migrating and nonmigrating semidiurnal tides in the upper atmosphere excited by tropospheric latent heat release migrating and nonmigrating semidiurnal tides

formal inversion of isc arrival times for mantle p velocity structure summary seismic traveltime data are used to determine and assess a weighted least squares model of the 3 d p velocity structure of the earth s mantle a total of 682090 summary rays constructed from over three million isc traveltime observations are used to constrain velocity perturbations in 124966 by 6 cells an iterative block lu decomposition procedure applied on the massively parallel connection machine 2 cm 2 is used to compute a formal weighted least squares model of p velocity variations as well as the full resolution and covariance matrices it is found that the shallow mantle beneath the continents of the northern hemisphere is well resolved however the majority of mid oceanic features such as spreading ridges and hot spots are not well constrained as a function of depth the resolution is highest in the upper to mid mantle due to variations in ray coverage primarily because of ray geometry single blocks are not resolved below 1870km the estimates of spatial resolution constructed from the complete resolution matrix are useful in judging whether subducting lithosphere extends into the lower mantle the results indicate that possible extensions of subduction zones in the northern hemisphere are imaged reliably down to at least 1470 km however areas beneath most subduction zones in the southern hemisphere are averaged over scale lengths of 800km or more below a depth of 1070km velocity estimates for the mid to lower mantle beneath hawaii are the result of averaging over 1900 km or more generally vertical and lateral averaging of 600 to lo00 km is occurring in the depth range 2270 to 2670km p wave velocity values in the region just above the core mantle boundary cmb are large scale spatial averages 1500 km or more and individual cells are poorly resolved the model parameter standard error remains moderate throughout the lower mantle due to smaller traveltime errors associated with rays that bottom in this region these standard errors reach no more than 0 3 per cent of the jeffreys bullen average velocity the greatest standard errors 0 9 per cent of the average velocity are found in the upper mantle underlying the pacific basin these large parameter errors are due primarily to the poor ray coverage in the pacific coupled with the large arrival time uncertainties for p recordings in the epicentral distance range 0 to 20 the upper 200 km of the weighted least squares velocity model correlates strongly with known tectonic features a circum pacific ring of low velocity with a maximum of 2 per cent dominates the surface anomalies the most likely origin of this feature are the high temperatures associated with back arc magmatism the most conspicuous mid ocean velocity anomaly is iceland which appears as a strong low velocity region extending over many cells continental cratons appear as positive velocity 1 2 per cent anomalies extending to depths of 200 to 400km low velocities underly the continents of eurasia and north america at a depth range of 400 to 670 km in the mid mantle 670 to 1270 km deep a 1 2 per cent fast velocity anomaly encircles the region below the pacific basin a fast anomaly also underlies

dependence of thermospheric zonal winds on solar flux geomagnetic activity and hemisphere as measured by champ the thermospheric zonal winds measured by the champ satellite are used to statistically determine climatology under quiet and active geomagnetic conditions by collectively analyzing the bin averaged wind trend with f10 7 and the solar induced difference in wind structures the solar flux dependence of global thermosphere zonal wind is determined the increase of solar flux enhances the eastward winds at low latitudes from 18 06 mlt the increased ion drag reduces the night time eastward wind in the subauroral latitudes and the daytime westward winds from 06 08 mlt at all latitudes decrease with increasing solar flux zonal winds show coupled seasonal extreme ultraviolet euv dependency the equatorial zonal winds from 18 04 mlt indicate weaker eastward winds during the june solstice at high solar flux levels quiet time eastward winds at subauroral latitudes from 16 20 mlt are further decreased in the winter hemisphere influenced by asymmetries in solar illumination and the magnetic field zonal winds show hemispheric asymmetries quiet daytime winds are additionally influenced by solar illumination effects and the westward winds at the middle and subauroral latitudes are always stronger in the summer the night time eastward winds are higher in the winter hemisphere during the solstices as in the southern hemisphere during equinoxes with the winter summer asymmetry lessened or receding at the solar maxima storm induced subauroral westward disturbance winds are higher in the summer hemisphere and in the northern hemisphere during equinoxes at a high level of solar flux the westward disturbance winds are comparable in the two hemispheres during december solstice geomagnetic disturbance wind observations from champ agree well with the empirical geomagnetic disturbance wind model dwm07 except for stronger subauroral westward jets westward winds during the afternoon may be enhanced in the auroral latitudes before the initial time of a storm main phase

lateral variations in mantle pvelocity from tectonically regionalized tau estimates summary estimates of tau functions for a tectonically regionalized earth are obtained from over 1 25 million seismic ray paths of isc bulletin data to study the correlation of potential lateral variations in mantle p wave velocities with recognized surface heterogeneity the use of regionalized travel time data relies on statistical regularity criteria to check the consistency of the global regionalization estimates of tau perturbations attributed to velocity structure at the seismic source and receiver regions are derived by a simple algebraic formulation contributions from near surface heterogeneity are thereby removed and permit the assessment of lateral velocity variations at depth estimates of single region equivalent tau functions are constructed and inverted to obtain velocity depth functions and extremal bounds at the 99 9 per cent confidence level for seven different tectonic regions deviations from a regionally weighted reference mean velocity function which agrees well with prem dziewonski anderson indicate significant differences particularly between oceanic and continental tectonic regions extending to a depth of 700 km p wave velocity anomalies are typically less than 1 per cent of the reference velocity the age dependence of the shallow oceanic mantle is observed by increased velocities from young 25 myr to old 100 myr regions and similarly from orogenic zones and magmatic belts to stable continental regions unlike for young and old oceanic regions stable continental regions do not show a pronounced gradient in the mean velocity residuals above 250 km continental platforms and particularly shields however show a compensation in the sign of the mean velocity residual at depths between about 350 and 700 km evidence for a velocity anomaly between 700 and 950 km is indicated significant negative residuals are observed centred at a depth of about 780 km below oceanic ridges and about 880 km below active continental regions this anomaly may be related to a boundary layer between the upper and lower mantle the level of velocity variations decreases below 950 km lateral variations are also suggested within 250 km of the core boundary

tomographic images of a mantle circulation model sampling convection in the earth s mantle by seismic tomography is difficult as evidenced by the uneven distribution of seismic stations and events with some regions being well imaged compared to others here we quantitatively explore tomographic filtering on earth structure by tracing isc p body wave data through a computer simulation of mantle circulation which accounts for internal heating of the mantle by radioactive decay heatflux from the core a depthwise increase in viscosity and plate motion history of the past 120 million years the travel time residuals are inverted by solving jointly for structure and hypocentral parameters with explicit damping and smoothing we recover the farallon and tethys slabs as well as some low velocity anomalies associated with hot upwelling flow suggesting that tomographic filtering is probably minor in areas of high ray density

alternatives to core mantle boundary topography abstract nuclear explosions at the french test sites in the south pacific have been recorded at the regional seismic networks in the western united states a total of approximately 600 good quality short period seismograms were selected from an initial set of 900 the dense receiver spacing particularly in california allows the division of the networks into numerous subarrays and the data from each subarray can be analysed using conventional array techniques such as beam forming and frequency wave number analysis the seismic rays provide dense sampling of a small area of the core mantle boundary cmb beneath the eastern pacific from 5 to 13 n and 133 to 126 w pcp has a shallow incidence angle on the cmb at an epicentral distance of 65 and d is sampled over a large swathe from 2 s to 24 n and from 134 to 123 w beam traces have been formed for the p and pcp phases for each of the subarrays using slowness and azimuth values derived from array methods good quality beams have been selected for further analysis by applying a matched filter to the beamed traces an accurate set of pcp p differential travel times has been determined and compared with iasp91 the residuals show a smooth trend over the area sampled for the given epicentral distances p and pcp have similar paths through the crust and upper mantle so we make the assumption that near source and near receiver structures have negligible effect on the differential times we also assume that the midmantle is relatively homogenous many previous studies have interpreted pcp p residuals in terms of cmb topography by mapping the residuals directly to topography a range in elevation of 40 km over a lateral extent of about 700 km results alternatively we attempted to interpret the residuals in terms of velocity heterogeneity in d a range of d models have been tested including lateral velocity variation in a d layer with constant thickness the pcp p residuals may be explained by allowing the p wave velocity to vary laterally by a factor of 2 over the region sampled with most of the region being marginally fast this suggests that d heterogeneity has large spectral power at relatively short wavelengths in this scenario previous tomographic inversions for cmb topography will have large errors since in these inversions corrections for d structure are based on low order spherical harmonic models

interpretation of airborne electromagnetic data using the modified image method the modified image method is used to invert active electromagnetic aem data from a 1984 u s navy survey of cape cod bay the high frequency data 7200 hz give a robust value for the altitude of the helicopter towed aem bird and for the first layer skin depth and hence for the first layer conductivity the inversion of low frequency 385 hz bottom probing signals produces more noise sensitive estimates for the water depth and for the conductivity contrast k the ratio of the bottom to water conductivities the results show good agreement with ground truth radar altimeter sea conductivity and sonar depth data to demonstrate the accuracy of the modified image method of inversion we incorporate ground truth measurements along a flight line and the experimental frequencies in a forward sommerfeld calculation to generate synthetic data which then are inverted using this technique

longitudinal variations in the f region ionosphere and the topside ionosphere plasmasphere observations and model simulations 1 constellation observing system for meteorology ionosphere and climate cosmic observations of the total electron content tec above and below 800 km are used to study the local time and seasonal variation of longitude structures in both the f region ionosphere as well as the topside ionosphere and plasmasphere the cosmic observations reveal the presence of distinct longitude variations in the topside ionosphere plasmasphere tec and these further exhibit a seasonal and local time dependence the predominant feature observed at all local times in the topside ionosphere plasmasphere tec is a substantial maximum minimum during northern hemisphere winter summer around 300 360 geographic longitude around equinox at a fixed local time a wave 4 variation in longitude prevails in the daytime f region tec as well as the topside ionosphere plasmasphere tec the wave 4 variation in longitude persists into the nighttime in the f region however the nighttime topside ionosphere plasmasphere tec exhibits two maxima in longitude the cosmic observations clearly reveal the presence of substantial longitude variations in the f region and topside ionosphere plasmasphere and to elucidate the source of the longitude variations results are presented based on the coupling between the global ionosphere plasmasphere model and the thermosphere ionosphere electrodynamics general circulation model the model simulations demonstrate that the orientation of the geomagnetic field plays a fundamental role in generating significant longitude variations in the topside ionosphere plasmasphere but does not considerably influence longitude variations in the f region ionosphere the model results further confirm that nonmigrating tides are the primary mechanism for generating longitude variations in the f region ionosphere the coupled model additionally demonstrates that nonmigrating tides are also of considerable importance for the generation of longitude variations in the topside ionosphere plasmasphere tec

diurnal nonmigrating tides from timed doppler interferometer wind data monthly climatologies and seasonal variations 1 timed doppler interferometer tidi measurements of zonal and meridional winds in the mesosphere lower thermosphere are analyzed for diurnal nonmigrating tides june 2002 to june 2005 climatologies of monthly mean amplitudes and phases for seven tidal components are presented at altitudes between 85 and 105 km and latitudes between 45 s and 45 n westward propagating wave numbers 2 3 and 4 the standing diurnal tide and eastward propagating wave numbers 1 2 and 3 the observed seasonal variations agree well with 1991 1994 uars results at 95 km comparisons between the tidi results and global scale wave model gswm and thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm tidal predictions indicate that the large eastward propagating wave number 3 amplitude is driven by tropical tropospheric latent heat release alone in contrast latent heating and planetary wave migrating tidal interactions are equally important to westward 2 and standing diurnal tidal forcing there is good quantitative agreement between tidi and the model predictions during equinox but the latter tend to underestimate the westward 2 and standing diurnal tide during solstice neither model reproduces the observed seasonal variations of the eastward propagating components

direct observation of the f region dynamo currents and the spatial structure of the eej by champ 1 the satellite champ in its low altitude polar orbit and with its high resolution magnetic field measurements provides the opportunity to investigate ionospheric currents in great detail in this study we focus on average features of equatorial current systems during day time considering quiet time observations from the period aug 2000 to oct 2004 we determined the mean spatial structure of the eej current the existence of reverse currents at the flanks of the primary eastward current is confirmed more importantly average characteristics of the f region dynamo driven currents are observed for the first time throughout the daytime the meridional current system driven by westward thermospheric winds peaks around noon similar meridional currents but flowing in the opposite sense are observed at the dusk sector at champ altitudes we find over the dip equator in the f region a vertical sheet current of about 6 ma m oriented downward at noon and an upward current of 4 ma m around sunset

an investigation of seawater and sediment depth using a prototype airborne electromagnetic instrumentation system a case study in broken bay australia previous studies using commercial airborne electromagnetic equipment that is not optimized for marine surveying have demonstrated the use of airborne electromagnetic methods for measuring water depth and estimating sediment thickness a new prototype helicopter time domain airborne electromagnetic system seatem 0 is now under development for bathymetric surveying the first sea trial of the seatem 0 system took place over broken bay new south wales australia in shallow water up to 30 m in depth broken bay was chosen because the separate paleodrainage systems for the hawkesbury river brisbane water and pittwater which join in broken bay give rise to paleovalleys infilled with unconsolidated sediments ranging in thickness between 0 m bedrock outcrop and 200 m the survey area also included a tombolo with a beach either side which provided the opportunity to measure water depth through a surf zone sediment thickness and water depth is predicted from stitched layered earth inversion of data based on a simplified two layer model that represents seawater and sediment overlying a resistive half space basement bedrock the resulting bathymetric profiles show agreement typically to within 1 m and 0 5 m with known water depths in areas less than 20 and 6 m deep respectively the inverted depth profile of the second sediment layer is noisy however the profiles reveal coarse topographic features of paleovalleys to depth limits of 60 to 80 m below sea level in 20 to 30 m water depth as well as resolving bedrock ridges and exposed reefs in shallow waters

seasonal and longitudinal variations of the solar quiet sq current system during solar minimum determined by champ satellite magnetic field observations 1 vector magnetometer observations from the challenging minisatellite payload champ satellite are used to determine the solar quiet sq current system during the recent solar minimum observations from 2006 to 2008 are combined and after removal of a main field model and accounting for field aligned currents the longitudinal and seasonal variation of the sq currents are determined through the method of spherical harmonic analysis comparison with sq currents derived from ground based magnetometers in the african european longitude sector reveals similar amplitudes and seasonal variations indicating that the champ observations can reliably determine the sq current system the seasonal variation is consistent with prior observations during solar minimum conditions and in the northern hemisphere exhibits a primarily annual variation with peak currents during local summer the seasonal variation in the southern hemisphere is characterized by a semiannual variation with the maxima occurring around the equinoxes significant longitudinal variations are also observed and they display a seasonal variability during northern hemisphere summer the predominant feature at local noon is a wave number 1 variation in longitude during the remainder of the year a wave 3 longitudinal structure is observed at this local time the longitudinal variations are considered to be due to a combination of the orientation and strength of the geomagnetic field as well as the tidal winds in the lower thermosphere variations in tidal winds due to nonmigrating tides may influence the dynamo generated electric fields and currents resulting in the observed longitudinal variations of the sq current function

nonmigrating diurnal tides observed in global thermospheric winds 1 nonmigrating diurnal tides between 90 and 270 km are inferred from upper atmosphere research satellite uars wind imaging interferometer windii winds this study represents the first known effort to directly analyze tidal wave number structure and propagation direction in winds observed over this altitude range prominent diurnal tides include an eastward propagating wave number 3 a zonally symmetric tide and a westward propagating wave number 2 uars high resolution doppler imager winds between 60 and 100 km were analyzed identically and show excellent consistency with windii tides observed tides were compared with tidal fits to hough mode extensions windii tides are generally damped more slowly above 120 km than fitted tides and the zonally symmetric tide indicates a thermospheric source not captured by hough mode extensions our study provides additional confirmation that tides act as direct coupling agents between the troposphere and the thermosphere and f region in addition to their role in the e region dynamo

airborne electromagnetic bathymetry airborne electromagnetic techniques provide an efficient means for determining the bathymetry of shallow seas and coastal regions offshore time domain data collected with the input system may be interpreted quickly and inexpensively using the simple table look up algorithm described here this interpretation algorithm is based on two dimensionless parameters which depend on the six channel amplitudes of the recorded input data these amplitudes are computed and tabulated for a suite of simple two layer models in which seawater depth is the only variable quantity the experimental data can then be interpreted by comparison with the tables of theoretical values to obtain the bathymetry beneath the flight path the inversion algorithm has proven accurate and stable in the range of 0 40 m of seawater the representative difference between the interpreted depths and the charted depths is about 2 m bottom gradients lower than 5 percent were resolved accurately beneath 0 25 m of water independent interpreta

longitudinal variation of the e region electric fields caused by atmospheric tides 1 polarization electric fields created by the e and f region dynamos cause the uplift of f region plasma the subsequent redistribution of that plasma along the magnetic field lines creates the equatorial ionospheric anomaly eia observations of the post sunset eia made by the image and timed satellites are compared here with champ orsted and sac c observations of the noontime equatorial electrojet eej during magnetically quiet periods around equinox the eia and eej show a remarkably similar four peaked wave like longitudinal variation its structure is consistent with the longitudinal variation in the strength of diurnal tides that drive the e region dynamo this indicates a strong vertical coupling between the ionosphere and troposphere because the four peaked tidal structure is driven by tropospheric weather furthermore the dayside ionospheric conditions are found to perform the global scale longitudinal structure of the post sunset ionosphere at low latitudes

nonmigrating diurnal tides in mesospheric and lower thermospheric winds and temperatures abstract this paper presents analyses of nonmigrating diurnal tide signatures in high resolution doppler imager mesospheric and lower thermospheric winds and temperatures a global comparison of both winds and temperature reveals equatorial features corresponding to nonmigrating tides structures interpreted as zonal mean and eastward nonmigrating diurnal tides display consistency between horizontal winds and temperatures the second symmetric mode is prominent in the zonal mean and wavenumber 1 the gravest antisymmetric mode and the gravest symmetric or kelvin mode are the main features in zonal wavenumbers 2 and 3 the amplitudes of the tides generally increase with altitude and maximize within 90 110 km

tidal variability in the ionospheric dynamo region 1 the seasonal and interannual variability of migrating sun synchronous and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the saber instrument on the timed spacecraft during 2002 2006 quasi biennial variations of order 10 15 in migrating diurnal and semidiurnal tidal amplitudes are found presumably due to modulation by the quasi biennial oscillation qbo as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere a number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields the most prominent of these i e those that appear at amplitudes of order 5 10 k in a 5 year mean climatology include the zonally symmetric s 0 diurnal tide d0 the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s 2 de2 and se2 and s 3 de3 and se3 and the following westward propagating waves diurnal s 2 dw2 semidiurnal s 1 sw1 s 3 sw3 and s 4 sw4 and terdiurnal s 5 tw5 these waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s 1 or s 2 or by longitudinal variations of tropospheric thermal forcing additional waves that occur during some years or undergo phase cancellation within construction of a 5 year climatology include dw5 se1 se4 sw6 te1 tw1 and tw7 it is anticipated that the winds that accompany all of these waves in the 100 170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities in addition to the wave 4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies the waves revealed here will generate wave 1 sw1 sw3 d0 dw2 wave 2 sw4 tw1 wave 3 de2 se1 wave 4 de3 se2 dw5 sw6 te1 tw7 wave 5 se3 and wave 6 se4 components of this ionospheric variability depending on year and time of year however the absolute and relative efficiencies with which these waves produce electric fields remains to be determined

tomographic inversion for three dimensional velocity structure at mount st helens using earthquake data tomographic inversion is applied to 17 659 p phase observations at 21 stations from 2023 earthquakes in the vicinity of mount st helens to study the three dimensional velocity structure block size for the inversion is 2 km horizontally and 2 km or more vertically locations of hypocenters are assumed known and are based on a reference one dimensional layered velocity structure a conjugate gradient technique lsqr is used to invert the large sparse system of equations augmented by regularization with a laplacian roughening matrix resolution is estimated by computing the impulse response of the inversion for various critical locations and uncertainties of the estimates are determined by a jackknife approach the results of the inversion show a remarkable correlation with known geological and geophysical features the spirit lake and spud mt plutons are characterized by high velocity regions extending to approximately 9 km depth the st helens seismic zone a band of diffuse seismicity extending nnw from the volcano is evident as a prominent low velocity lineation the change in character of the velocity anomalies south of st helens corresponds well with the near cessation of seismic activity there a low velocity anomaly beneath the crater from 6 to 16 km depths may represent modern magma accumulations

estimating fluid induced stress change from observed deformation author s vasco dw harness p pride s hoversten m abstract the authors 2016 published by oxford university press on behalf of the royal astronomical society observed deformation is sensitive to a changing stress field within the earth however there are several impediments to a direct inversion of geodetic measurements for changes in stress estimating six independent components of stress change from a smaller number of displacement or strain components is inherently non unique the reliance upon surface measurements leads to a loss of resolution due to the attenuation of higher spatial frequencies in the displacement field with distance from a source we adopt a technique suited to the estimation of stress changes due to the injection and or withdrawal of fluids at depth in this approach the surface displacement data provides an estimate of the volume change responsible for the deformation rather than stress changes themselves the inversion for volume change is constrained by the fluid fluxes into and out of the reservoir the distribution of volume change is used to calculate the displacements in the region above the reservoir estimates of stress change follow from differentiating the displacement field in conjunction with a geomechanical model of the overburden we apply the technique to interferometric synthetic aperture radar insar observations gathered over a petroleum reservoir in the san joaquin valley of california an analysis of the insar range changes reveals that the stress field in the overburden varies rapidly both in space and in time the inferred stress variations are found to be compatible with the documented failure of a well in the field

time gcm study of the ionospheric equatorial vertical drift changes during the 2006 stratospheric sudden warming this modeling study quantifies the daytime low latitude vertical e b drift changes in the longitudinal wave number 1 wn1 to wn4 during the major extended january 2006 stratospheric sudden warming ssw period as simulated by the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and attributes the drift changes to specific tides and planetary waves pws the largest drift amplitude change approximately 5 m s is seen in wn1 with a strong temporal correlation to the ssw the wn1 drift is primarily caused by the semidiurnal westward propagating tide with zonal wave number 1 sw1 and secondarily by a stationary planetary wave with zonal wave number 1 pw1 sw1 is generated by the nonlinear interaction of pw1 and the migrating semidiurnal tide sw2 at high latitude around 90 100 km the simulations suggest that the e region pw1 around 100 130 km at the different latitudes has different origins at high latitudes the pw1 is related to the original stratospheric pw1 at midlatitudes the model indicates pw1 is due to the nonlinear interaction of sw1 and sw2 around 95 105 km and at low latitudes the pw1 might be caused by the nonlinear interaction between de2 and de3 the time evolution of the simulated wn4 in the vertical e b drift amplitude shows no temporal correlation with the ssw the wn4 in the low latitude vertical drift is attributed to the diurnal eastward propagating tide with zonal wave number 3 de3 and the contributions from se2 te1 and pw4 are negligible

global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide 1 migrating tide 1 using the timed doppler interferometer tidi mesospheric and lower thermospheric neutral wind multiyear data set 2002 2007 and ncar time general circulation models gcm 1 2 annual run results 2002 2005 at the tidi sampling points we study the migrating diurnal tide s global distribution interannual and seasonal variations in connection with the mean zonal wind interannual variations a strong quasi biennial oscillation qbo effect on the diurnal tide was observed in the tidi data and reproduced to a lesser degree in the time gcm run the migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric qbo and weaker during the westward phase westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric qbo in 2002 2004 and 2006 the strongest qbo effect on both the migrating diurnal tide and mean zonal winds was observed during the march equinox the stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric qbo the tidi data also exhibit large interhemispheric asymmetry the westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide the time gcm 1 2 diurnal tide amplitudes are in general smaller than those observed by the tidi instrument limited vertical spatial resolution for the time cgm 1 2 is suggested as the cause future improvements are expected with a higher spatial resolution in the model

direct observations of nonmigrating diurnal tides in the equatorial thermosphere 1 we present direct observations of nonmigrating diurnal tides in the 90 270 km range inferred from the upper atmosphere research satellite uars wind imaging interferometer windii a prominent zonal wavenumber 4 appears in daytime zonal winds extending to 180 km we interpret this signature as an eastward propagating diurnal wavenumber 3 de3 viewed from the satellite perspective this evidence of the extended upward propagation of de3 demonstrates that it acts as a direct coupling agent between the troposphere and the thermosphere and f region in addition to its role in the e region dynamo

robust inversion of iasp91 travel time residuals for mantle p and s velocity structure earthquake mislocations and station corrections using both p and s arrival time information 41 108 events in the international seismological centre isc catalog for the years 1964 to 1987 are relocated relative to the iasp91 velocity model the mean absolute horizontal relocation is 7 7 km and the mean absolute depth relocation is 9 1 km the mean absolute origin time shift is 1 2 s the relocation procedure increased the p residual standard deviation slightly from 2 3 s to 2 5 s while decreasing the s residual standard deviation from 6 8 s to 6 1 s when plotted as bottoming point averages the resulting iasp91 p and s arrival time residuals show coherent patterns as a function of geographic location an iterative lp residual norm minimization algorithm is used to estimate the set of p and s velocity variations as well as the earthquake relocation and seismographic station parameters which best explain the travel time residuals the procedure is robust in that extremely large travel time residuals which are common in the isc data do not unduly influence the velocity estimates both the p and s models of lateral heterogeneity contain prominent circum pacific low velocities 1 to 2 perturbations underlying the back arc basins between 35 and 200 km depth this ring of negative deviations continues into the depth interval 200 400 km the continental cratons are underlain by high velocity anomalies with maximum amplitudes of 2 iceland and the azores are underlain by low velocity mantle material that extends down to at least 400 km the benioff zones are only intermittently imaged as 1 2 high velocity regions in the uppermost 400 km they are best resolved in the p velocity variations both the p and s velocity models contain a circum pacific ring beneath the benioff zones of 1 2 positive velocity deviations in the depth range 660 870 km coherent high velocity features are seen below south america borneo tonga fiji the marianas and the northern kuriles the anomalies beneath south america and borneo extend into the 870 1070 km depth range below depths of 1270 km for p variations and 1070 km for s variations the amplitude of the heterogeneity has decreased significantly it is only in the lowermost mantle 2670 km to the core mantle boundary that the level of p heterogeneity rises significantly above the estimated noise level in this depth range a partial ring around the pacific basin is observed although this

connections between deep tropical clouds and the earth s ionosphere 1 we report on a series of simulations with the national center for atmospheric research ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm which were designed to replicate and facilitate the interpretation of the longitudinal structure discovered in image satellite airglow observations of the equatorial ionization anomaly eia at the far ultraviolet fuv 135 6 nm wavelength during march april 2002 equinox our time gcm results indicate that the four peaked longitudinal variation in the eia observed by image fuv near 20 00 local solar time can be explained by the effects of an eastward propagating zonal wavenumber 3 diurnal tide de3 that is excited by latent heat release associated with raindrop formation in the tropical troposphere

whole mantle p wave travel time tomography abstract a method of tomographic inversion to obtain three dimensional velocity perturbations in the earth s whole mantle has been developed and applied to more than two million p wave arrival time data reported by international seismology center isc the model is parameterized with 32 768 blocks the divisions in latitude longitude and radius are 32 64 and 16 respectively horizontal cell size is 5 6 5 6 the layer thicknesses vary with depth 29 km just below the surface and 334 km just above the core mantle boundary starting from a spherically symmetric earth model we obtained a three dimensional model using the following iterative procedures first we relocated all the events second we backprojected the residual into the whole mantle third we refined the spherically symmetric earth model the solutions have been converged in five iterations we adopted the following techniques in the backprojection procedure the first order smoothness was introduced as a damping which makes the solution independent of the starting model and its apparent fluctuation minimal the basic equations for delay times and smoothness are solved using the conjugate gradient method an iterative method which guarantees the convergence of solution into the exact least squares solution the weight on the smoothness i e the damping factor was objectively determined by a simplified cross validation technique the final solution was obtained as an average of the ten solutions each of which was derived from one tenth of the total data set the reliability of the solution is examined in two ways 1 mapping the resolution given by the reconstruction of checkerboard patterns and 2 mapping the variance given from the gaussian noise input this is the first result which delineates the whole mantle structure with its reliability mapping the longest wavelength anomalies of the lower mantle are similar to those of previous studies by dziewonski 1984 and hager and clayton 1989 however the shorter wavelength patterns have many discrepancies the fast anomalies of the uppermost mantle beneath the shield and the slow anomalies beneath the active tectonic regions are clearly seen we also revealed the l 2 pattern at the transition zone reported by the previous surface wave and free oscillation studies the most striking feature is that of the fast anomalies lying along the extension of the large subducting plate up to depths of about 1000 km or more the resolving powers in these regions are generally good

what patterns of heterogeneity in the earth s mantle can be revealed by seismic travel time tomography abstract we investigate which patterns of seismic heterogeneity in the mantle would be returned reliably by a tomographic inversion in which the model mantle is parametrized by a set of discrete non overlapping voxels we construct synthetic data sets based on real ray sampling of the mantle by introducing spherical harmonic patterns of velocity heterogeneity and perform inversions of the synthetic data we expand the resulting voxel model in spherical harmonics and compare the power at each degree and in each model layer with the input spherical harmonics in order to determine which patterns produced by inversions of real data may be deemed reliable and to identify patterns which must be viewed with skepticism we find that while the power input to a particular pattern of heterogeneity in the 0 200 km layer is generally recovered accurately the pattern itself is poorly determined in this layer a pattern in the 200 400 km layer is more precisely determined though the power contained in the pattern is consistently underestimated and more leakage occurs to the layers above and below the transition zone 400 670 km shows similarly strong control of lateral heterogeneity patterns but tests return a more accurate estimate of input powre than for the second layer the l 2 4 and 6 components all show accurate recovery in the 400 670 km layer this result supports previous findings from inversions with real data that l 2 is a significant pattern of heterogeneity in the mantle s transition zone and that l 4 is not a significant pattern for the entire upper mantle l 6 would be retrieved reliably and its constructive behavior in upper mantle models derived with real data is confirmed these tests also demonstrate the inability of our inversion procedure to retrieve shorter wavelength features in the lower mantle the results for our lowermost layer d must be considered suspect due to the inadequate constraints placed on model values by our ray coverage and the sensitivity of these results to noise in the data

tropospheric tidal effects on the middle and upper atmosphere 1 numerical experiments that explore the effects of tides of tropospheric origin on the upper and middle atmosphere reveal strong signatures of an eastward propagating zonal wave number 3 diurnal tide de3 which peaks near 110 km and penetrates into the upper thermosphere we demonstrate that nonmigrating tidal dissipation dominated by de3 effects in the upper mesosphere and lower thermosphere mlt strongly accelerates the zonal mean wind field affecting both the altitude and magnitude of the low latitude jets we also quantify for the first time a stationary planetary wave 4 oscillation spw4 in the mlt which is excited by nonlinear interaction between the de3 and the migrating diurnal tide dw1 our results suggest that the spw4 modulates the de3 mlt response and may impact the e region dynamo as well as ionospheric and thermospheric signatures at much higher altitudes

longitudinal variations in the equatorial vertical drift in the topside ionosphere 1 the vertical ion drift is important for understanding and modeling the electrodynamics at low latitudes measurements from the ion drift meter on the defense meteorological satellite program dmsp f15 are used to examine longitudinal variations in the vertical ion drift at the dip equator in the topside ionosphere local time was restricted to 0930 and the data were organized by month for 2001 and 2002 two features were found contributing to the longitudinal variations in the electrodynamics meridional winds contribute to the equatorial vertical ion drift at the 830 km magnetic apex due to their dynamo action at the foot points of the magnetic field lines in the f region at magnetic latitudes near 15 electric fields producing a downward perturbation drift at 0930 are produced by hemispheric differences in the dynamo current due primarily to the different orientation of the magnetic meridian relative to the terminator this produces the seasonally dependent variation as a function of longitude that is observed a wavenumber 4 longitudinal variation also appears to be present throughout the year but is more influential during equinox conditions this variation also shows a seasonal cycle shifting east during northern summer and west during northern winter further analysis would be required to isolate the characteristics of a wavenumber 4 driver from the wavenumber 4 component of the fourier series used here to fit the data

tomographic inversions for mantle p wave velocity structure based on the minimization of l 2 and l 1 norms of international seismological centre travel time residuals we use international seismological centre isc p arrival data 1964 1987 and iterative algorithms which minimize the l1 and l2 residual norms to solve simultaneously for three dimensional p velocity variations in earth s mantle source mislocations and station corrections we find that the maximum velocity perturbations produced by the l1 minimization approximately 4 in our final model are relatively insensitive to smoothing and damping constraints therefore using an l1 norm criterion allows us to keep the bias introduced to the inversion to a minimum among the well resolved features contained in both the l1 and the l2 velocity models are a fast anomaly in the lower mantle beneath the tonga new hebrides subduction zone to a depth of 1670 km and another fast anomaly beneath the japanese island arc and eastern asia continuity between these anomalies and shallower fast anomalies is not clear a fast anomaly extending from 670 km to 2070 km depth appears beneath eastern north america the caribbean and north central south america a broad fast anomaly appears beneath eastern asia just above the core mantle boundary as well as several slow anomalies under the pacific basin of comparable size both models contain a circum pacific ring of 2 lower velocities in the depth range 0 200 km associated with back arc basins high velocities over 2 associated with the continental shields tend to disappear below 400 km though a significant region of high velocity remains beneath the siberian platform in the 400 to 670 km depth interval

troposphere thermosphere tidal coupling as measured by the saber instrument on timed during july september 2002 1 coupling between the troposphere and lower thermosphere due to upward propagating tides is investigated using temperatures measured from the saber instrument on the timed satellite the data analyzed here are confined to 20 120 km altitude and 40 latitude during 20 july to 20 september 2002 apart from the migrating sun synchronous tidal components the predominant feature seen from the satellite frame during this period is a wave 4 structure in longitude with extrema of up to 40 50 k at 110 km amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time and as the wave s responsible for this structure vary with time the primary wave responsible for the wave 4 pattern is the eastward propagating diurnal tide with zonal wave number s 3 de3 its average amplitude distribution over the interval is quasi symmetric about the equator similar to that of a kelvin wave with maximum of about 20 k at 5 s and 110 km de3 is primarily excited by latent heating due to deep tropical convection in the troposphere it is demonstrated that existence of de3 is intimately connected with the predominant wave 4 longitude distribution of topography and land sea difference at low latitudes and an analogy is drawn with the strong presence of de1 in mars atmosphere the predominant wave 2 topography on mars and the wave 2 patterns that dominate density measurements from the mars global surveyor mgs spacecraft near 130 km additional diurnal semidiurnal and terdiurnal nonmigrating tides are also revealed in the present study these tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s 1 known to exist in the southern hemisphere during this period just prior to the austral midwinter stratospheric warming of 2002

longitudinal variation in global navigation satellite systems tec and topside ion density over south american sector associated with the four peaked wave structures 1 recent observations of the low latitude ionospheric electron density revealed a four peaked longitudinal structure in the equatorial ionization anomaly when plotted at a constant local time frame it was proposed that neutral wind driven e region dynamo electric fields due to nonmigrating tidal modes are responsible for this pattern we examine the four peaked structure in the observed topside ion density and its manifestation as longitudinal structures in total electron content tec over south america the strong longitudinal variation in tec characterized by larger value over brazilian eastern longitude sector as compared to that over the peruvian western longitude is modeled using the sheffield university plasmasphere ionosphere model supim aiming to identify the control factors responsible for the longitude variation we found that the supim runs using as input the existing standard models of vertical drift and thermospheric winds do not explain the tec longitudinal structure realistic values of these control parameters were generated based on the strong vertical drift longitudinal variation as determined from magnetometer and digisonde data and appropriately adjusted winds horizontal wind model these realistic vertical drifts together with the modified thermospheric wind when used as input to the supim are found to satisfactorily explain the longitudinal differences in the tec and topside ion density ni over south america the study shows that the tec in the whole latitude distribution is larger over the east coast than over the west coast of south america and that the vertical drift and thermospheirc winds control the longitudinal four wave structure in the tec and ni

testing the limits of aem bathymetry with a floating tem system a floating transient electromagnetic tem system sea ring simulating a low altitude helicopter airborne electromagnetic aem system was constructed to test the accuracy of the aem method for measuring water depth and estimating sediment thickness in shallow coastal waters a square transmitter loop 10 10 m plus concentric inner and outer receiver loops was strung from masts supported by the circular sea ring base data were stacked over periods from 1 to approximately 60 s and with loop heights ranging between approximately 5 5 and 12 m above sea level the towed sea ring provides a stable platform at a known fixed altitude in calm waters we have undertaken modeling to investigate the effect of vertical and horizontal displacements of the loops and to compare circular and square loopgeometries in proximity to the sea surface with relatively long stacking times as long as approximately 60 s the uncertainty in altitude can be reduced to very low levels the sea ring has been deployed near

improved seawater depth determination using corrected helicopter time domain electromagnetic data abstract two areas within sydney harbour were surveyed in 2002 with a helicopter borne time domain electromagnetic system to test its potential for bathymetric mapping in shallow seawater as delivered the data were improperly calibrated therefore a re calibration was performed to reconcile the measured data with ground truth synthetic electromagnetic transients were computed for two layer models representing the seawater and the sediment overlying bedrock at a number of locations within the survey area the seawater depth in the models varied between 3 m and 70 m the measured and calculated data were compared at each delay time and were found to be linearly related the slope and intercept of the line of best fit were used to correct all the measured data inversion of the corrected time domain electromagnetic data generally resolved the bathymetry to submetre accuracy down to depths of about 55 m

importance of the reference model in linearized tomography and images of subduction below the caribbean plate in linearized delay time tomography the choice of a one dimensional reference model is very important for correct mapping of seismic anomalies we demonstrate that the use of an inadequate background model results in artifacts in tomographic images which may give rise to erroneous interpretations particularly the absence or presence of upper mantle discontinuities in the reference model influences the mapping of structures e g subducting slabs at the transition between upper and lower mantle new tomographic images of the mantle below the caribbean region are presented these show the extent of the lesser antilles subduction zone down to 600 km which is well below the seismic zone a high velocity anomaly is imaged from the mid american trench to lower mantle depths 1400 km

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

comparison of champ and time gcm nonmigrating tidal signals in the thermospheric zonal wind 1 four years 2002 2005 of continuous accelerometer measurements taken onboard the champ satellite orbit altitude 400 km offer a unique opportunity to investigate the thermospheric zonal wind on a global scale recently we were able to relate the longitudinal wave 4 structure in the zonal wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with zonal wave number 3 de3 the de3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds in order to investigate the mechanisms that couple the tidal signals to the upper thermosphere we undertook a comparison with the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm developed at the national center for atmospheric research ncar we ran the model for a day in march june september and december and applied the same processing steps to the model output as was done for the champ tidal analysis the main results of the comparison can be summarized as follows 1 time gcm simulations do not correctly reproduce the observed intra annual variations of de3 and the eastward propagating diurnal tide with zonal wave number 2 de2 2 simulations of de3 for june are more successful both time gcm and champ show an increase in de3 amplitudes with decreasing solar flux level 3 the amplitudes of the simulated westward propagating diurnal tide with zonal wave number 2 dw2 and the standing diurnal tide d0 increase with increasing solar flux in june the predicted dependence of dw2 and do on solar flux is also observed by champ

climatology of upward propagating diurnal and semidiurnal tides in the thermosphere 1 a major challenge in delineating and understanding the space weather of the ionosphere thermosphere system is the lack of global tidal observations in the 120 400 km thermospheric gap between satellite remote sensing and in situ tidal diagnostics this paper aims to close this gap by presenting an observation based climatological tidal model of the thermosphere ctmt of self consistent upward propagating migrating and nonmigrating diurnal and semidiurnal tides from 80 400 km and pole to pole for moderate f10 7 110 sfu solar flux conditions ctmt includes the 6 8 most important diurnal semidiurnal tidal components for temperature density and zonal meridional and vertical winds and is based on hough mode extension fits to 2002 2008 mean timed satellite tidal diagnostics in the mesosphere lower thermosphere mlt validation with independent 2002 2008 champ tidal diagnostics f10 7 105 sfu around 400 km proves that the approach captures nonmigrating tides well indicating that these waves propagate directly upward without significant tidal forcing occurring in the thermosphere notable exceptions are the dw2 and d0 components that are most likely generated in situ by nonlinear interaction forcing in the upper thermosphere ctmt is suitable for driving upper atmosphere models that require self consistent tidal fields in the mlt region as a lower boundary condition it does not include migrating tides due to in situ euv absorption in the upper thermosphere but allows us to quantitatively assess thermospheric variability due to tides from the lower atmosphere this is done by discussing longitude latitude maps of reconstructed diurnal and semidiurnal tidal variations as function of altitude and local time

sources of low latitude ionospheric e b drifts and their variability 1 the complete mechanism of how upward propagating tropospheric tides connect to the upper atmosphere is not yet fully understood one proposed mechanism is via ionospheric wind dynamo however other sources can potentially alter the vertical e b drift gravity and plasma pressure gradient driven current the geomagnetic main field and longitudinal variation in the conductivities in this study we examine the contribution to the vertical drift from these sources and compare them we use march equinox results from the thermosphere ionosphere mesosphere electrodynamics general circulation model we found that the gravity and plasma pressure gradient driven current and the longitudinal variation of the conductivities excluding the variation due to the geomagnetic main field do not change the longitudinal variation of the vertical drift significantly modifying the geomagnetic main field will change the vertical drift at 5 6 lt 18 19 lt and 23 24 lt at almost all longitudes in general the influence of the geomagnetic main field on the vertical drift is larger with respect to the maximum difference at 18 19 lt and 23 24 lt equal at 5 6 lt and smaller at 14 15 lt than the influence due to nonmigrating tidal components in the neutral winds examination of the contribution from e and f region neutral winds to the vertical drift shows that their importance depends on the local time and the solar activity this implies that the vertical drift has to be analyzed at specific local times to examine the relation between the wave number in the vertical drift and in the neutral winds

mim and nonlinear least squares inversions of aem data in barataria basin louisiana an airborne electromagnetic survey was performed over the marsh and estuarine waters of the barataria basin of louisiana two inversion methods were applied to the measured data to calculate layer thicknesses and conductivities the modified image method mim and a nonlinear least squares method of inversion using two two layer forward models and one three layer forward model with results generally in good agreement uniform horizontal water layers in the near shore gulf of mexico with the fresher less saline less conductive water above the saltier more saline more conductive water can be seen clearly more complex near surface layering showing decreasing salinity conductivity with depth can be seen in the marshes and inland areas the first layer water depth is calculated to be 1 2 m with the second layer water depth around 4 m the first layer marsh and beach depths are computed to be 0 3 m and the second layer marsh and beach depths vary from 2 to 9 m the first layer water conductivity is ca

the earth s thermospheric superrotation from dynamics explorer 2 neutral thermospheric zonal winds measured from the wind and temperature experiment on dynamics explorer 2 have been analyzed to provide a measure of the superrotation of the neutral thermosphere the data were averaged in local time in 10 degree bands from the equator to 40 degrees latitude the results show an average wind velocity on the order of 18 m s to the east at the equator and a westward wind of the same magnitude at mid latitudes within the range of altitudes of the data base 200 to 700 km no evidence of any significant altitude dependence was found averaging our data over the latitude bands studied indicates a net corotation of the thermosphere this result is not in agreement with the superrotation value reported by king hele and walker on the basis of satellite drag analysis

two dimensional mapping of sea ice keels with airborne electromagnetics airborne electromagnetic aem equipment can be used to sense sea ice thickness by interpreting the aem data to obtain the distance from the towed bird that holds the em system to the ice seawater interface the ice thickness itself is obtained by subtracting from that quantity the distance from the bird to the upper ice surface as determined by a laser altimeter to interpret aem data acquired over sea ice keels we first solve the forward problem using an integral equation approach to the neumann boundary value problem in this approach we assume that sea ice is an insulator and that seawater is a perfect conductor when the ice keel is two dimensional the pertinent equations can be transformed into the wavenumber domain along the strike direction resulting in the rapid numerical computation of the aem response by compiling numerical model results we constructed an interpretation chart that relates the parameters of the observed aem response anomaly to the geometric variables of the ice keel the

seismic tomography of the earth s mantle the analysis of information contained in seismograms is the most promis ing tool for retrieving the three dimensional structure of the earth s mantle and thereby improving our understanding of its dynamics the procedure through which three dimensional images of different parts of the earth s interior arc obtained by inversion of a set of observables measured on the surface of the earth is commonly termed tomography by analogy with the medical procedure with which it shares many aspects of methodology but with much less favorable experimental conditions ideally one would like to be able to model entire seismograms over a wide frequency band for a large number of uniformly distributed sources and stations in order to obtain an optimal illumination of the inhomogeneities appropriate for tomographic inversion in practice a number of difficulties and limitations arise onc is the nonuniform distribution of sources and receivers seis micity is concentrated at plate boundaries and the distribution of con tinental and island areas leaves large portions of the oceans unin strumented another difficulty is our limited ability to accurately forward model the effects of wave propagation in a realistic earth which presents departures from a spherically symmetric referencc model of both elastic anc1astic and isotropic anisotropic nature this is why until now the simplest kind of tomography travel time tomography has prevailed relying on simplifying assumptions concerning the interaction of asphericity with propagating seismic waves ray theory and the laws of geometrical optics in their

longitudinal variation of f region electron density and thermospheric zonal wind caused by atmospheric tides 1 simultaneous observations of the electron density and the zonal wind obtained by the champ satellite at 400 km are used to study systematic longitudinal variations the time period selected is august september 2004 allowing observations at pre noon and post sunset hours the equatorial ionization anomaly eia and the zonal delta wind deviation from zonal average show a persistent and dominant 4 peaked longitudinal variation we interpret this structure as caused by the wavenumber 3 nonmigrating diurnal tide de3 the eia and the zonal delta wind exhibit extrema at about the same longitudes but while the intensifications of the eia and the delta wind are in phase during the evening hours they are out of phase in the morning possible coupling mechanisms are investigated

three dimensional seismic models of the earth s mantle accurate models of the distribution of elastic heterogeneity in the earth s mantle are important in many areas of geophysics the purpose of this paper is to characterize and compare quantitatively a set of recent three dimensional models of the elastic structure of the earth to assess their similarities and differences and to analyze their fit to one class of data in order to highlight fruitful directions for future research the aspherical models considered are the following m84c woodhouse and dziewonski 1984 lo2 56 dziewonski 1984 mdlsh tanimoto 1990a sh 10c 17 masters et al 1992 and s12 wm13 su et al 1994 through much of the discussion m84c and lo2 56 are combined into a single whole mantle model m84c lo2 56 the fit of each model to previously tabulated even degree normal mode structure coefficients taken from smith and masters 1989a and ritzwoller et al 1988 for multiplets along the normal mode fundamental and first second and fifth overtone branches is also presented rather than concentrating on detailed comparisons of specific features of the models analyses of these models are general and statistical in nature in particular we focus on a comparison of the amplitude and the radial and geographical distribution of heterogeneity in each model and how variations in each affect the fit to the normal mode observations in general the results of the comparisons between the models are encouraging especially with respect to the geographical distribution of heterogeneity and in the fit to the normal mode data sensitive to the upper mantle and lowermost lower mantle there remain however significant discrepancies in amplitude and in the radial distribution of heterogeneity especially near the top of the upper mantle and near the top of the lower mantle the confident use of these models to constrain compositional and dynamical information about the mantle will await the resolution of these discrepancies the factors that may be responsible for the differences in the models and or for the misfit between the observed and predicted normal mode data are divided into two types intrinsic or procedural and extrinsic or structural we discuss only three extrinsic factors at length here including errors in the reference crustal models unmodeled topography on discontinuities in the interior of the mantle and errors in the assumed relationships between shear s and compressional p heterogeneity

whole earth structure estimated from seismic arrival times the arrival times of 10 compressional and shear phases p s pp pcp ss scs pk pab pk pbc pk pdf sk sac and two sets of differential times ss s410s and ss s660s are used to infer the earth s three dimensional structure with the exception of ss sds the raw data are composed of arrival times from the international seismological centre isc catalogue the isc events have been relocated using p and s phases and the ak135 radial earth model a total of 818 655 summary arrival times constrain lateral velocity variations in the crust mantle and core we also determine relocation parameters for all events stations corrections for each phase boundary topography 410 km 660 km core mantle boundary inner core boundary and inner core anisotropy variations our model of p and s velocity variations in the crust and mantle contains the general features observed in other body wave inversions a low velocity ring around the pacific ocean basin in the depth range 35 400 km high velocity anomalies associated with subducting slabs most prominent in the depth range 660 1070 km and high velocity anomalies surrounding the pacific basin just above the core mantle boundary in the outer core there is evidence of a latitudinal variation in velocity approaching 0 6 in magnitude with lower p velocities at the poles and higher velocities near the equator this pattern is observed throughout the outer core but is most prominent in the depth range 3671 4071 km and near the inner core boundary synthetic tests indicate that outer core features are moderately resolvable and inversions of random arrival times indicates that the anomalies are a factor of 2 above the estimated parameter noise level lateral heterogeneity in the inner core trades off with anisotropy resulting in poor resolution of isotropic velocity variations anisotropy in the inner core is predominantly subparallel to the earth s axis and of the order of 3 but this value can decrease if more inner core isotropic lateral heterogeneity is allowed a comparison of structure above and below the core mantle boundary cmb indicates that velocity heterogeneity is uncorrelated across the cmb but there is a moderate correlation between cmb topograpy and outer core heterogeneity an inversion in which the pk pdf residuals were absent indicates that the latitudinal pattern of outer core velocity variations is not due to the influence of inner core velocity structure

confidence regions for mantle heterogeneity least squares tomographic models of mantle p and s velocity structure from travel times have shown large scale variations correlated with surface tectonic features as well as coherent structures in the lowermost mantle the reliability of these global features of velocity models depends on whether velocity throughout the features can be estimated well simultaneously one needs to be able to say with confidence that a feature involving many voxels is likely to be real we find a lower bound on how wide a 95 simultaneous confidence region for least squares estimates of mantle p or s velocity perturbations must be as a function of position in the mantle suppose perhaps optimistically that summary ray travel time errors are independent with mean zero and standard deviation 0 25 s for direct p phases and standard deviation 0 5 s for all other phases regardless of distance if summary travel time residuals are fitted by least squares to a mantle model parametrized by 4872 10 by 10 voxels the half width of a 95 confidence region for p velocity using 889 909 summary p rays 84 046 summary pp rays 67 228 summary pp rays 23 024 summary pcp rays 11 239 summary pkpab rays 47 227 summary pkpbc rays and 141 843 summary pkpdf rays ranges from 0 025 to 99 8 km s 1 it is wider than 0 193 km s 1 in half of the mantle and wider than 0 593 km s 1 in a quarter of the mantle by volume under the same assumptions and using the same parametrization a 95 confidence region for s velocity based on 163 354 summary s rays 13 781 summary ss rays 7441 summary scs rays and 12 494 summary ss rays ranges from 0 031 to km s 1 is wider than 0 254 km s 1 in half of the mantle and is wider than 0 554 km s 1 in a quarter of the mantle with this ray set parametrization and error model the 95 confidence region around the least squares estimate of p velocity includes the radially symmetric iasp91 model for 86 6 of the mantle s volume a 95 confidence region around the least squares s estimate includes iasp91 for 88 9 of the mantle s volume on a global scale the mantle s velocity structure is nearly consistent with the iasp91 radially symmetric model smaller voxels more realistic assumptions about the errors more accurate modeling of the physics and three dimensional structure outside the mantle would make the confidence regions still wider

review of electromagnetic induction for mapping barrier island framework geology abstract the geologic framework controls on modern barrier island transgression and the relationship of these controls to subsurface structure hydrology and island geomorphology are not well understood recent evidence suggests that alongshore variations in pre holocene geology of barrier islands modify nearshore hydrodynamic processes and sediment transport ultimately affecting how barrier islands will respond to relative sea level rise explorations of holocene barrier island geology are usually based on cores to supplement bathymetric onshore offshore seismic and or ground penetrating radar gpr surveys the advantages and limitations of these methods with respect to barrier island investigations are briefly described in this review alternative near surface geophysical methods including electromagnetic induction emi sensors are increasingly being used for coastal research because they are non invasive provide continuous subsurface information across a variety of sub environments and are capable of characterizing large areas in a short time although these emi sensors have shown promise in coastal applications a number of issues primarily related to subsurface hydrology need to be addressed to fully assess the limitations of this technique this paper reviews the theory methodology and applications of emi in support of geologic framework studies with particular reference to barrier islands resolution of these issues will allow emi sensors to complement and offer significant advantages over traditional methods in support of an improved understanding of large scale barrier island evolution

impacts of vertically propagating tides on the mean state of the ionosphere thermosphere system the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model tie gcm is utilized to understand the role that upward propagating tides play in determining the zonal mean state of the ionosphere thermosphere system a sensitivity assessment of the tie gcm shows that tie gcm solutions greatly depend on the lower boundary conditions we also establish the veracity of our tie gcm solutions within and above the dynamo region to isolate the mean effects of tidal dissipation differences between tie gcm simulations with and without lower boundary tidal forcing as specified by the climatological tidal model of the thermosphere are investigated dissipation of the dw1 diurnal westward propagating tide with zonal wave number 1 diurnal eastward propagating tide with zonal wave number 3 and sw2 semidiurnal tide with zonal wave number 2 explains most of 10 30 m s 1 seasonal and latitudinal variability in zonal winds within the dynamo region with sw2 playing a greater role than ascribed in previous studies tidal dissipation at low latitudes causes a 9 decrease 30 increase in o o2 number densities near the f2 layer peak leading to at least a 9 decrease in peak electron density nmf2 throughout the year f2 layer peak height hmf2 differences of 4 to 2 km at low latitudes are explained by variations in the field aligned plasma motion driven by meridional wind differences induced by tidal dissipation compositional effects are mainly driven by dw1 and sw2 which differs from previous interpretations of tidal driven composition changes by dw1 tidal mixing exclusively we suggest that tides may produce a net transport of constituents in the thermosphere similar to the way that e g gravity waves can drive net transport of sodium in the mesosphere

tomographic imaging of the lowermost mantle with differential times of refracted and diffracted core phases pkp pdiff the mapping of variations in p wave speed in the deep mantle is restricted by the uneven sampling of p waves in particular beneath the southern hemisphere to enhance data coverage we augmented the 1 6 million summary rays of p pp and pwp that we used in previous studies with differential travel times of diffracted and refracted core phases for the core refracted differential travel time residuals pkpab pkpdf and pkpab pkpbc we used 1383 cross correlated digital waveforms as well as 27 000 routinely processed bulletin data we used the waveform data to define quality criteria for the selection and reduction of the bulletin pkp data for pkpdf pdiff we only considered 543 records derived from waveform cross correlation no pcp data were used in this study we used optical ray theory to calculate the ray paths associated with the p pp pwp and pkp data which are measured at 1 hz however to account for the large fresnel zones of the low frequency 50 mhz pkpdf pdiff data we estimated the three dimensional shape of the frechet sensitivity kernels from kernels calculated by normal mode summation the use of these kernels allows us to properly distribute the sensitivity for a given seismic phase over a large mantle volume while allowing the high frequency data to constrain small scale structure the differential times are relatively insensitive to source mislocation and to structure in the shallow mantle beneath source and receivers and they have previously been interpreted exclusively in terms of lateral structure directly above the core mantle boundary cmb however images thus obtained can be contaminated by effects of small scale structure elsewhere in the mantle here we do not make a priori assumptions about the mantle source of anomalous time differentials from test inversions we conclude that both upper and lower mantle structures that are poorly resolved by p data can be mapped into the core along pkp paths but that the effect of outer core structures if any on the mantle model is small compared to the inversion of the p pp and pwp alone the inclusion of the pkpab pkpdf and pkpab pkpbc and pkpdf pdiff data improves the resolution of structure beneath 2200 km depth in particular the joint inversion puts better constraints on the long wavelength variations in the very deep mantle and yields an increase in the amplitude of velocity perturbations near the cmb that is in agreement with but still smaller than inferences from shear wave studies resolution tests indicate that in some regions the enhanced definition of structure is significant but in most regions the improvements are subtle and structure remains poorly resolved in large regions of the mantle

airborne electromagnetic bathymetry and estimation of bedrock topography in broken bay australia abstracta helicopter transient electromagnetic tem survey was flown over shallow coastal waters in broken bay australia overlying several palaeovalleys and exposed reef sections the infilled palaeovalleys contain unconsolidated sediments with variable thicknesses exceeding 100 m previous marine seismic reflection and vibrocore studies provide an estimate of sediment thickness and surficial sediment conductivity respectively which combined with known bathymetry sonar soundings and measured seawater conductivity can be used to generate a crude 1d geoelectric ground truth model consisting of two layers seawater sediment overlying a relatively resistive basement the primary focus was to examine the accuracy of interpreted water depths obtained by 1d inversion of airborne tem data assuming a two layer over resistive basement model by comparing these depths with known water depths the secondary focus was to compare the interpreted sediment thickness i e the thickness of the second geoelectr

the variability of se2 tide extracted from timed saber observations based on the temperature observations of the timed saber in mlt region 70 110 km altitudes and at the low and mid latitudes 45 s 45 n from 2002 to 2012 the variability of the non migrating tide se2 with one day resolution is analyzed using the method from li et al 2015 it is found that the climatological features large scale variability of the se2 tide are similar with the results from the previous researches the se2 tide manifests mainly at the low mid latitudes around 30 the northern hemisphere tidal amplitudes below 110 km are larger than the southern hemisphere tide at the same time its peaks below 110 km mainly present between 100 and 110 km altitude the tidal amplitudes below 110 km occur a north south asymmetry about the equator in the annual variation in the southern hemisphere se2 occurs with an obvious annual variation with a maximum of tidal amplitudes in december while in the northern one the semi annual variations with maximum at the equinoxes herein owing to the high resolution tidal data we could research the short term day to day variations of se2 we found that the day to day variations manifests mainly at between 100 and 110 km altitudes it increases gradually with latitudes and it is stronger at the low mid latitudes it is relatively slightly stronger around solstices than equinoxes it does not present a remarkably inter annual variation the se2 day to day variations may be composed by the absolute amplitudes variance and the impact of the wave phases and the latter ones are more important

mapping the lower mantle determination of lateral heterogeneity in p velocity up to degree and order 6 the data from the international seismological centre bulletins for the years 1964 1979 are used to derive a three dimensional model of lateral variations of the p velocity in the lower mantle unlike previous studies in which such perturbations were represented by a blocklike parameterization we seek the solution in the form r k 0k l 0l m 0l k r kalm cos m kblm sin m plm cos some 500 000 travel time residuals for teleseismic distances from 5000 earthquakes are used in an iterative procedure to derive the coefficients a and b the maximum k and l used are 4 and 6 respectively in each iteration in addition to solving for the three dimensional structure we also relocate all the earthquakes perturb the average travel time curve and determine station corrections for over 1000 stations particular attention is given to the problem of weighting the individual observations in order to avoid as much as possible the bias due to the uneven distribution of sources and receivers the resulting model shows a high level of perturbations just below the 670 km discontinuity and just above the core mantle boundary where the maximum perturbations reach 1 1 5 of the average velocity even for this highly smoothed model at a depth of 2000 km the rms perturbations are some 3 to 4 times lower than at either of the two boundaries the model predicts well the large scale pattern of observed travel time residuals for various source regions except for the distinct effects of the subduction zones the most striking large scale three dimensional feature of the model is a ring of high velocities circumscribing the pacific basin within a depth range from 1000 km to the core mantle boundary if the proportionality between perturbations in the velocity and temperature is assumed the derived pattern of anomalies could be consistent with a two boundary layer model of convection in the lower mantle some caution however should be exercised in interpreting the results near the 670 km discontinuity where the resolving power of our data set is limited by the lack of adequate control of the upper mantle structure at the same time a significant global increase in the level of perturbations in the lowermost mantle is established beyond question the results of dziewonski et al 1977 on the correlation between the equivalent geoid and the observed geoid for the angular order numbers 2 and 3 is confirmed but there is no significant correlation for degrees from 4 to 6 these calculations are made for the rigid earth richards and hager this issue show that introduction of finite viscosity can change the sign of a geoid anomaly in addition recent studies of lateral variations in the shear velocity reveal the presence of large scale anomalies in the upper mantle thus while the inferences made here with respect to the origin of the gravest orders of the geopotential field are not conclusive they point the way in which results from seismology can be used to address some of the basic questions of geodynamics

lateral variations in mantle velocity structure and discontinuities determined from p pp s ss and ss sds travel time residuals on the basis of p pp s ss arrival times and ss s410s ss s660s differential times we construct models of mantle p and s velocity structure and boundary topography of the 410 km and 660 km discontinuities events from the catalog of the international seismological centre isc are relocated relative to the international association of seismology and physics of the earth s interior 1991 iasp91 velocity model using both p and s arrival times the arrival times are corrected for ellipticity and the pp and ss residuals are corrected for the topography at the bounce point the cap averaged pp p and ss s differential time residuals plotted at the pp and ss surface reflection points form broad coherent patterns the geographic distribution of the cap averaged residuals agrees quite well with pp p and ss s differential time residuals derived from long period global digital seismograph network gdsn data a robust lp inversion scheme is used to infer global mantle structure synthetic tests indicate that for regions well sampled by ss s410s and ss s660s differential times the velocity estimates are not seriously contaminated by the topography of the 410 and 660 km discontinuities however estimates of boundary deflections may be influenced by extensive p and s velocity variations of 3 or greater we find the 410 km discontinuity to be depressed by as much as 24 km beneath north america conversely the discontinuity is deflected upward underneath eurasia in some regions the topography of the 660 km discontinuity is quite distinct from that of the 410 km discontinuity but the two appear to be positively correlated a series of depressions are found at several intersections of the 660 km discontinuity with known subduction zones the elevated topography in the 410 km discontinuity beneath europe is underlain by a trough in the 660 km discontinuity a number of subduction zones are characterized by a thinning of the transition zone negative p and s velocity anomalies underlying back arc basins and tectonically active continental regions encircle the pacific where they are resolved the stable continental cratons are systematically positive velocity features that extend below 200 km with the inclusion of pp and ss travel time residuals we are better able to constrain midmantle structure most notably in the depth range 35 660 km beneath the northwest pacific we observe high p velocity where they are resolved mid ocean ridges are most clearly imaged as low velocity features in the s model the northern portion of the mid atlantic ridge is underlain by negative s velocity anomalies in the pacific the east pacific rise is an extensive low s velocity anomaly

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

resolution uncertainty and whole earth tomography 1 using the arrival times of 10 distinct phases from the international seismological center catalogue p s pp pcp ss scs pkpab pkpbc pkpdf sksac and two sets of differential times ss s410s and ss s660s we estimate the p and s velocity structure of the whole earth mantle outer core and inner core boundary topography of four interfaces within the earth hypocentral relocation parameters and station corrections the entire catalogue is relocated and reassociated using the radial velocity model ak135 both p and s phases are used in the relocation of over 41 000 events in depth isotropic velocity variations within the earth are parameterized by 22 layers lateral variations in shear and compressional velocity within the layers are represented by one of two grids in the mantle each layer is subdivided into 4560 equal volume cells of dimension 3 3 at the equator however in the outer and inner core the cell size is increased to 6 6 this change in grid spacing accounts for decreasing cell volumes with depth and variations in sampling between the mantle and core previous attempts using a fine grid throughout the earth resulted in poor resolution of core structure with the current grid the resolution of velocity heterogeneity in the mantle and outer core is comparable in the upper and midmantle the well resolved cells lie beneath eurasia and a narrow zone surrounding the mantle beneath the pacific basin in the lowest mantle the resolution decreases significantly an examination of the averaging kernels associated with six locations near the base of the mantle reveals the significant lateral and vertical averaging inherent in estimates of compressional velocity in well sampled regions of the outer core we are able to resolve compressional velocity variations in our 6 6 cells however velocity variations in the inner core are poorly constrained at the scale of our blocks in well sampled regions of the mantle and outer core model parameter standard deviations remain below 0 25 for much of the inner core the standard deviations are quite large exceeding 0 5 narrow high velocity anomalies are imaged in the upper mantle associated with subduction zones in a number of locations such as beneath the americas these features extend well into the lower mantle in the outer core heterogeneity is generally lower in magnitude of the order of 0 5 the most notable feature in the outer core is a systematic shift to slightly higher velocity in addition we find a roughly symmetric distribution of heterogeneity at the base of the outer core compressional velocities are generally higher in the equatorial regions and lower at the poles

longitudinal and seasonal variation of the equatorial flux tube integrated rayleigh taylor instability growth rate using the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model tiegcm the ionospheric rayleigh taylor instability growth rate is calculated the seasonal and longitudinal variations of the growth rate from the tiegcm appear to match that of the spread f observed by various satellite missions the growth rate is strongly dependent on the angle between the sunset terminator and the geomagnetic field line near the magnetic equator the tiegcm simulations with nonmigrating tides show the zonal wave number 4 structure in the rayleigh taylor instability due to the inclusion of the nonmigrating diurnal eastward zonal wave number 3 and semidiurnal eastward zonal wave number 2 tides

global earth structure inference and assessment summary a suite of compressional and shear phase arrival times p s pp pcp ss scs pkpab pkpbc pkpdf sksac and two sets of differential times ss s410s ss s660s are used to infer lateral variations in p and s velocity structure in the entire earth crust mantle and core volumetric heterogeneity is parametrized by 22 depth layers each of which is subdivided into a grid of cells in addition to volumetric hetero geneity we determine topography on the major internal velocity discontinuities station corrections event relocation parameters and inner core anisotropy a total of 96 300 unknowns the model parameters are estimated using an iterative lanczos algorithm to obtain a partial singular value decomposition a total of 5000 lanczos values and vectors are used to construct model parameter estimates as well as measures of model parameter resolution and covariance the lanczos resolution estimates provide lower bounds on conventional svd based measures throughout most of the mantle we find that regions beneath the continents particularly in the northern hemisphere are well resolved with the exception of africa velocity variations are moderately well resolved in that portion of the outer core lying beneath the continents velocity heterogeneity is poorly resolved in the inner core where cell dimensions are small and deviations in velocity heterogeneity trade off with variations in anisotropy variations in the uppermost mantle 2 3 per cent are correlated with surface tectonics while at greater depths high velocity variations coincide with regions of past and present subduction the high velocity anomalies extend into the lower mantle although with a reduced amplitude 0 5 1 0 per cent until the lowest mantle 2 5 per cent at the base of the outer core a large scale pattern of heterogeneity 0 8 per cent is observed slower at the poles in the inner core we infer a peak anisotropy of 2 3 per cent which varies laterally and with depth however the magnitude and distribution of the anisotropy trades off strongly with velocity heterogeneity

intra annual variability of the low latitude ionosphere due to nonmigrating tides 1 in situ plasma density measurements from the champ satellite between about 350 420 km altitude are used to delineate intra annual variations in the longitudinal structure of the f region ionosphere it is shown that the longitude structures during mid day local times are dominated by the space based longitudinal wavenumbers ks 2 4 and 3 in january july and december respectively these conform to the same dominating ks values characterizing solar thermal tide zonal winds in the dynamo region namely the westward propagating semidiurnal tide with planetary fixed zonal wavenumber s 4 sw4 and the eastward propagating diurnal tides with s 3 de3 and s 2 de2 respectively de3 is the dominating tide during the other months the results presented indicate that nonmigrating tides other than de3 may significantly impact the longitudinal structure of the low latitude ionosphere during certain months

strong evidence for the tidal control on the longitudinal structure of the ionospheric f region this paper presents for the first time the global latitude structure and seasonal variability of the ionospheric response to the forced from below de3 and de2 tides during the period of time january 2008 march 2009 the cosmic hmf2 and saber temperature data have been utilized in order to define the ionospheric de3 and de2 tidal response to the de3 and de2 temperature tides propagating from below the cosmic de3 and de2 hmf2 tidal oscillations are derived by the same method as the tides seen the saber temperatures it has been shown that the longitude wave 4 and wave 3 hmf2 structures observed respectively in september and may 2008 are forced mainly by de3 wave 4 and de2 wave 3 temperature tides coming from below the longitude wave 3 hmf2 structure observed in january 2008 however is forced by the combined action of the de2 temperature tide coming from below and the spw3 probably generated in situ

the influence of nonmigrating tides on the longitudinal variation of the equatorial electrojet 1 the climatological model of the equatorial electrojet eejm 1 derived from orsted champ and sac c satellite measurements provides the opportunity to investigate the longitudinal variation of the current strength in detail special emphasis is put in this study on the effect of nonmigrating tides we have found that the influence of the diurnal eastward propagating mode with wavenumber 3 de3 is particularly strong in polar orbiting satellite observations the de3 tidal signal appears as a four peaked longitudinal structure we have put special emphasis in our analysis to isolate the de3 contribution from other sources contributing to the wavenumber 4 structure in satellite data the amplitude of the de3 signature in the eej not only peaks during equinox seasons but is also strong around the june solstice when looking at the modulation of the eej intensity the de3 accounts for about 25 during the months of april through september it is thus the dominant cause for longitudinal variations during december solstice months the influence of de3 is negligible a secondary three peaked longitudinal pattern emerges during solstice seasons when the de3 influence is removed from the data available it is however not clear whether this pattern is related to any tidal drivers

attribution of ionospheric vertical plasma drift perturbations to large scale waves and the dependence on solar activity 1 in this study we quantify the contribution of individual large scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity we focus on migrating diurnal tide dw1 plus mean winds migrating semidiurnal tide sw2 quasi stationary planetary wave one qspw1 and nonmigrating semidiurnal westward wave one sw1 under northern winter conditions when qspw1 and sw1 are climatologically strong from thermosphere ionosphere mesosphere electrodynamics general circulation model simulations under solar minimum conditions it is found that the mean winds and dw1 produce a wave two pattern in equatorial vertical e bdrift that is upward in the morning and around dusk the modeled sw2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and dw1 sw1 can cause large vertical drifts around dawn while qspw1 does not have any direct impact on the vertical drift wind components of both sw2 and sw1 become large at middle to high latitudes in the e region and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift likely through modulating the e region wind dynamo the most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk reflecting the more dominant role of large f region pedersen conductivity and of the f region dynamo under high solar activity therefore the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions not only because variability is more identifiable in a quieter background but also because the e region wind dynamo is more significant these numerical experiments also demonstrate that the amplitudes phases and latitudinal and vertical structures of large scale waves are important in quantifying the ionospheric responses