt this also changes the meridional circulation in the upper mesosphere from poleward downward to equatorward upward causing a depletion of the peak atomic oxygen layer at 97 km and significant reduction of green line airglow emission at high latitudes and midlatitudes planetary waves forced in situ by filtered gravity waves in the mlt grow in the warming episode their growth and interaction with tides create diurnal and semidiurnal variabilities in the zonal mean zonal wind

variabilities of low latitude migrating and nonmigrating tides in gps tec and timed saber temperature during the sudden stratospheric warming event of 2013 the global positioning system gps deduced total electron content tec data at 15 n geomagnetic which is the crest region of equatorial ionization anomaly are used to study tidal variabilities during the 2013 sudden stratospheric warming ssw event the results from space time spectral analysis reveal that the amplitudes of migrating diurnal dw1 and semi diurnal sw2 tides are larger than those of non migrating tides after the ssw onset the amplitudes of dw1 sw2 sw1 and ds0 increase moreover they show 16 day variations similar to the periodicity of the high latitude stratospheric planetary wave pw suggesting that the non migrating tides sw1 and ds0 are possibly generated due to non linear interaction of migrating tides with pw similar spectral analysis on temperature at 10 n obtained from the sounding of atmosphere by broadband emission radiometry saber shows that the sw2 enhances at stratospheric heights and the sw2 is more dominant at 80 90 km but its amplitude decreases around 100 km the amplitudes of non migrating tides become comparable to those of sw2 around 100 km and their contribution become increasingly important at higher heights this suggests that the non linear interaction between migrating tides and pw occur at low latitude upper mesospheric heights as sw2 exhibits 16 day periodicity in saber temperature at 100 km as observed in tec besides it is observed that the eastward propagating tides are less dominant than westward propagating tides in both tec and saber temperature

a global view of the atmospheric lunar semidiurnal tide 1 atmospheric lunar semidiurnal tides are studied using 10 years of temperature data collected by the thermosphere ionosphere mesosphere energetics and dynamics sounding of the atmosphere using broadband emission radiometry satellite the amplitudes and phases in the temperature field are calculated by performing least mean square fit in a data set of about 60 day interval combining ascending and descending data together the mean tidal structures are studied for the height range from 20 to 120 km between 50 latitude and centered on each month from february 2002 to january 2012 a clear signature of the 12 42 h lunar semidiurnal tide is observed in the data characteristic of propagating waves is observed in the vertical amplitude and phase profiles in almost all heights the best conditions of propagation for the lunar semidiurnal tide are reached in the lower thermosphere region asymmetry between the hemispheres and seasonal variability is observed in the amplitudes of the tide longitudinal variations are also observed which reveals the existence of nonmigrating components in addition to the dominant migrating lunar tide

descending ion layer property in the gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon 1 gadanki radar observations of the daytime 150 km echoes displaying descending features resembling the descending ion layer behavior are presented the descending pattern is intriguing since it indicates the possible role of density gradient associated with the ion layer in generating the irregularities responsible for 150 km radar echoes not envisioned before unusually strong snr and narrow spectral features of these echoes clearly indicate the role of sharp density gradients in the echoing process given the fact that gadanki is located at magnetically low latitude it is argued that these descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal gravity waves quite similar to that observed during nighttime the observations reported here are first of its kind illustrating the role of density gradient layers and are important in furthering our understanding on the puzzling 150 km echoing phenomenon

lunar tide in the thermosphere and weakening of the northern polar vortex the lunar tide and its variability are beginning to be realized as elements of ionosphere thermosphere weather herein we demonstrate that an enhancement in m 2 amplitude at 110 km in the dynamo region is related to the timing and intensity of stratospheric polar vortex weakening pvw timing of the pvw which typically occurs during january february changes on the order of 4 7 d yr between 2002 and 2013 and the m2 enhancement changes with it with a time delay of order 2 8 days the m2 temperature amplitude at 110 km as determined from the sounding of the atmosphere using broadband emission radiometry saber measurements on the thermosphere ionosphere mesosphere energetics dynamics timed spacecraft increases linearly from about 20 k to 29 k as the westward zonal mean zonal wind increases from about 10 m s 1 to 80 ms 1 at 70 n and 48 km altitude in accord with pvw events from year to year according to modern era retrospective analysis for research and applications merra data these relationships point to a level of predictability regarding impacts of the lunar tide on thermosphere and ionosphere densities winds and plasma drifts

high resolution observations of 150 km echoes at jicamarca high resolution soundings of equatorial upper e region echoes at jicamarca exhibit gravity wave modulated signal intensity distributions and doppler velocities corresponding to vertical plasma drifts a gravity wave wind driven interchange instability is suggested as a possible generation mechanism of the field aligned plasma irregularities responsible for the echoes the echoes may be utilized in gravity wave studies and in zonal electric field measurements by radars with modest sensitivities

terdiurnal migrating tide signature in ionospheric total electron content we report the latitudinal seasonal and solar cycle variations of terdiurnal migrating tide i e terdiurnal westward wave number 3 tw3 signature in ionospheric total electron content tec our investigations are based on the jpl global ionospheric maps gims during 1999 2011 the absolute amplitude of tw3 exhibits maximum values in the magnetic equatorial region which reaches about 8 tecu under high solar activity and 1 5 tecu under low solar activity the relative amplitude of zonal mean tec in equatorial region however shows persistent patterns from 1999 to 2011 with little solar activity dependence the relative amplitude of tw3 has a peak of similar to 10 in the magnetic equatorial region and a second one of similar to 7 at magnetic middle latitudes 30 degrees 50 degrees at high latitudes in local winter seasons the maximum relative amplitude occurs which varies between 8 and 15 with slightly larger amplitudes in the northern hemisphere the global structure of tw3 signature in tec should shed some light on the coupling between the ionosphere thermosphere and the lower atmosphere

observational evidence of ionospheric migrating tide modification during the 2009 stratospheric sudden warming 1 in this paper modifications of the ionospheric tidal signatures during the 2009 stratospheric sudden warming ssw event are studied by applying atmospheric tidal analysis to ionospheric electron densities observed using radio occultation soundings of formosat 3 cosmic the tidal analysis indicates that the zonal mean and major migrating tidal components dw1 sw2 and tw3 decrease around the time of the ssw with 1 5 4 hour time shifts in the daily time of maximum around eia and middle latitudes the typical ionospheric ssw signature a semi diurnal variation of the ionospheric electron density featuring an earlier commencement and subsidence of eia can be reproduced by differencing the migrating tides before and during the ssw period our results also indicate that the migrating tides represent 80 of the ionospheric tidal components at specific longitudes suggesting that modifications of the migrating tides may be the major driver for producing ionospheric changes observed during ssw events accounting for greater variability than the nonmigrating tides that have been the focus of previous studies

lunar and solar tidal variabilities in mesospheric winds and eej strength over tirunelveli 8 7 n 77 8 e during the 2009 major stratospheric warming 1 mesospheric wind observations by the medium frequency radar and geomagnetic field observations at tirunelveli 8 7 n 77 8 e 1 75 n dip angle are used to study the relative importance of solar and lunar influences in the variabilities of mesospheric tides and equatorial electrojet eej strength during the unprecedented major stratospheric sudden warming ssw of 2009 it is observed that the afternoon reversal in the eej popularly known as counter electrojet occurs consecutively for several days during the ssw event when there is an enhancement of solar semidiurnal tide in both zonal wind at 90 km and eej strength over tirunelveli although the amplitude of lunar tides also shows enhancement it is much less than that of solar the diurnal tidal amplitude in zonal wind and eej strength also shows large enhancement just before the onset of ssw however solar semidiurnal tide dominates diurnal tide during the ssw the diurnal tidal phase in zonal wind shifts to a few hours earlier during the ssw the lunar semidiurnal tidal phase shifts to later hours in both zonal wind and eej strength the main observation of the present study is that the large semidiurnal tide observed during the ssw 2009 is mostly solar driven and only partly lunar driven although tidal planetary wave interaction also may play a vital role although a similar behavior is noticed during the ssw 2006 also the large lunar semidiurnal tide observed in the eej strength without having large lunar semidiurnal tide in the underlying mesospheric winds needs further investigation

global structure of the lunar tide in ionospheric total electron content 1 the global structure of the lunar tide in the ionosphere is studied based on observations of the global positioning system gps total electron content tec the unprecedented spatial and temporal resolution afforded by the gps tec observations enables illustration of the latitude longitude solar local time and seasonal variability of the lunar tide in the ionosphere based on analysis of the multi year mean from 1999 2008 the dominant component is generally the semidiurnal lunar tide however a significant diurnal variation is also observed in some instances the semidiurnal component achieves a maximum amplitude of 6 in the equatorial ionization anomaly crest regions and a slight hemispheric asymmetry is present with larger amplitudes in the northern hemisphere furthermore the maximum amplitudes in the semidiurnal lunar tide are found to occur during northern hemisphere winter and during 9 15 solar local time during certain years a secondary maxima in solar local time is also observed demonstrating the influence of the lunar tide on the prereversal enhancement lastly the observations reveal significant longitudinal variability in the semidiurnal lunar tide that is most prominent between november and february the presence of a longitudinal variation reveals the existence of nonmigrating components in addition to the dominant migrating semidiurnal lunar tide

evidence for stratosphere sudden warming ionosphere coupling due to vertically propagating tides 1 observations of the global positioning system gps total electron content tec are used to study the coupling between the 2009 sudden stratospheric warming ssw and ionospheric perturbations the observations reveal both migrating and nonmigrating perturbations to the semidiurnal tide in the equatorial ionization anomaly crest region that are associated with changes in electric fields induced by the tidal dynamo in particular a significant enhancement is observed in the nonmigrating semidiurnal westward propagating tide with zonal wavenumber 1 sw1 in gps tec during the ssw the sw1 perturbations in the low latitude ionosphere are found to oscillate with a similar period as planetary wave 1 activity in the northern hemisphere stratosphere this connection is attributed to the nonlinear interaction between tides and planetary waves and strongly supports the theory that planetary wave tide interaction is the primary mechanism coupling ssws to ionospheric variability enhancements are also observed in the nonmigrating semidiurnal tide with zonal wavenumber 0 s0 during this time period and may be related to the nonlinear interaction between the migrating semidiurnal tide and planetary wave 2 the connection between planetary wave 2 and s0 is however less clear which may be attributed to differences in the zonal mean zonal winds in the mesosphere and lower thermosphere during the times of peak planetary wave 1 and planetary wave 2 activity we conclude that the changing zonal winds during ssws play an important role in the coupling between ionospheric variability and the forcing from planetary waves of lower atmospheric origin during ssws

on a summer maximum in the occurrence frequency of 150 km f1 radar echoes over pohnpei 1 using three and a half years of 50 mhz radar data collected from pohnpei federated states of micronesia 6 96 n 158 19 e geographic 0 3 magnetic dip latitude we show for the first time that the occurrence frequency of 150 km or f1 echoes has a broad but conspicuous maximum during northern summer in this longitude sector with minimal activity in other months given a seasonal similarity to sporadic e es we suggest that an es layer instability cosgrove and tsunoda 2002 generates a polarization electric field which maps along geomagnetic field lines to the f1 region there forms thin plasma sheets that provide gradients to excite 3 m scale plasma waves via an interchange process

lunar tide in the equatorial electrojet in relation to stratospheric warmings 1 the relationship between sudden stratospheric warmings ssws and large amplitude lunar tides in the equatorial electrojet eej is studied analysis of ground magnetometer data shows that the lunar tide in the eej is maximum during the northern winter season except in the pacific ocean region since ssws are also a northern winter phenomenon it is suggested that the relation between the large lunar tide in the eej and the ssw may possibly be coincidental the lunar tide in the geomagnetic variations at huancayo is anomalously large compared with other eej stations an examination of geomagnetic variations at eej stations during ssw events shows that afternoon counter electrojets are frequently present at new moon and full moon though the relationship is sometimes broken the observation of large lunar eejs when no ssw is present and of various different delay times suggests that other atmospheric processes are likely to be in play

quiet variability of equatorial e b drifts during a sudden stratospheric warming event 1 we present strong evidence that during the january 2008 minor sudden stratospheric warming ssw event the equatorial vertical e b drifts exhibit a unique and distinctive daytime pattern we do not think one event causes the other however both events might be related through the global effects of planetary waves the drifts were measured by the jicamarca incoherent scatter radar located under the magnetic equator we have observed an anomalous temporal variation of the vertical e b drifts during the minor ssw event showing a semidiurnal variation with very large amplitudes lasting for several days large differences in the e b drifts were observed during a period of large increase of temperature and a large decrease of mean zonal wind in the high latitude stratosphere 60 90 n this high correlation is an unexpected finding which might shed new light on sources and mechanisms of quiet time ionospheric variability

upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events in recent years there have been a series of reported ground and satellite based observations of lunar tide signatures in the equatorial and low latitude ionosphere thermosphere around sudden stratospheric warming ssw events this lower atmosphere ionosphere coupling has been suggested to be via the e region dynamo in this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude 54 n station and a high latitude 69 n station instead of correlating our results with typical definitions of ssws we use the definition of polar vortex weaking pvw used by zhang and forbes 2014 this definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the e region we have performed a wave decomposition on hourly wind data in 21 day segments shifted by 1 day in addition to the radar wind data the analysis has been applied to simulations from whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model our results indicate that the semidiurnal lunar tide m2 enhances in northern hemispheric winter months over both middle and high latitudes the time and magnitude of m2 are highly correlated with the time and associated zonal wind of pvw at middle high latitudes m2 in the upper mesosphere occurs after before the pvw at both latitudes the maximum amplitude of m2 is directly proportional to the strength of pvw westward wind we have found that m2 amplitudes could be comparable to semidiurnal solar tide amplitudes particularly around pvw and equinoxes besides these general results we have also found peculiarities in some events particularly at high latitudes these peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions for example during ssw 2009 we found that m2 enhances many days before pvw which is not in agreement with most of our results

monthly tidal temperatures 20 120 km from timed saber 1 the saber instrument on the timed satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides however the slow local time precession rate of timed can cause longer term temperature variations to alias into the tidal signals a new method of analyzing satellite data for tides has been developed to circumvent this difficulty but at the expense of temporal resolution of the tidal fields i e 120 day mean tidal structures are obtained in this work we apply this method to saber temperature data to derive a series of 120 day mean tidal structures extending between 20 and 120 km altitude 50 s 50 n latitude and centered on each month from september 2003 to september 2004 in addition to the migrating sun synchronous diurnal and semidiurnal tides a number of nonmigrating tides are revealed in the saber measurements some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s 1 other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection of the latter the eastward propagating diurnal tide with s 3 is dominant and is as large as the migrating diurnal tide during some months of particular interest is the wave 4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields this feature is a result of the predominant wave 4 topography land sea longitude dependence at the surface which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection the ability of the global scale wave model gswm to approximate the observed tidal fields including the wave 4 total tidal structures is also assessed

long term variability of the low latitude mesospheric sao and qbo and their relation with stratospheric qbo 1 long term variations of low latitude mesospheric semi annual oscillation msao and quasi biennial oscillation mqbo in the zonal wind are studied using observations available from 1977 to 2006 the mqbo showed large inter annual variability in the phase difference between 77 5 km and 72 5 km indicating such variability in eddy viscosity association of these oscillations with stratospheric quasi biennial oscillation sqbo is investigated in general the mqbo at 77 5 km is out of phase with sqbo and this relation fails during strong and long sqbo the msao at 72 5 km and 77 5 km generally shows strong westward phase during strong eastward phase of sqbo the most striking feature observed in the present study is the strong modulation of the msao by mqbo revealing a non linear type of interaction with presence of sidebands of the msao

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

radar observations of daytime 150 km echoes from outside the equatorial electrojet belt over gadanki 1 we present systematic observations of daytime 150 km echoes from gadanki 13 5 n 79 2 e 6 3 dip latitude the echoing region is confined to 142 162 km altitude and show forenoon descent and afternoon ascent displaying a necklace shape quite similar to that of the equatorial 150 km echoes signal to noise ratio velocity and spectral width are as high as 13 db above noise 5 to 35 m s 1 and 2 to15 m s 1 respectively the observed necklace shape is first of its kind from gadanki and the present observations have almost all characteristics of equatorial daytime 150 km echoes the gadanki radar observations hence provide first experimental evidence on the occurrence of daytime 150 km echoes outside the equatorial electrojet belt

equatorial 150 km irregularities observed at pohnpei first observations of meter scale equatorial 150 km plasma irregularities outside the american longitude sector are reported the observations conducted at pohnpei western pacific with a wind profiling st radar demonstrate the feasibility of making ionospheric electric field measurements with low cost instruments and also reveal a potentially important anisotropy in the angular distribution of 150 km vhf radar echoes

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

equatorial electrodynamics and neutral background in the asian sector during the 2009 stratospheric sudden warming using ground observations of total electron content tec and equatorial electrojet eej in the asian sector along with plasma and neutral densities obtained from the champ satellite we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming ssw in january 2009 our analysis reveals the following prominent features first the tec response in tropical regions is strongly latitude dependent with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes second the tec semidiurnal perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude it starts on the same day as the ssw peak in the northern hemisphere but 2 days later in the southern hemisphere its magnitude is twice as strong in the north than in the south third strong counter electrojet occurs in the afternoon following the strengthening of the eastward eej in the morning fourth semidiurnal perturbation in both tec and eej possesses a phase shift at a rate of about 0 7 h day comparisons with results reported in the peruvian sector reveal clear longitude dependence in the amplitude and hemispheric asymmetry of the semidiurnal perturbation finally thermospheric density undergoes 25 decrease at low latitudes in the afternoon local time sector during the ssw indicating significant cooling effects in the tropical upper thermosphere

on the linkage of daytime 150 km echoes and abnormal intermediate layer traces over sanya 1 the daytime 150 km echoes which are associated with the upper e region field aligned irregularities have been observed around the equatorial electrojet region but never before at magnetic latitudes near the northern anomaly crest region we present first results of daytime 150 km echo over sanya china a station located far away from the dip equator in the northern hemisphere a layer of weak radar echoes with spectral width less than 10 m s 1 was seen in the height range from 145 km at 12 15 lt to 152 km at 13 45 lt on 21 july 2010 the interesting aspect is that the rare observation of daytime 150 km echoes with the small sanya vhf radar was preceded by the occurrence of an unusual intermediate layer which is identified as abnormal traces at the upper e region in corresponding ionograms the abnormal intermediate layer associated with possible gravity wave activity that implicates the presence of upper e region density gradients could make a significant contribution to the growth of irregularities responsible for the rarely detected daytime 150 km echoes over sanya

on the sheet like nature of 150 km f1 radar echoes 1 the so called 150 km or f1 echoes are shown to arise from field aligned irregularities fai that are embedded in a sheet like region using a 49 92 mhz radar on christmas island which has an antenna beam directed toward geographic east at a zenith angle of 29 5 high resolution doppler velocity variations within the radar scattering volume are used to infer that the sheet like region could have both tilt and curvature this finding is used to infer that plasma density n must be enhanced within the sheet like region and that fai could be generated by an interchange instability driven by a vertical electric field or a zonal neutral wind that acts on the horizontal component of the gradient in n how tilted sheet like structures could form in the f1 region is discussed

co seismic displacements of the 1992 landers earthquake sequence we present co seismic displacement vectors derived from global positioning system gps measurements of 92 stations in southern california these gps results are combined with five well determined gps displacement vectors from continuously tracking stations of the permanent gps geodetic array as well as line length changes from usgs geodolite and two color laser trilateration observations to determine a self consistent set of geodetic data for the earthquake these combined displacements are modeled by an elastic dislocation representation of the primary fault rupture planes on average the model residuals are about twice the estimated measurement errors

daytime 150 km echoes observed with the equatorial atmosphere radar in indonesia first results 1 results of the daytime 150 km echoes from 10 36 s magnetic latitude observed using the equatorial atmosphere radar ear which are first of its kind from magnetic southern hemisphere are presented the echoing region of 145 165 km shows forenoon descent and afternoon ascent with signal intensity modulation with time resembling a necklace and the doppler spectra are narrow which are quite similar to those reported earlier from other locations westward and upward southward irregularity drifts are found to be consistent with daytime background electric fields providing a tool to investigate low latitude daytime electrodynamics detectability of these echoes suggests the absence of strong latitudinal dependence in contrast to the earlier belief suggesting a possibility of their detection at mid latitudes also the echoes show zonal anisotropy that is opposite to that observed over pohnpei the implications of these observations are discussed in the light of present understanding of 150 km echoing phenomenon

sudden stratospheric warming event signatures in daytime exb drift velocities in the peruvian and philippine longitude sectors for january 2003 and 2004 1 this paper first describes the technique that has been developed to obtain realistic daytime vertical exb drift velocities in the equatorial ionosphere using two ground based magnetometers one on the magnetic equator and the other located 6 9 away in latitude this technique is then employed to study the unique exb drift signatures associated with sudden stratospheric warming events ssw in both the peruvian and philippine longitude sectors occurring in january 2003 and january 2004 it is found that the semidiurnal shaped signature first appears in the peruvian sector and 3 days later appears in the philippine sector in both sectors the exb drift signature lasts for approximately 5 days

nonmigrating diurnal tides in the thermosphere 1 horizontal wind measurements from the hrdi and windii instruments on the upper atmosphere research satellite are analyzed to reveal the most prominent nonmigrating diurnal tidal components at 95 km the eastward propagating diurnal tide with zonal wave number s 3 de3 the standing s 0 diurnal oscillation d0 and the westward propagating diurnal tide with s 2 dw2 the strongest de3 occurs primarily during northern hemisphere summer fall with maximum eastward winds near the equator of order 15 ms 1 and is a vertical extension of the s 3 kelvin wave the first antisymmetric mode of de3 dominates during october april with maximum meridional winds near the equator of order 8 ms 1 d0 exists during nearly all months and is nonsymmetric about the equator with maximum northward wind amplitudes in the southern hemisphere of order 7 10 ms 1 dw2 closely resembles the first symmetric propagating mode from classical tidal theory with maximum northward wind amplitudes of order 10 12 ms 1 during september through february the combination of de3 d0 and dw2 with dw1 gives rise to significant longitude variations in the diurnal tide between 40 latitude forcing in the global scale wave model gswm is calibrated according to the above observations thus enabling global estimates of nonmigrating tidal temperatures and other fields for instance it is estimated that the temperature and eastward wind perturbations associated with de3 may be as large as 20k and 35 ms 1 at 145 km and 115 km respectively over the equatorial region during july

planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 1 the vertical coupling of the stratosphere mesosphere system through quasi stationary and traveling planetary waves during the major sudden stratospheric warming ssw in the arctic winter of 2003 2004 has been studied using three types of data the uk met office ukmo assimilated data set was used to examine the features of the global scale planetary disturbances present in the winter stratosphere of the northern hemisphere sounding the atmosphere using broadband emission radiometry saber satellite measurements were used as well for extracting the stationary planetary waves in the zonal and meridional winds of the stratosphere and mesosphere radar measurements at eight stations four of them situated at high latitudes 63 69n and the other four at midlatitudes 52 55n were used to determine planetary waves in the mesosphere lower thermosphere mlt the basic results show that prior to the ssw the stratospheremesosphere system was dominated by an upward and westward propagating 16 day wave detected simultaneously in the ukmo and mlt zonal and meridional wind data after the onset of the ssw longer period 22 24 days oscillations were observed in the zonal and meridional mlt winds these likely include the upward propagation of stationary planetary waves from below and in situ generation of disturbances by the dissipation and breaking of gravity waves filtered by stratospheric winds citation pancheva d et al 2008 planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 j geophys res 113 d12105 doi 10 1029 2007jd009011

effect of sudden stratospheric warming on lunar tidal modulation of the equatorial electrojet 1 using the equatorial electrojet eej peak current intensity as deduced from champ magnetic observations from the years 2001 through 2009 we investigated the relationship between sudden stratospheric warming ssw and lunitidal signatures in the tropical ionosphere there is a practically one to one correspondence between midwinter ssw periods and the strongest 13 day modulation of the eej strength as observed by champ that is all the midwinter ssw periods from december 2001 to august 2009 were accompanied by an enhanced 13 day modulation of the eej strength no other geophysical phenomenon brought about as strong a 13 day modulation as those of the midwinter ssw periods during each midwinter ssw period the amplified 13 day modulation of the eej strengths starts roughly within 1 week around the first peak in stratospheric temperature difference an oscillation with a period of 13 26 days is predicted by the lunitidal equation when considering the precession of the champ orbit when fitting the lunitidal equation to the eej modulations during the midwinter ssw periods consistent phase delays of 4 4 0 3 days of the tidal signal emerge for all the cases the results suggest that the pronounced 13 day modulation of the eej strength is related to an enhancement of the lunar tide in the ionosphere by the ssw effect