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

estimating daytime vertical exb drift velocities in the equatorial f region using ground based magnetometer observations 1 the daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100 to 120 km altitude region within 2 latitude of the dip equator a unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the horizontal h component between a magnetometer placed directly on the magnetic equator and one displaced 6 to 9 degrees away the difference between these measured h values provides a direct measure of the daytime electrojet current and in turn the magnitude of the vertical exb drift velocity in the f region ionosphere this paper discusses a recent study that has established the quantitative relationship between the vertical exb drift velocity in the ionospheric f region and the daytime strength of the equatorial electrojet in the south american west coast longitude sector

radii shapes and topography of the satellites of uranus from limb coordinates abstract limb coordinates are used to find the radii shapes and local topography of the five large satellites of uranus the technique provides a direct measure of ellipsoidal shapes of satellites and fixes radii to subpixel accuracy umbriel titania and oberon are best fit by spheres miranda and ariel are ellipsoids whose equatorial bulges are consistent with published mean densities limb topography on miranda shows substantial deformation of both old cratered terrain and the younger coronae and complex faulting and uplift at the margins of the coronae the maximum deformation is about 10 km umbriel s limb shows a basin of undetermined origin about 500 km across and 6 km deep

unstable extension of enceladus lithosphere abstract regions near enceladus equator sarandib and diyar planitia contain extensive sets of parallel ridges and troughs that may be diagnostic of the region s formation conditions we present photoclinometry profiles across these ridges and troughs which indicate that they are periodic low slope features with dominant wavelengths of 3 to 4 km and amplitudes between 100 and 400 m the morphology of these terrains is consistent with formation via unstable extension of the lithosphere our numerical modeling demonstrates that unstable extension can generate large scale topography under enceladus like conditions comparison of our photoclinometry profiles with the dominant wavelengths produced by our numerical model permits estimation of the background heat flow at the time the sarandib diyar province formed we estimate heat flows of 110 to 220 mw m 2 suggesting that resurfacing of the planitiae was accompanied by strong localized heating the extension necessary to produce the ridges and troughs may have been caused by now inactive diapirs internal phase changes or other mechanisms our heat flux estimates imply elastic thickness at the time of resurfacing of 0 4 to 1 4 km which are sufficient to have allowed satellite reorientation if the province was underlain by a low density region it is therefore plausible that enceladus has experienced multiple heating events each leading to localized resurfacing and global reorientation

long duration penetration of the interplanetary electric field to the low latitude ionosphere during the main phase of magnetic storms 1 it is well known that the interplanetary electric field can penetrate to the low latitude ionosphere it is generally believed that the penetration of electric fields can last only for 30 min because of the shielding effect in the ring current in this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field imf in six cases the eastward electric field in the dayside equatorial ionosphere measured by the jicamarca incoherent scatter radar was enhanced for 2 3 hours after the imf turned southward and remained continuously southward in one case the eastward electric field in the dayside midlatitude ionosphere measured by the millstone hill incoherent scatter radar was continuously enhanced for 10 hours during southward imf since millstone hill is close to the equatorward boundary of the auroral zone during magnetic storms the penetration electric field there may be different from that at the equatorial ionosphere the most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay the electric field enhancements in the middle and low latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms the observations show that the interplanetary electric field can continuously penetrate to the low latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions

the long duration positive storm effects in the equatorial ionosphere over jicamarca the long duration positive storm lps in the equatorial regions is relatively poorly understood in this report we conducted a statistical analysis of the lps effects in the equatorial ionosphere over jicamarca 12 0 s 283 2 e in 1998 2010 there are 250 geomagnetic storms minimum dst 50 nt in 1998 2010 but the ionosonde observations at jicamarca are available only for 204 storms a total of 46 lpss are identified in terms of the criterion that the storm time relative deviation of peak density of f2 layer nmf2 exceeds 25 for more than 6 h a salient feature is that the occurrence of lpss tends to decay approximately exponentially on the following days after the main phase of geomagnetic storms the ratios of the number of equatorial lpss to that of geomagnetic storms have no obvious dependence on season and solar activity during the daytime lpss the disturbed zonal electric field is mostly westward as indicated from the geomagnetic field changes in the equatorial american region for the nighttime lpss the significant uplifting of f2 layer caused by an eastward electric field is the most important feature therefore the disturbed electric field should play an essential role in forming the equatorial lpss

a strong positive phase of ionospheric storms observed by the millstone hill incoherent scatter radar and global gps network 1 during geomagnetic storms the ionospheric f region electron density may be greatly increased or decreased which are termed positive storms or negative storms it is generally accepted that negative storm phases are caused by neutral composition changes in contrast different mechanisms have been proposed to explain the generation of positive storm phases in this paper we present observations of a strong positive storm at middle latitudes the millstone hill incoherent scatter radar detected significant increases of the midlatitude ionospheric f region electron density during a magnetic storm on 3 april 2004 the positive phase of the ionospheric storm started to occur in the morning sector 0912 lt at millstone hill and lasted for more than 10 hours compared with the quiet time ionosphere the daytime f peak altitude over millstone hill during the storm was 80 km higher the f region electron density was increased by a factor of 2 4 and the f region electron temperature was decreased by 1000 k or 40 the radar also measured an enhanced eastward electric field and a slightly more equatorward neutral wind global gps measurements show that total electron content tec was increased at middle latitudes and decreased at lower latitudes and the large tec enhancements occurred primarily in the atlantic sector we suggest that electric fields may play an important role in the generation of the observed positive storm phase the eastward electric field will cause increases in the midlatitude ionospheric electron density by moving the plasma particles upward and decreases in the equatorial ionospheric electron density by strengthening the fountain effect the daytime poleward wind was reduced or even reversed during the storm which may also contribute to the occurrence of the positive storm

investigation of permeable fracture zones by tube wave analysis summary in vertical seismic profiling tube waves are generally classified as noise they have however useful applications tube waves can be generated by compressional waves at fluid filled cracks crossing the wall of the borehole in this case the permeability of the fracture zone can be estimated from the amplitude ratio of the incident p wave and the generated tube wave in the present study an improved model for tube wave amplitude interpretation is presented while former models assumed isolated cracks now the consideration of fracture zones of a certain porosity permeability and width is allowed master curves are used to check the sensitivity of the amplitude ratio of tube and p waves with respect to the formal parameters of computation it is shown moreover that mainly those parts of a fracture contribute to the tube wave generation which are within a radius of about 1 m of the borehole the problem of localization and characterization of fracture zones by tube waves was investigated with several complementary field experiments in shallow boreholes in crystalline rocks as vertical seismic profiling vsp with three component borehole geophones and hydrophones televiewer measurements well tests and temperature measurements it turned out that fracture zones were met at all depths where tube waves were generated however not all of them were found to be hydraulically activated during well tests and temperature measurements this means that fractures detected by tube wave vsp are not necessarily of hydrological importance transmissivity values based on tube wave analysis are therefore an upper limit for the well under consideration on the other hand the transmissivity values derived from the well tests agreed quite well with those of the tube wave analysis if only the open fracture zones were considered a fact which seems to confirm our theoretical model

voyager 2 in the uranian system imaging science results voyager 2 images of the southern hemisphere of uranus indicate that submicrometersize haze particles and particles of a methane condensation cloud produce faint patterns in the atmosphere the alignment of the cloud bands is similar to that of bands on jupiter and saturn but the zonal winds are nearly opposite at mid latitudes 70 degrees to 27 degrees where winds were measured the atmosphere rotates faster than the magnetic field however the rotation rate of the atmosphere decreases toward the equator so that the two probably corotate at about 20 degrees voyager images confirm the extremely low albedo of the ring particles high phase angle images reveal on the order of 10 2 new ringlike features of very low optical depth and relatively high dust abundance interspersed within the main rings as well as a broad diffuse low optical depth ring just inside the main rings system nine of the newly discovered small satellites 40 to 165 kilometers in diameter orbit between the rings and miranda the tenth is within the ring system two of these small objects may gravitationally confine the e ring oberon and umbriel have heavily cratered surfaces resembling the ancient cratered highlands of earth s moon although umbriel is almost completely covered with uniform dark material which perhaps indicates some ongoing process titania and ariel show crater populations different from those on oberon and umbriel these were probably generated by collisions with debris confined to their orbits titania and ariel also show many extensional fault systems ariel shows strong evidence for the presence of extrusive material about halfof miranda s surface is relatively bland old cratered terrain the remainder comprises three large regions of younger terrain each rectangular to ovoid in plan that display complex sets of parallel and intersecting scarps and ridges as well as numerous outcrops of bright and dark materials perhaps suggesting some exotic composition

effects of disturbed electric fields in the low latitude and equatorial ionosphere during the 2015 st patrick s day storm the 2015 st patrick s day geomagnetic storm with sym h value of 233 nt is an extreme space weather event in the current 24th solar cycle in this work we investigated the main mechanisms of the profound ionospheric disturbances over equatorial and low latitudes in the asian australian sector and the american sector during this super storm event the results reveal that the disturbed electric fields which comprise penetration electric fields pefs and disturbance dynamo electric fields ddefs play a decisive role in the ionospheric storm effects in low latitude and equatorial regions pefs occur on march 17 in both the american sector and the asian australian sector the effects of ddefs are also remarkable in the two longitudinal sectors both the ddefs and pefs show the notable local time dependence which causes the sector differences in the characteristics of the disturbed electric fields this differences would further lead to the sector differences in the low latitude ionospheric response during this storm the negative storm effects caused by the long duration ddefs are intense over the asian australian sector while the repeated elevations of hmf2 and the eia intensifications caused by the multiple strong pefs are more distinctive over the american sector especially the storm time f3 layer features are caught on march 17 in the american equatorial region proving the effects of the multiple strong eastward pefs

storm time dependence of equatorial disturbance dynamo zonal electric fields we use jicamarca radar observations of f region vertical plasma drifts and auroral electrojet indices during 1968 1988 to study the characteristics and temporal evolution of equatorial disturbance dynamo zonal electric fields these electric fields result from the dynamo action of storm time winds and or thermospheric composition changes driven by enhanced energy deposition into the high latitude ionosphere during geomagnetically active conditions the equatorial vertical drift perturbations last for periods of up to 30 hours after large increases in the high latitude currents on the average this process can be described by two basic components with time delays of about 1 12 hours and 22 28 hours between the high latitude current enhancements and the equatorial velocity perturbations our data indicate strong coupling between dynamo processes with different timescales the short term disturbance dynamo drives upward equatorial drifts eastward electric fields at night with largest amplitudes near sunrise and small downward drifts during the day these perturbation drifts are in good agreement with results from the blanc richmond disturbance dynamo theory the dynamo process with time delays of about a day drives upward drift velocities at night with largest values near midnight and downward drifts in the sunrise noon sector in this case the amplitudes of the disturbance drifts maximize during geomagnetically quiet times preceded by strongly disturbed conditions we also present results of a new equatorial storm time dependent empirical model which illustrate the characteristics of the vertical disturbance dynamo drifts

hydrological aspects of geophysical borehole measurements in crystalline rocks of the black forest abstract one of six wells drilled into the crystalline rock of the black forest basement during the german continental deep drilling project ktb site survey has been used to detect hydraulically active fractures and to identify their character by a variety of logging tools such as caliper and televiewer logging vertical seismic profiling vsp and electrical and thermal measurements in addition to standard logging recordings in the 265 m moosengrund well drilled into the triberg granite body these methods were applied successfully to discriminate between fractures and breakouts and to identify open and closed fractures and water consuming or water expelling fractures respectively fracture strike dip and width were determined from televiewer data vsp measurements were used to determine the seismic velocities in the unfractured rock and the fracture zones estimates of permeability 10 55 darcy and transmissivity 0 1 1 0cm 2 s 1 of the fracture zones were obtained by the analysis of p waves and tube waves in the vsp records the summed values of the transmissivity yield an upper estimate of the overall transmissivity determined by a pumping test

high speed stream impacts on the equatorial ionization anomaly region during the deep solar minimum year 2008 1 to demonstrate high speed stream effects during the recent deep solar minimum year 2008 we have analyzed manually scaledfof2 and hmf2 at jicamarca and total electron content tec in the equatorial ionization anomaly eia region over the america longitudinal sector our results reveal that a prominent 9 day oscillation appears in the hmf2 and fof2 at the dip equator the 9 day oscillation amplitudes of fof2are not always positively correlated with tec in the equatorial ionosphere and they show nonlinear dependence on the intensity of geomagnetic disturbances with the outputs of fejer and scherliess s 1997 empirical model we found that this periodicity is also present in equatorial vertical drifts caused by disturbance dynamoelectric field ddef but absent in the drifts due to prompt penetration electric field ppef ddef effects on the equatorial periodic variations alone are not sufficient to explain the observed phenomena other mechanisms such as thermal expansion contraction and neutral composition changes are also the plausible causes of the periodic oscillation in the equatorial ionosphere further the complicated patterns appear in the 9 day band pass filtered tec perturbations in the eia region and they are quite different from the patterns of global coherent thermospheric oscillations triggered by high speed streams we also found that the latitudinal variations of band passed filtered tec present different behaviors involving tilt latitudinal configuration antiphased correlation between the crests and trough and south north asymmetry which vary as a function of season local time or even from event to event

sinker tectonics an approach to the surface of miranda images of the uranian moon miranda show three areas of complex terrain trapezoidal to ovoid in shape with no previously known counterpart these features called coronae are characterized by an inner core of intersecting ridges and troughs surrounded by a series of subparallel and concentric bands two of the proposed explanations for these tectonic features involve mantle convection driven by density anomalies the present study determines the surface stresses induced by such density anomalies and their expected surface expression miranda is modeled as having a rigid core surrounded by a mantle capable of viscous flow which is overlain by a thin elastic lithosphere the density anomaly is modeled as a point mass representing the sinker or riser the model is developed in a spherical coordinate system having axial symmetry about a 0 axis passing through the sinker the flow field set up by the sinking or rising mass is expressed in terms of a stream function using legendre sums streamlines are functions of the position of the mass anomaly and the radii of the core mantle and mantle lithosphere boundaries only magnitudes of the stream function depend upon the size of the mass anomaly its local gravitational field and the mantle lithosphere radius the stresses on the base of the lithosphere are then determined from the equations of motion the viscosity of the mantle material has no effect on the stresses produced at any given time but does control the velocity of the anomaly expressions for displacements and stresses in the elastic shell are developed as legendre sums and coupled to the viscous mantle solution with appropriate boundary conditions the stresses derived yield a pattern of expected tectonic expression this tectonic style varies with the radius of the body for a small body surface stresses are dominant in the area above the mass anomaly while farther away stresses at the base of the lithosphere control the tectonics directly over a sinker and extending outward 15 is a zone of both latitudinal and longitudinal surface compression which produces folding and thrust faults with no preferred orientation beyond 15 longitudinal stresses at the base of the lithosphere are extensional while latitudinal stresses are compressional producing a zone of folding and thrusts concentric about the sinker stresses induced by a riser are opposite in sign and predict extensional features with the same orientation as the compressional features predicted for a sinker stress magnitudes generally decrease with distance from the sinker and also decrease with both increasing sinker depth and lithosphere thickness the predictions of the sinker model are in good agreement with the tectonic styles of the banded and ridged terrains of miranda as determined from the topography as imaged by voyager 2 this agreement supports the idea that the coronae on miranda were produced by dense masses originally located near the surface that sank into miranda s interior for larger bodies the stresses at the surface and base are nearly equal longitudinal stresses are greater than latitudinal stresses resulting in compressional features with a preferred orientation radial to the sinker location the changeover in tectonic styles occurs at a planetary radius of approximately 1500 km

dynamic response of ionospheric plasma density to the geomagnetic storm of 22 23 june 2015 on 21 22 june 2015 three consecutive interplanetary shocks slammed into the earth s magnetosphere immediately after the third shock at 18 36 ut on 22 june marked by an exceptional sudden storm commencement with an amplitude of delta sym h similar to 106 nt a major geomagnetic storm commenced in the present study a multi instrument approach comprising observations data analysis and modeling is used to examine the global ionospheric response results show that enhanced storm time processes produced major total electron content tec variations at different latitudes longitudes and phases of the storm a closer inspection of the tec observations reveals strong longitudinal and hemispherical asymmetry in addition multiple equatorward and poleward propagating traveling ionospheric disturbances tids were detected in the tec data equatorward propagating tids are consistent with vertical neutral winds simulated from thermosphere ionosphere electrodynamics general circulation model however poleward tids were not reproduced in the model we find that a combination of driving processes including enhanced high latitude injection prompt penetration electric fields disturbance dynamo effect neutral winds and composition changes were acting at different stages of the storm

low latitude ionospheric thermospheric response to storm time electrodynamical coupling between high and low latitudes 1 using multi instrumental and multistation data we present low latitude ionospheric thermospheric behavior during the geomagnetic storm of 15 may 2005 the diurnal pattern of total electron content tec at a chain of equatorial to low latitude stations shows strong positive ionospheric storm on 15 may latitudinal variation of tec shows development of strong equatorial ionization anomaly eia on the same day evidence in terms of equatorial electrojet eej and magnetogram signatures is presented for the prompt penetration of interplanetary electric field ief as the cause of the positive ionospheric storm consequent to the storm time circulation resulting from the extra energy deposition via joule heating over high latitudes compositional changes occur in the global thermosphere tec enhancements on 16 may are attributed to enhancement of atomic oxygen at equatorial and low latitudes and the negative ionospheric storm on 17 may observed beyond certain low latitudes is explained in terms of enhancement of molecular species because of the storm time neutral composition changes strong esf plume structures on range time intensity rti map and l band scintillation and tec depletions in gps measurements are observed in the longitude sectors where the local time of sudden storm commencement ssc falls after the post sunset hours the ionospheric zonal electric fields are altered by the combined effects of eastward disturbance dynamo electric fields and direct prompt penetration of eastward electric fields associated with the northward turning of interplanetary magnetic field imf bz leading to subsequent development of esf after midnight

effects of prolonged southward interplanetary magnetic field on low latitude ionospheric electron density the present work describes the low latitude ionospheric variability during an unusually prolonged 33 h geomagnetically disturbed condition that prevailed during 15 16 july 2012 the low latitude electron density in summer hemisphere investigated using ground and satellite based observations responded to this by generating strong negative ionospheric storm on 16 july the maximum electron density on 16 july over indian low latitudes was reduced by more than 50 compared to that on a geomagnetically quiet day 14 july 2012 in contrast to the extreme reduction in total electron content tec in the northern hemisphere tec from a winter hemispheric station revealed substantial 23 total electron content unit 1 tecu 1016 el m 2 enhancements on the same day this contrasting hemispherical response in tec is suggested to be due to the combined effects of strong interhemispheric and solar driven day night winds further very weak equatorial electrojet eej strength on 16 july indicated that the westward electric field perturbations in the low latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes interestingly despite reduction in the integrated eej strength on 15 july the low latitude electron density showed substantial enhancement highlighting the significant effect of the positive ionospheric storm on the low latitude ionosphere the roles of electrodynamical neutral dynamical and compositional disturbances are discussed in view of these observations to understand low latitude ionospheric response when geomagnetic disturbance persists for longer duration

a new approach to the borehole temperature relaxation method summary the borehole temperature relaxation method is used to determine in situ thermal properties of rock by a thermal disturbance in an uncased borehole the conventional application of this method is based on the assumption that the heat flow through the borehole wall is constant in time and only a function of depth during the disturbance phase the new approach described in this paper offers a solution to the problem which does not refer directly to the thermal history during the disturbance phase it is only based on temperature measurements during the relaxation phase when the disturbance fades away by conduction the initial temperature disturbance t0 in the borehole the undisturbed temperature tf of the rock and the ratio p2c2 p1c1 of the thermal capacities of the rock and the borehole fluid are determined for given values of the corresponding thermal diffusivities x1 and x2 using a marquardt inversion scheme also formal errors of the determined parameters are derived a practical application to the data of a controlled experiment yields extremely low values for the in situ conductivity of the rock this unexpected result is probably a consequence of convective motions in the borehole during the experiment

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

equatorial disturbance dynamo electric fields f region vertical drift data from jicamarca peru show that equatorial east west electric fields are sometimes perturbed 16 24 hours after the onset of geomagnetic storms these disturbance dynamo electric fields which must be caused primarily by the action of neutral winds at low and middle latitudes decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime the long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed the data also show that after some storms there are no such delayed disturbances a fact which may be due to the longitudinal structure of the disturbances at high latitudes and or that only very strong storms can produce major thermospheric perturbations that extend to middle and low latitudes

formation of beta regio venus results from measuring strain beta regio is an area of rifting and volcanism on venus constituting a topographic rise a shield volcano theia mons lies near the center of the region and is surrounded by several radially oriented rifts we use magellan altimetry gravity and synthetic aperture radar data of the area to constrain some subsurface parameters first we derive hoop strain using altimetry data and a fault dip angle derived from the split crater somerville we determine the extension in the rifts surrounding beta regio we then derive the hoop strain accommodated by the rifts from the extension in these rifts except near theia mons the hoop strain follows the shape expected from a mantle upwelling the difference near the volcano we believe is due to volcanic infilling we then model three observable quantities the newly derived strain along with gravity and uplift using two separate modeling techniques one for the strain and uplift and another for the gravity the model results show that the data are consistent with the view that a relatively low density contrast region now exists below beta and has caused the uplift and rifting in the region

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

the transition to overshielding after sharp and gradual interplanetary magnetic field northward turning overshielding is referred to a shielding status during which the dawnward shielding electric field dominates over the duskward penetration electric field in the inner magnetosphere typically appearing when the interplanetary magnetic field imf suddenly turns northward after a prolonged southward orientation it is expected that the transition to overshielding after imf northward turning can be affected by the shape of northward turning sharp or gradual moreover the initial shielding status undershielding or goodshielding prior to the transition may also have influence on the transition here we analyze two groups of cases in which the transitions appear after sharp duration less than 5 min and gradual duration more than 30 min northward turning each group includes two cases in which the transition initiated from undershielding and goodshielding these cases show that 1 the beginning of the transition to overshielding coincides with sharp imf northward turning but appears in the midst of gradual imf northward turning 2 the transition from goodshielding to overshielding is always associated with convection electric field drop and or polar cap shrinkage regardless of the shape of imf northward turning and 3 the typical solar wind condition in which the imf suddenly turns northward after a prolonged southward orientation is neither a necessary condition nor a sufficient condition for overshielding furthermore we will discuss the effect of substorm processes on overshielding

day to day variability of the equatorial ionization anomaly and scintillations at dusk observed by guvi and modeling by sami3 1 the day to day variability in ionospheric irregularity generation giving rise to equatorial scintillation has remained an unresolved issue over many decades we take a fresh look at the problem utilizing the global imagery provided by the global ultraviolet imager guvi instrument on nasa s thermosphere ionosphere mesosphere energetics and dynamics satellite guvi has been acquiring images of 135 6 nm emission in the earth s ionosphere thermosphere system since 2001 these guvi disk images at dusk have been used to identify cases where the equatorial ionization anomaly eia crests lie near the magnetic equator over a relatively narrow longitude range so that the anomaly looks collapsed a 16 month period of guvi data collected during evening at solar maximum is used to study the morphology of these so called collapses since the eia collapse is shown to be linked to the suppression of equatorial plasma bubbles and scintillations in particular we look at the june solstice during which the atlantic and pacific show very different climatology and eia collapses are most frequent in the guvi data on the other hand eia collapses are a relatively rare occurrence during the equinox period when scintillations are most prevalent globally we obtained a few dramatic examples of day to day variability in eia behavior and scintillations over india the sami3 is also a model of the ionosphere sami3 model was used to investigate the conditions during the evening collapse of the anomaly in the indian longitude sector where measurements of total electron content tec and scintillations and estimates of the daytime vertical drifts and those at dusk were available results from sami3 show that the observed collapse of the anomaly at dusk can be simulated by a reversal of the upward vertical drift in midafternoon in agreement with the drift estimates from magnetometer observations such reversed vertical drifts at this time of the day are generally seen during counterelectrojet events introduction of neutral winds into sami3 better approximates the dusk behavior of tec at low latitude stations in india this study reveals that the longitudinally confined eia collapse may explain some of the differences in day to day variability of scintillations at different locations around the globe