prompt penetration electric fields ppefs and their ionospheric effects during the great magnetic storm of 30 31 october 2003 1 we explore the ionospheric effects of prompt penetration electric fields ppefs for a variety of interplanetary magnetic field directions we use the great magnetic storm of 30 31 october as an example of ppef effects for intense southward interplanetary magnetic fields imfs inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm concurrent with the above positive phase ionospheric storms occur in the dayside and negative phase ionospheric storms occur on the nightside the topics of this paper the dayside ionospheric storms due to ppefs are characterized by transport of near equatorial plasma to higher altitudes and latitudes forming a giant plasma fountain these features are part of what is called the dayside ionospheric superfountain dis for these southward imfs dusk and dawn plasma are predicted to be transported toward the dayside for northward imfs negative phase ionospheric storms are expected on the dayside if the ppefs indeed reach that region of space imf by components are expected to have weak or neglible ionospheric effects on the basis of ppef arguments intervals of imf by should not be related to geomagnetic storms they are not imf by intervals should however cause a shearing of the magnetotail a feature that has been previously reported in the literature

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

ionospheric annual anomaly new insights to the physical mechanisms the ionospheric annual anomaly or nonseasonal anomaly of the ionosphere is characterized by globally increased ionization in december solstice than in june solstice though this phenomenon was reported several decades ago the causal mechanisms have not been fully understood till today in this paper the f2 layer peak electron density nmf2 data from formosa satellite 3 constellation observing system for meteorology ionosphere and climate radio occultation observations during the low solar activity year 2009 were systematically analyzed to investigate the physical mechanisms responsible for annual anomaly and its local time latitudinal and longitudinal variability it is found that the annual anomaly is primarily dominant at southern hemisphere at all local times with significant enhancements at equatorial ionization anomaly crest latitudes during noon to afternoon hours and at high latitudes during nighttimes the annual anomaly in northern hemisphere occurs with relatively smaller magnitudes and confined only to morning to early afternoon hours 08 14 lt this study brings out the important roles of effective neutral winds due to the geomagnetic field configuration and the offset between geomagnetic equator and subsolar point for the enhanced plasma density in the southern hemisphere during december that majorly contributes to the ionospheric annual anomaly these results provide new insights to the responsible mechanisms behind the ionospheric annual anomaly and its local time latitudinal and longitudinal variation

multiple tectonic rotations and transform tectonism in an intraoceanic suture zone sw cyprus abstract new palaeomagnetic data from the late cretaceous neotethyan troodos ophiolite and related units in sw cyprus provide compelling evidence that transform tectonism is recorded outside the main outcrop of the fossil southern troodos transform fault zone sttfz high level intrusive and extrusive sequences were sampled along the sw margin of the troodos massif and in ophiolitic slivers preserved along arcuate fault lineaments further to the south and west these units show cross cutting relationships with corresponding differences in remanent magnetisation directions characteristic of syn magmatic rotation in an active transform setting net tectonic rotation analyses allow decomposition of the total rotation at these sites into early and late components early transform related rotations are consistently clockwise in agreement with all other studies of rotations associated with the sttfz further to the east late rotations and the net rotations derived at localities where cross cutting relationships were not present are regarded as composite in origin the composite rotation axes closely relate to the orientation of observed regional structures in these circumstances additional constraints are used to attempt geologically viable interpretations the overall distribution of transform related rotations steeply and shallowly plunging rotation axes and spreading axis related rotations sub horizontal rotation axes is comparable with that along the sttfz and adjacent parts of the troodos massif this is most readily explained by simple along strike extension of the primary spreading axis and transform fabrics into sw cyprus with minor late disruption by high angle dextral shear zones and neotectonic graben systems

spreading structure of the troodos ophiolite cyprus some paleomagnetic constraints it has been suggested that grabens on the northern flank of the troodos ophiolite formed by listric faulting in an oceanic environment and represent axial valleys fossilized by ridge jumping this paleomagnetic survey of the solea graben was carried out to constrain the structural interpretation an analysis was devised which restores both the dikes sampled to vertical and the primary remanent magnetizations to a previously derived structurally corrected remanent magnetization direction typically two solutions for the original dike orientation and the pole and angle of net rotation are obtained for each dike sampled these solutions can be separated if a locally consistent original dike strike is assumed reasons are discussed for the selection of the solution that gives an original northwesterly dike strike results are consistent with a graben rotations are up to 78 at the sites studied rotation vectors are subhorizontal and subparallel to the original dike strike suggestive of an axial process for the development of the structure however on the basis of field observations an alternative mode of origin is proposed invoking ephemeral extreme upper crustal extension by listric faulting on the west flank of an intermediate to fast spreading axis the grabens being formed by antithetic faulting

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

variabilities of the equatorial electrojet in brazil and peru 1 this report presents seasonal and longitudinal variabilities of the equatorial electrojet in the east brazil sao luis 2 3 s 315 8 e 0 5 s dip latitude and west jicamarca peru 11 95 s 283 13 e 0 6 n dip latitude coasts of the continent of south america ground based magnetic field perturbation measurements h for solar maximum 2001 2002 and solar minimum 2006 2007 conditions from the two equatorial stations sao luis and jicamarca have been used for the study the h signal which is a measure of the strength of the equatorial electrojet is spectrally analyzed using wavelet analysis the results of our analysis show that 1 the equatorial electrojet has maxima around equinoxes in jicamarca peru but it has a prominent maximum during southern hemisphere summer centered about december january in sao luis brazil the observed seasonal behavior of the equatorial electrojet in sao luis is highly likely due to the large magnetic declination angle about 20 west there 2 the equatorial electrojet is stronger in the west coast jicamarca compared to the east coast sao luis irrespective of solar activity condition 3 the magnitude of the equatorial electrojet is more variable with season and solar cycle over sao luis than over jicamarca

characteristics of penetration electric fields to the equatorial ionosphere during southward and northward imf turnings 1 the signatures of abrupt turnings of the vertical component of the interplanetary magnetic field imf bz can be seen at equatorial latitudes through the prompt transmission of high latitude electric fields to the lower latitudes called as prompt penetration electric field ppe the present work studies the signatures of ppe in daytime equatorial electrojet eej index derived in the indian sector during 2001 2005 the signatures are observed in polar pcn index and equatorial eej index ionosphere almost instantaneously 1 min the communication time of 12 6 min is observed between bow shock nose and the equatorial ionosphere and it is found to have inverse relationship with radial component of solar wind velocity during southward and northward bz turnings which might indicate magnetosphere crossing time scale by solar wind ionospheric reconfiguration time during southward turnings shows inverse relationship with solar wind flow in contrast to northward turnings with no relationship indicating differences in underlying physical mechanisms during both turnings we observe no local time dependence within 06 18 h in conductivity corrected eej signatures associated with bz turnings regression analysis between conductivity corrected eej and interplanetary electric field shows higher efficiency during northward turnings however further analysis investigating the effect of actual orientation of bz indicates that the magnitude of northward bz does not have influence on the ionospheric signatures it is noticed that the response signatures are mainly controlled by the magnitudes of southward bz thus the present study signifies the role of inner magnetospheric shielding electric field in addition to ceasing of convection during northward turnings

longitudinal variation of the lunar tide in the equatorial electrojet the atmospheric lunar tide is one known source of ionospheric variability the subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere there is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude we use magnetic field measurements from the champ satellite during july 2000 september 2010 and from the two swarm satellites during november 2013 february 2017 to determine for the first time the complete seasonal longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity significant longitudinal variability is found in the amplitude of the lunar tidal variation while the longitudinal variability in the phase is small the amplitude peaks in the peruvian sector 285 e during the northern hemisphere winter and equinoxes and in the brazilian sector 325 e during the northern hemisphere summer there are also local amplitude maxima at 55 e and 120 e the longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides a tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wavenumber 2 sw2 with secondary contributions by westward propagating modes with zonal wavenumber 3 sw3 and 4 sw4 eastward propagating waves are largely absent from the tidal spectrum further study will be required for the relative importance of ionopsheric conductivities and nonmigrating lunar tides

miocene remagnetisation of carbonate platform and antalya complex units within the isparta angle sw turkey abstract a palaeomagnetic study has been carried out within the mesozoic and tertiary units of the relatively autochthonous carbonate platforms and the allochthonous deep sea volcanics and sediments of the antalya complex exposed around the isparta angle sw turkey the antalya complex is interpreted as a mosaic of carbonate platforms basinal sediments volcanic and ophiolitic rocks which formed within a southerly strand of the neotethyan ocean adjacent to gondwana the results indicate a widespread remagnetisation event negative fold tests show that the remanence at most sites is of secondary origin e g within the cirali lavas the magnetisation is carried by magnetite of presumed authigenic origin the remagnetisation event is believed to have occurred in the early middle miocene burdigalian langhian it was possibly triggered by the migration of orogenic fluids ahead of the advancing lycian nappes during their emplacement onto the carbonate platforms subsequent to remagnetisation a large segment of the isparta angle underwent an anticlockwise rotation of 30 this rotation is attributed to the overall convergence and bending of the hellenic arc and the final stages of emplacement of the lycian nappes during the late miocene in agreement with previous studies previously southerly palaeolatitudes were inferred from late triassic extrusives of the godene zone calbali dag unit the post folding magnetisation identified here within the cirali lavas of the godene zone to the south implies that these low palaeolatitudes result from the inappropriate application of structural tilt corrections the available data cannot be used to substantiate an origin for the antalya units south of the equator in the early mesozoic instead a position close to the northern margin of gondwana is indicated

the impact of the january 15 2010 annular solar eclipse on the equatorial and low latitude ionospheric densities 1 the january 15 2010 solar annular eclipse crossed the magnetic equator in the middle of the day over india in a region instrumented with several magnetometers total electron content stations using gps data and an ionosonde located very near the center of the eclipse with the help of a one dimensional model appropriate for the region of interest we show that the ionosonde data was consistent with a lower f region plasma that was moving upwards with only modest velocities in the morning hours and moving resolutely downwards in the afternoon hours this motion agreed well with the local magnetometer data which revealed a weakened electrojet taking place in the morning hours while a full blown counter electrojet was present in the afternoon hours we show that the unusual solar eclipse induced electrodynamics resulted in a reduction in the total electron content depletion not just at the magnetic equator but also more markedly in the equatorial ionization anomaly eia zone a further 10 degrees to the north this latter point clearly shows that the eclipse led to a cut off in the supply of plasma provided through the equatorial fountain by altering a fundamental aspect of the equatorial electrodynamics

deflection of paleomagnetic directions due to magnetization of the underlying terrain in the summers of 1989 and 1991 we made 344 near ground level measurements of the ambient geomagnetic field above recent basalts on the island of hawaii using a three component fluxgate magnetometer we studied 12 surface features including a lava pond lava channels long tilted blocks smooth sloping surfaces two fissures and a deep u shaped road cut we observed substantial differences up to 20 between the observed and expected international geomagnetic reference field igrf magnetic field directions over these features except those composed of shelly pahoehoe and a flat horizontally thin lava pond we also observed inclinations that were systematically shallower than the igrf field by up to 5 we show that these shallower inclinations can be explained by the magnetization of the regionally sloping surface of the southern side of the island we found that all of the observed inclination deflections can be explained by simple two dimensional models which assume uniform induced and remanent magnetization parameters in the local terrain our observations imply that the inclination deflections cannot be corrected without a complete knowledge of the preexisting terrain and the remanence in the underlying flows upon which the lavas cooled since this information is rarely available it is difficult or impossible to discriminate between dispersion of paleomagnetic directions caused by the magnetic terrain effect and dispersion due to other factors such as paleosecular variation psv we therefore conclude that psv dispersion parameters cannot be accurately determined from paleomagnetic measurements on highly magnetic volcanic flows we also suggest that some of the geomagnetic excursions inferred from measurements on volcanic rocks may be at least in part due to the magnetic terrain effect it is unnecessary to invoke ad hoc mechanisms such as clastic block or crustal rotations distortion of the top crust or flow deformation to explain the large between site dispersions or inclination anomalies observed in many of the paleomagnetic data from volcanic rocks our observations also bring into question the general reliability of paleomagnetic pole positions inferred from volcanic rocks as a systematic inclination deflection due to local and regional slopes and irregular terrain such as those we observed would lead to a corresponding error in the inferred paleolatitude the magnetic terrain effects also offer alternative explanations for anomalous paleomagnetically inferred plate motions

equatorial anomaly in ionospheric electron content and its relation to dynamo currents using the ats 6 satellite radio beacon data collected over a chain of stations in the indian zone a study has been made of the equatorial anomaly in total electron content tec and its relation to the e region currents two parameters hd the difference in the magnetic field perturbation between the equator and a low latitude station and vd the backscatter radar measurement of the draft velocity of the electrojet irregularities are used to represent the equatorial current strength the results presented in the form of regression plots relating the strength of the anomaly and that of the current indicate that the anomaly dependence on the current strength is about the same for all the three seasons it is also noted that regardless of the season the anomaly crest moves toward a farther latitude from the equator with increasing current strength the total ionization inventory tec of the anomaly belt is found to increase linearly with the strength of the equatorial current and this result seems to bear some significance for the correlation observed between tecmax and hdmax at the equator

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

palaeomagnetism of palaeozoic ultrabasic rocks from the sudetes mts sw poland tectonic implications summary a complex palaeomagnetic rock magnetic and mineralogical study of ultrabasic rocks from the sowie gory block gsb and jordanow gogolow serpentinite massif jgsm revealed the presence of several components of natural remanent magnetization nrm the authors found three groups of palaeozoic as well as triassic and recent components of the geomagnetic field the palaeozoic components of nrm are carried mainly by magnetite of several generations formed during several serpentinization episodes permo carboniferous component a1 present overall the sudetes was isolated in one jgsm and two gsb exposures whereas the late devonian early carboniferous component a2 was found in two exposures from the gsb the corresponding remanent components were already revealed in palaeontologically dated sediments from other west sudetic units in the gsb it was probably acquired during its unroofing dated isotopically for ca 370 360 ma the newly determined group of palaeozoic directions a3 was found in three localities from jgsm and in two from gsb is interpreted as the oldest overprint in jgsm it was acquired probably shortly after the first oceanic serpentinization phase dated isotopically for ca 400 ma its acquisition in gsb corresponds to the time of emplacement of ultrabasic xenoliths dated isotopically at ca 390 ma so we suppose that the mean a3 calculated for five exposures corresponds to the 380 400 ma time span and that at that period both massifs formed one microplate mean inclination of a3 places this microplate at 380 400 ma at the palaeolatitude of 23 s whereas the west sudetes were situated during the early devonian at 16 s we suggest that during the early devonian the microplate comprising gsb and jgsm massifs was situated to the south from the west sudetes and accreted them during middle late devonian

ionospheric variability over indian low latitude linked with the 2009 sudden stratospheric warming in this paper we analyze radar observations of e b drift and plasma irregularities ionosonde observations of e and f layer parameters including spread f and magnetic field observations made from indian low latitudes linked with the 2009 sudden stratospheric warming ssw event e b drift variations presented here are the first of their kind from the indian sector as far as the effect of ssw is concerned difference of magnetic fields observed from the equator and low latitude h and e b drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior remarkable changing patterns in the critical frequency of f2 layer fof2 and f3 layer fof3 were observed after the occurrence of ssw large variations with quasi 16 day periodicity were observed in h fof2 and fof3 both semidiurnal and quasi 16 day wave modulation observed after the 2009 ssw event are consistent with those reported earlier we also noted quasi 6 day variations in h and fof2 soon after the ssw commencement not much reported before during the counterelectrojet events linked with the ssw event while equatorial es esq disappeared as expected there were no blanketing es esb a finding not reported and discussed earlier esb was also not formed at the off equatorial location indicating the absence of required vertical wind shear but e region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two weak f region irregularities were observed in the postmidnight hours and case studies suggest the possible role of ssw related background electric field in the manifestation of postmidnight f region irregularities

ionospheric electron content within the equatorial f 2 layer anomaly belt this paper describes some new results on the day to day behavior of the location of the equatorial anomaly in the columnar electron content the measurements were made from a unique network of stations covering dip latitudes from 0 n to 25 n during the period in 1975 1976 near sunspot minimum when the ats 6 satellite was visible from india the latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet rather than on the horizontal magnetic field measured only at the equatorial station during magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current the varying electrojet current that is the equatorial electric field is very effective in moving the ionization to the anomaly latitudes of 15 20 but the columnar electron content over the magnetic equator remains relatively constant

bransfield basin fine grained sediments late holocene sedimentary processes and antarctic oceanographic conditions the antarctic peninsula is sensitive to climatic change due to its northerly position and to the relatively reduced volume and character of its ice cover high resolution palaeoclimatic records from the ant arctic peninsula ice cores extend back only 500 years a climatic record of 2850 years in the bransfield basin is investigated through the analysis of sediment gravity cores from the floor of the central subbasin core gebra 1 and the slope of the eastern subbasin core gebra 2 sedimentological mineralogical and geo chemical properties have been systematically measured together with accelerator mass spectrometry ams radiocarbon dating the fine grained sediments result from two main processes hemipelagic settling from resuspensions and primary productivity and turbidity currents hemipelagic sediments were selected to investi gate the oceanographic and climatic conditions of the northern antarctic peninsula region during the last three millennia cold climatic periods are characterized by millimetric laminations and or black layers with higher organic carbon nitrogen and opal contents warm periods are recorded as massive to diffuse laminated facies with lower biogenic contents the results include the little ice age lia cold pulse as well as several 200 300 year long fluctuations within the lia and before this major climatic event of the holocene

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

equatorial ionosphere responses to two magnetic storms of moderate intensity from conjugate point observations in brazil 1 equatorial ionospheric responses during two magnetic storms of moderate intensity are investigated for the first time by conjugate point observations in brazil the study focuses on storm induced changes in the evening prereversal vertical drift thermospheric trans equatorial winds spread f plasma bubble irregularity development electron density plasma frequency heights the eia strength and zonal plasma drifts it is based on data obtained from five digisondes operated in brazil three of them being part of a conjugate point equatorial experiment copex involving a dip equatorial and two magnetic conjugate sites at 12 the other two were operated at the equatorial ionization anomaly eia trough and crest locations at nearby magnetic meridians the results bring out and clarify many outstanding aspects of the strong influence of storm time electric fields on the equatorial ionosphere at different phases of the two long lasting storm sequences during both storms prompt penetration electric fields dominated the ionospheric response features as compared to the disturbance wind dynamo effects that were not very conspicuous an under shielding over shielding electric field occurring in the evening hours causes enhancement suppression of the prereversal vertical drift and post sunset spread f plasma bubble generation the same electric fields cause post sunset eia enhancement and suppression respectively post sunset post midnight spread f can develop from under shielding over shielding electric fields while it can be disrupted by over shielding under shielding electric field trans equatorial winds are found to be ineffective to stabilize the post sunset f region against the destabilizing effect of strong prereversal vertical drift storm time westward plasma drifts are found to be driven by prompt penetration eastward electric fields through their effect of inducing vertical hall electric fields rather than by a disturbance westward thermospheric wind during these storms

response of the equatorial and low latitude ionosphere to an intense x class solar flare x7 2b as observed on 09 august 2011 1 in this paper we present response of equatorial and low latitude ionosphere to an intense solar flare of class x7 2b that peaked at 08 05 ut on 09 august 2011 in the solar cycle 24 global positioning system total electron content tec observations in the sunlit hemisphere show enhancement of 3 tec units while geomagnetic h component observations indicate sudden decrease and increase in their strength at equatorial and low latitude stations respectively at several stations in the sunlit hemisphere in addition equatorial electrojet strength over indian region reveals commencement of counter electrojet simultaneous canadian advanced digital ionosonde observations at tirunelveli an equatorial station in india show the disappearance of ionogram echoes during the flare event indicating absorption of radio signals in the d region strong equatorial blanketing type es layer was observed in the ionogram records at tirunelveli prior to the occurrence of the solar flare that continued for several hours though it became weak absent during the flare event ionogram records on the control day show regular f layer movement without any blanketing type es layer very low frequency vlf observations at allahabad an indian low latitude station show enhanced vlf amplitude signal during the same time revealing the sudden enhancement of d region ionization using the observations presented here an attempt has been made to study the impact of the solar flares on the electrodynamics of the equatorial and low latitude ionosphere

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

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

characteristics of intense space weather events as observed from a low latitude station during solar minimum 1 using a dual frequency high resolution software based gps receiver tec and phase have been monitored from calcutta india situated near the northern crest of the equatorial ionization anomaly for studying some space weather events during 2008 2010 data from a dual frequency ionospheric tec and scintillation monitor operational at this station under the international scinda program of the u s air force have also been used this paper presents two cases of intense space weather events occurring in the equatorial latitudes under magnetically quiet conditions during the abnormally prolonged minimum of solar cycle 24 high values of s4 with maximum 0 8 were noted on gps links located almost due south of calcutta 22 58 n 88 38 e geographic magnetic dip 32 n when the look angles of the satellites are more or less aligned with the axis of the anisotropic field aligned irregularities over the magnetic equator associated bite outs in tec of amplitude 40 units were recorded in the local post sunset hours well defined patches of phase scintillations and associated cycle slips were identified on these days higher values of ambient ionization were noted and the diurnal maximum of the electrojet strength was found to be delayed followed by a significant rise of the f region with a high upward drift velocity over the magnetic equator around sunset indicated by ionosonde measurements of in situ ion density using leo dmsp corroborate the f region height rise presence of irregularities in ionization density distributions around 450km was found from c nofs measurements

simultaneous storm time equatorward and poleward large scale tids on a global scale we report on the first simultaneous observations of poleward and equatorward traveling ionospheric disturbances tids during the same geomagnetic storm period on a global scale while poleward propagating tids originate from the geomagnetic equator region equatorward propagating tids are launched from the auroral regions on a global scale we use total electron content observations from the global navigation satellite systems to show that these tids existed over south american african and asian sectors the american and african sectors exhibited predominantly strong poleward tids while the asian sector recorded mostly equatorward tids which crossed the geomagnetic equator to either hemisphere on 9 march 2012 however both poleward and equatorward tids are simultaneously present in all three sectors using a combination of ground based magnetometer observations and available low latitude radar julia data we have established and confirmed that poleward tids of geomagnetic equator origin are due to ionospheric electrodynamics specifically changes in e b vertical drift after the storm onset

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

formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 november 2001 great storm this study investigates the 6 november 2001 great storm s impact on the topside ionosphere utilizing data from the onboard topex poseidon nasa altimeter defense meteorological satellite program special sensor ions electrons and scintillation instruments and ace interplanetary observatory a set of field aligned profiles demonstrate the storm evolution caused by the precursor and promptly penetrating interplanetary eastward electric e fields and strong equatorward winds reducing chemical loss during the long duration negative bz events at daytime evening the forward fountain experienced repeated strengthening as the net eastward e field suddenly increased the resultant symmetrical equatorial anomaly exhibited a continuous increase while the energy inputs at both auroral regions were similar in both hemispheres by progressing poleward a midlatitude shoulder exhibiting increased plasma densities a plasma density dropoff steep gradient and a plasma depletion appeared these features were maintained while the reverse fountain operated at the dropoff elevated temperatures indicated the plasmapause consequently the plasma depletion was the signature of plasmaspheric erosion in each hemisphere an isolated plasma flow supplying the minimum plasma was detected at the shoulder plasmaspheric compression due to the enhanced e fields could trigger this plasma flow exhibiting strong longitudinal variation at evening nighttime the shoulder increased 306 over the southeastern pacific where the nighttime weddell sea anomaly wsa appeared before the storm there the shoulder indicated the storm enhanced equatorward section of the quiet time wsa owing to the substantial equatorward plasmapause movement a larger poleward section of the quiet time wsa eroded away leaving a large depletion behind this study reports first these northern southern plasma flows and dramatic storm effects on a nighttime wsa

revised and synthetic apparent polar wander paths of the african eurasian north american and indian plates and true polar wander since 200 ma we have reviewed paleomagnetic data available for the eurasian african north american and indian plates over the last 200 ma selection criteria are those generally accepted with an emphasis on evidence for lack of remagnetization accurate dating and proper structural analysis this results in 23 35 51 and 2 poles for eurasia africa north america and india respectively we believe that this limited set of higher quality data is more likely to reveal key features of apparent polar wander apw paths than averaging of larger data sets involving less stringent selection criteria we propose and describe revised apw paths but more importantly we next use relative motion models to transfer all data in a common reference frame we find good agreement between transferred data when they are averaged separately for each plate in independent 20 ma windows this is a check on consistency of paleomagnetic data kinematic models and of the geocentric dipole hypothesis transferred data from all plates are averaged in 20 ma windows to generate synthetic apw paths for all plates studied these synthetic paths are in agreement with the original revised apw paths that use only data from a single plate moreover both geographic and time resolution are improved spatial confidence intervals are of the order of 5 the synthetic paths display interesting features such as a previously ill recognized apw loop for eurasia paleomagnetic and hotspot apw are next compared and a determination of true polar wander tpw is derived we find significant tpw amounting to over 20 in the last 200 ma tpw appears to be episodic with a standstill between 180 and 110 ma there is general agreement with a previous study of livermore et al 1984 the tpw standstill appears to correlate with a time of decreasing reversal frequency ending with the cretaceous long normal superchron other periods of fast tpw would seem to correspond to increasing reversal frequency however it is suggested that the major tpw hairpin at 50 ma might correspond to the collision of india with eurasia tentative correlations with core or mantle indicators can be understood as a result of couplings between the core mantle and lithosphere we believe primarily related to episodic evolution of the d layer

effect of progressive deformation on remanent magnetization of permian redbeds from the alpes maritimes france abstract the relationships among the anisotropy of magnetic susceptibility the finite strain and the characteristic remanent magnetization chrm have been investigated in deformed red sediments from the alpes maritimes in southeast france the magnetic properties of these rocks are due to hematite the finite strain is known from field studies of the shapes and orientations of green reduction spots and from optical microscopy and x ray texture goniometry studies of chlorite and illite the strain data permit a classification of the magnetic results according to four main stages of progressive deformation in the compaction stage magnetic anisotropy is flattened in the bedding due to compactional loading the chrm directions approximate to a fisherian distribution about a mean value close to the known permian direction for the region as deformation proceeds pencil structure first develops and the anisotropy is characterized by a prolate pattern with maximum axis parallel to the subhorizontal azimuth of the pencil structure and fold axes with increasing deformation the magnetic susceptibility ellipsoid becomes oblate and finally triaxial at these stages of high deformation the anisotropy patterns show that the hematite grain orientations are strongly influenced by the cleavage the remanence directions in deformed rocks do not correspond to a fisher distribution and eventually deviate strongly from permian directions these results show that paleomagnetic vectors are affected by the distortional strains which accomodate shape change in the rock simple tilt correction without compensation for the strain would yield incorrect paleopole positions an attempt has been made to compensate for the effects of deformation by regarding the remanent vector as a passive marker march 1932 equations for strain removal were applied to the remanence in two ways 1 a using strain data directly obtained in the field for each site and 2 b by converting the magnetic susceptibility anisotropy of each sample to a corresponding finite strain value correcting for the finite strain by both methods improves the within site grouping of paleomagnetic vectors in strongly deformed rocks strain removal assuming the march model results in overcorrection of the remanent magnetization data in low strain regions distortion may produce mechanical rotation of the hematite particles but recrystallization may alter the deformation mechanism in regions of high strain the limits of applicability of the passive marker treatment could not be tested adequately in the deformed red sediments of the alpes maritimes

longitudinal and seasonal structure of the ionospheric equatorial electric field 1 the daytime eastward equatorial electric field eef in the ionospheric e region plays an important role in equatorial ionospheric dynamics it is responsible for driving the equatorial electrojet eej current system equatorial vertical ion drifts and the equatorial ionization anomaly due to its importance there is much interest in accurately measuring and modeling the eef in this work we propose a method of estimating the eef using champ satellite derived latitudinal current profiles of the daytime eej along with h measurements from ground magnetometer stations magnetometer station pairs in both africa and south america were used for this study to produce time series of electrojet current profiles these current profiles were then inverted for estimates of the eef by solving the governing electrostatic equations we compare our results with the ion velocity meter ivm instrument on board the communication navigation outage forecasting system satellite we find high correlations of about 80 with the ivm data however we also find a constant offset of about 0 3 mv m between the two data sets in africa further investigation is needed to determine its cause we compare the eef structure in africa and south america and find differences which can be attributed to the effect of atmospheric nonmigrating tides this technique can be extended to any pair of ground magnetometer stations which can capture the day to day strength of the eej

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

quiet time variability of the gps tec and eej strength over indian region associated with major sudden stratospheric warming events during 2005 2006 1 this paper describes the quiet time variabilities of the ionospheric total electron content tec derived from the signals from global positioning satellite system gps recorded at several stations in india along with simultaneous observations of equatorial electrojet eej strength obtained from geomagnetic field variations during january march 2006 when sudden stratospheric warming ssw events occurred analysis of the observations presented here confirms that strong correlation exists among the variabilities in eej strength and gps tec observations investigations suggest that there exist large scale wave like structures with periodicity of quasi 16 day wave in the tec observations near the equatorial ionization anomaly eia crest quite similar to that of eej strength our observations also indicate the existence of morning enhancement and evening reduction of tec and eej strength and vice versa during ssw events similar to that reported elsewhere using these observations it is suggested that the quiet time variabilities seen in the gps tec over eia could be caused due to the nonlinear interaction of upward propagating planetary waves pws with atmospheric tides presence of similar periods in the eej strength and tec observations near the eia crest region supports the view that the large scale wave like structures seen in tec near the eia crest are associated with pws that are modifying the primary eastward electric field in the equatorial e region and hence the eej strength through non linear interactions with atmospheric tides

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

storm enhanced plasma density features investigated during the bastille day superstorm field aligned passes track true profiles such defense meteorological satellite program passes permitted investigating storm enhanced plasma density sed feature development during the bastille day superstorm in a comprehensive way we tracked equatorial ionization anomaly eia and sed features and their underlying forward fountain circulation and downward sed plume plasma flows respectively northward subauroral polarization stream e fields detaching plasma and producing sed plumes were also detected we assessed the effects of south atlantic magnetic anomaly and summer towinter interhemispheric plasma flows on the eia and found a southward dipping gradient in drift flow when no storm evening related fountain strengthening occurred we investigated the relative importance of different plasma sources in sed development an extremely large plasma enhancement seen over florida at 2200 ut on 15 july 2000 was a sed feature that was tracked by many gps total electron content tec maps as a 200 tec unit tecu enhancement we tracked its equally large conjugate pair over trelew argentine patagonia and unraveled their development their underlying sed plume supplied most of the plasma appearing between these two sed features a small and highly asymmetrical eia offered on each side a low baseline upon which the downward streaming sed plume plasma piled up contradicting a currently accepted explanation there was no enhanced fountain action detected to contribute 150 tecu to the 200 tecu later 2400 ut there was enhanced fountain action but sed plume contribution still dominated proven by observational evidence sed development is a complex process of sed plume plasma flows and equatorward wind effects that cannot be described by one single explanation

palaeomagnetic dating of the earliest continental himalayan foredeep sediments implications for himalayan evolution abstract between the time of the india eurasia collision 50 45 ma 1 and the climax of crustal shortening and thrust stacking in the himalaya when the main central thrust mct was active 21 ma 1 2 there is a ca 30 my gap about which little is known this paper aims to shed light on this period by dating the initiation of major erosion from the rising himalaya and the probable start of uplift a significant event in the orogen s history this was achieved by accurately dating for the first time the dagshai formation sediments of northern india which are interpreted as early himalayan foreland basin deposits that record initial large scale erosion of the orogen 3 oriented hand samples were collected from six sites and analysed using palaeomagnetic techniques both polarities are represented and the remanence passes a fold test fitting the measured palaeolatitude to that expected for the indian plate dates the dagshai formation at 35 5 ma 6 7 ma and this is taken as the time when the embryonic himalaya began to be strongly eroded and regionally uplifted

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming 1 the whole atmospheric model wam initialized with a data assimilation scheme is capable of simulating real sudden stratospheric warming ssw events the electrodynamics in the coupled thermosphere ionosphere and plasmasphere with electrodynamics model ctipe was driven by the wam thermospheric winds in january 2009 to study the response of ionospheric drifts during the ssw simulation results are compared with observations of the vertical drift at jicamarca and the equatorial electrojet eej in the asian sectors early morning upward drift and afternoon downward drift are reproduced in all longitudes in the simulations and are consistent with the available observations results also show that the occurrence time of the early morning upward drift and afternoon downward drift have significant phase differences between different longitudes simulations suggest that during the ssw the longitude dependence of the amplitude and phase of the equatorial vertical plasma drift is caused by the changing magnitudes of the migrating tides modulated by the geometry of the geomagnetic field some additional day to day variability and modulation of the phase structures at different longitudes in ionospheric vertical drifts during the ssw are possibly produced by the short term changes in the non migrating tides and by planetary waves

timing of uplift of the troodos massif cyprus constrained by sedimentary and magnetic polarity evidence abstract plio pleistocene sediments exposed around the ophiolitic troodos massif document spectacular uplift from below sea level to a maximum height of c 2000 m sedimentation reflects a dominant control of focused tectonic uplift modified by the effects of glacio eustatic sea level change and climatic change understanding the uplift and controls on deposition has been hindered by an inadequate age model here we present a preliminary investigation of the polarity of remanent magnetizations recorded within the upper part of the pliocene succession in the pissouri and mesaoria basins and from the pleistocene marine terrace deposits that border the troodos massif when integrated with available lithostatigraphic and biostratigraphic data the main results are as follows focused uplift of the troodos massif began during the late pliocene either between 2 14 and 1 95 ma or immediately prior to 1 77 ma shallow marine ophiolite derived clastic and bioclastic sediments accumulated in both the mesaoria and pissouri basins implying that the troodos massif was uplifted as a single tectonic entity non marine deltaic and fluvial facies prograded into both of the basins during the pleistocene 1 77 ma recent marine terraces in sw and south cyprus were cut and covered by littoral sediments from

impact of oscillating imf bz during 17 march 2013 storm on the distribution of plasma over indian low latitude and mid latitude ionospheric regions we show evidence of a positive ionospheric storm occurring simultaneously at the equatorial low and mid latitude ionospheric regions in the indian sector in response to an intense geomagnetic storm on 17 march 2013 the storm had its onset time coinciding with the local noon an on site digisonde at trivandrum dip equator recorded a sharp decrease in the height of f region peak in the afternoon which is a signature of westward electric field associated with a cej coupled with it was a simultaneous increase in tec in the entire indian region the magnitude of increase in tec decreased slowly northward of the dip equator and had almost no change near the anomaly crest further northward of the anomaly crest the tec started increasing again and at shimla a mid latitude station it had a value close to 2 times its monthly mean we surmise that the westward electric field resulting from the cej pushed the f layer at the dip equator down to the altitude regions where recombination and diffusion played minimal roles no loss of plasma due to diffusion while photo production of ions was still taking place led to an enhancement in the electron density near the equatorial low latitude region the joule heating of the thermosphere on the other hand gave rise to the tads which pushed the plasma up in altitude at the equatorial anomaly region it supplemented the loss of plasma at the anomaly crest region resulting in no change in the tec and a marked increase in the tec in the mid latitude ionosphere

low latitude ionospheric height variation as observed by meridional ionosonde chain formation of ionospheric ceiling over the magnetic equator a multipoint ionosonde observation campaign was conducted along the magnetic meridional plane in southeast asia to study ionosphere thermosphere coupling one station was near the magnetic equator and two of the other stations were at off equatorial latitudes 10 magnetic latitude the daytime ionospheric peak height hmf2 was analyzed for each season during the solar minimum years 2006 2007 and 2009 the peak height increased for 3 h after sunrise at the magnetic equator and off equatorial latitudes as expected from the daytime upward e b drift the apparent upward drift at the magnetic equator ceased before noon while the drift at the off equatorial latitudes continued upward and the layer height exceeded the equatorial height around noon the noontime limited layer peak height at the magnetic equator which was termed the ionospheric ceiling did not depend on the season while the maximum peak height at the off equatorial latitudes largely varied with each season numerical modeling using the sami2 code was conducted and the features of the ionospheric ceiling were reproduced quite well the dynamical parameters provided by the sami2 modeling runs showed that the ionospheric ceiling is formed by the field aligned plasma diffusion which is a part of the fountain effect

low latitude ionosphere response to super geomagnetic storm of 17 18 march 2015 results from a chain of ground based observations over indian sector in this paper we present unique results of equatorial and low latitude ionosphere response to one of the major geomagnetic storms of the current solar cycle that occurred during 17 18 march 2015 where dst reached its minimum of 228 nt here we utilized data from magnetometers chain of ionosondes located at tirunelveli 8 73 n 77 70 e geometry 0 32 n hyderabad 17 36 n 78 47 e geometry 8 76 n and allahabad 25 45 n 81 85 e geometry 16 5 n along with multistation gps receivers over indian sector the observations showed a remarkable increase of h f to as high as 560 km over tirunelveli magnetic equator with vertical drift of 70 m s at 13 30 ut due to direct penetration of storm time eastward electric fields which exactly coincided with the local time of pre reversal enhancement pre and caused intense equatorial spread f irregularities in ionosondes and scintillations in gps receivers at wide latitudes plasma irregularities are so intense that their signatures are seen in allahabad lucknow storm time thermospheric meridional winds as estimated using two ionosondes suggest the equatorward surge of gravity waves with period of 2 h suppression of anomaly crest on the subsequent day of the storm suggests the complex role of disturbance dynamo electric fields and disturbance wind effects our results also show an interesting feature of traveling ionospheric disturbances possibly associated with disturbance meridional wind surge during recovery phase in addition noteworthy observations are nighttime westward zonal drifts and pre related total electron content enhancements at anomaly crests during main phase and counter electrojet signatures during recovery phase