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

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

observations of global ionospheric responses to the 2009 stratospheric sudden warming event by formosat 3 cosmic 1 the global ionospheric response to a stratospheric sudden warming ssw is studied using three dimensional electron density maps derived from radio occultation observations of formosat 3 cosmic during the 2009 ssw periods results show that the ionospheric electron density at eia crests exhibit a morning early afternoon increase followed by an afternoon decrease and an evening increase indicative of a semidiurnal component during the ssw period which is consistent with recent studies the latitude altitude electron density slice maps show that the ssw related modifications of the equatorial plasma fountain interact with the existing summer to winter neutral winds and resulting in a north south asymmetry the global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning early afternoon inferred from the duration of the equatorial ionization anomaly eia enhancement following the enhancement prominent global eia reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen the ionospheric response to the 2009 ssw event is also compared with the usual seasonal variation during january february 2007 instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does the ssw period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 ssw event

equatorial vertical drift modulation by the lunar and solar semidiurnal tides during the 2013 sudden stratospheric warming during the 2013 stratospheric sudden warming ssw period the jicamarca unattended long term investigations of the ionosphere and atmosphere julia radar at jicarmarca peru observed low latitude vertical drift modulation with lows of 0 12 m s daytime maximum drifts between 6 13 and 22 25 january and enhanced drifts up to 43 m s between 15 snd 19 january the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model reproduces the prevailing vertical drift feature and is used to examine possible causes the simulations indicate that the modulation of the vertical drift is generated by the beating of the semidiurnal solar sw2 and lunar m2 tides during the ssw period the beating is observable since the magnitudes of lunar and solar semidiurnal tidal amplitudes are comparable the theoretical beating frequency between sw2 and m2 is 1 15 13 day which may be modified due to phase changes this study highlights the importance of the lunar tide during ssw periods and indicates that the equatorial vertical drift modulation should be observable at other longitudes as well

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

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

landslides induced by the wenchuan earthquake and the subsequent strong rainfall event a case study in the beichuan area of china abstract the wenchuan earthquake on may 12 2008 triggered massive landslides and a subsequent strong rainfall prompted the development of new landslides as well as the reactivation of some pre existing landslides the highest seismic intensity zone of the wenchuan earthquake in beichuan china was selected as a case study to analyze the influence of the earthquake and the subsequent heavy rains on landslide evolution we selected this study area 414 km 2 since it was close to the coseismic surface rupture and because it suffered strong ground motion based on the interpretation of high resolution aerial photographs and remote sensing imagery combined with field investigation 40 pre earthquake landslides and 2221 coseismic landslides were identified with total landslide areas of 2 68 km 2 and 30 81 km 2 respectively there were 134 large over 50 000 m 2 co seismic landslides that covered a surface area of 15 54 km 2 and represented approximately 50 4 of the total area of the co seismic landslides the coseismic landslides were mainly located on the hanging wall of the causative fault and on the steep valley sides of the jian river and its tributaries a strong rainfall event occurred four months after the wenchuan earthquake and induced 969 new landslides which covered a 6 90 km 2 area and enlarged 169 existing landslides 2 48 km 2 the landslides were identified in spot5 images ultimately we found that earthquake tremors and the subsequent rainstorm severely disturbed the surface strata resulting in a large number of landslides

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

resonance effect existence or not for landslides triggered by 2008 wenchuan earthquake a reply to the comment by drs xu chong and xu xiwei

spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china abstract the 2008 5 12 wenchuan earthquake seismic magnitude mw 7 9 according to the usgs triggered a great number of landslides a spatial database of landslides is built by interpreting the remote sensing rs data which covers 11 counties severely damaged by the earthquake with area of about 31 686 12 km2 the geological settings of the study area are detailed mapped including geologic structure and lithology the digital elevation model dem of the study area with resolution of 30 m 30 m is presented to address the topographic characteristics correlations between the occurrence of landslides with geological settings i e active faults the coseismic surface ruptures geological unit slope gradient slope elevation as well as slope aspect are analyzed using spatial modeling in gis with the aids of field investigations it can be concluded that the distance to the causative faults and slope gradient are much more important than other factors landslides are clustered distributed along the causative faults of f2 and f3 and landslides incidence are dramatically decreasing with the increasing of the distance to the causative faults the landslides incidence has an obvious increase near the active faults i e f1 landslide concentration lc landslides km2 has an obvious exponent increase with slope gradient however lc has no obvious relationship with geological unit and slope elevation the difference of lc value in each geological unit each slope elevation category maybe have been the result affected by slope gradient for each geological unit each slope elevation category and distance of each geological unit each slope elevation category to causative fault zone isoseismal map reflects the incidence of landslides in some degree and lc increases dramatically with intensity increasing almost all landslides occurred in the region above vi degree statistics result also indicates that in the near field of causative faults landslides tend to have the initial sliding direction similar to the movement of the causative faults and preliminary study shows that landslides incidence varies in different slopes with different structure and consequent slopes and obsequent slopes have a higher landslides incidence than other layered slopes

is the troodos ophiolite cyprus a complete transform fault bounded neotethyan ridge segment we report new paleomagnetic data from the sheeted dike complex of the troodos ophiolite cyprus that indicate that its northern limit is marked by a hitherto unrecognized oceanic transform fault system the style magnitude and scale of upper crustal fault block rotations in the northwestern troodos region mirror those observed adjacent to the well known southern troodos transform fault zone along the southern edge of the ophiolite a pattern of increasing clockwise rotation toward the north coupled with consistent original dike strikes and inclined net rotation axes across this region is compatible with distributed deformation adjacent to a dextrally slipping transform system with a principal displacement zone just to the north of the exposed ophiolite combined with existing constraints on the spreading fabric this implies segmentation of the troodos ridge system on length scales of 40 km and suggests that a coherent strip of neotethyan lithosphere representing a complete ridge segment bounded by transforms has been uplifted to form the currently exposed troodos ophiolite moreover the inferred length scale of the ridge segment is consistent with formation at a slow spreading rate during tethyan seafloor spreading and with a supra subduction zone environment as indicated by geochemical constraints

magnetic studies of magma supply and sea floor metamorphism troodos ophiolite dikes abstract dikes of the eastern troodos ophiolite of cyprus intruded at slow ocean spreading axes with dips ranging up to 15 from vertical and with bimodal strikes now ne sw and n s due to post 88 ma sinistral microplate rotation varied dike orientations may represent local stress fields during dike crack propagation but do not influence the spatial distributions or orientation distributions of dikes magnetic fabrics nor of their palaeomagnetic signals anisotropy of magnetic susceptibility ams integrates mineral orientation distributions from each of 1289 specimens sampled from dikes at 356 sites over 400 km2 in the eastern troodos ophiolite of cyprus in 90 of dikes ams fabrics define a foliation kmax kint parallel to dike walls and a lineation kmax that varies regionally and systematically magma flow alignment of accessory magnetite controls the ams with a subordinate contribution from the mafic silicate matrix that is reduced in anisotropy by sea floor metamorphism titanomagnetite has less influence on anisotropy occasionally intermediate and minimum susceptibility axes are switched so as to be incompatible with the kinematically reasonable flow plane but maximum susceptibility kmax still defines the magmatic flow axis such blended subfabrics of kinematically compatible mafic silicate and misaligned multidomain magnetite subfabrics are rare areas of steep magma flow kmax plunge 70 and of shallow magma flow alternate in a systematic and gradual spatial pattern foci of steep flow were spaced 4 km parallel to the spreading axes and 6 km perpendicular to the spreading axes ridge parallel separation of steep flow suggest the spacing of magma feeders to the dikes whereas ridge perpendicular spacing of 6 km at a spreading rate of 50 mm a implies the magma sources may have been active for 240 ka the magma feeders feeding dikes may have been 2 km in diameter stable paleomagnetic vectors in some cases verified by reversal tests are retained by magnetite and titanomagnetite in all specimens the stable components were isolated by three cycles of low temperature demagnetization ltd followed by 10 steps of incremental thermal demagnetization td 47 of primary a components 338 2 57 2 n 207 95 3 9 mean tub 397 8 c are overprinted by a b component 341 4 63 5 n 96 95 8 7 mean tub 182 11 c a and b components are ubiquitous and shared equally by the n s and ne sw striking dikes a component unblocking temperatures tub are zoned subparallel to the fossil spreading axis their spatial pattern is consistent with chemical remagnetization at some certain off axis distance determined by sea floor spreading a components indicate less microplate rotation and more northerly palaeolatitudes that are consistent with metamorphic remagnetization after some spreading from the ridge axis thus their magnetizations are younger than those of the overlying volcanic sequence for which chrms are commonly reported as 274 33 88 ma

paleomagnetic arguments for block rotations along the arakapas fault cyprus paleomagnetic data from the sheeted dike complex north of the arakapas fault reveal significant internal rotations the north south trending dikes have remanent magnetization directions close to the well known westerly paleomagnetic direction of the troodos massif whereas the east west trending dikes near the arakapas fault have northerly remanent magnetization directions the paleomagnetic data are in agreement with the apparent clockwise rotation of the dikes contrary to recent geological analyses which postulate that the pattern of dike trends is due to dike injection into a sigmoidal stress field along a sinistral transform fault the paleomagnetic results indicate clockwise rotations about vertical axes in response to a dextral shear in addition to the rotations around vertical axes small rotations around subhorizontal axes are inferred from the paleomagnetic data for tilted dikes thus these data reinforce the vertical intrusion hypothesis

impact of sudden stratospheric warming of 2009 on the equatorial and low latitude ionosphere of the indian longitudes a case study using the equatorial electrojet eej induced surface magnetic field and total electron content tec measurements we investigated the impact of the sudden stratospheric warming ssw of january 2009 on the equatorial electrodynamics and low latitude ionosphere over the indian longitudes results indicate that the intensity of eej and the tec over low latitudes extending up to 30 n exhibit significant perturbations during and after the ssw peak one of the interesting features is the deviation of eej and tec from the normal quiet time behaviour well before the onset of the ssw this is found to be coincided with the beginning of enhanced planetary wave pw activity over high latitudes the substantial amplification of the semidiurnal perturbation after the ssw peak is seen to be coinciding with the onset of new and full moon the response of tec to ssw is found to be latitude dependent as the near equatorial ne stations show the semidiurnal perturbation only after the ssw peak another notable feature is the presence of reduced ionization in the night sector over the ne and low latitude regions appearing as an ionization hole well after the ssw peak the investigation revealed the existence of a quasi 16 day wave in the tec over low latitudes similar to the one present in the eej strength these results have been discussed in the light of changes in the dynamical background because of enhanced pw activity during ssw which creates favourable conditions for the amplification of lunar tides and their subsequent interaction with the lower thermospheric tidal fields

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

lunar tidal winds between 80 and 110 km from uars hrdi wind measurements 1 recent observations and models show the considerable effects of upward propagating lunar atmospheric tides on many aspects of the ionosphere thermosphere system a key aspect of atmosphere ionosphere coupling is the wind field in the ionospheric e region circa 100 150 km where the dynamo generation of electric fields occurs yet global specifications of lunar tidal winds exist only in theoretical predictions although years of satellite observations on atmospheric winds exist with almost global coverage in the present paper we report on quasi global semidiurnal lunar tidal winds up to 115 km from data gathered by the high resolution doppler imager hrdi on board the upper atmosphere research satellite during the early years from 1991 to 1999 the observed lunar semidiurnal tidal winds are consistent with global scale wave model gswm simulations in both amplitude and phase with maximum amplitudes located between about 40 n 60 n around the solstices the peak amplitudes of the lunar tidal winds lie in the 10 15 ms 1range whereas those simulated by gswm lie between 15 and 25 ms 1 the smaller hrdi amplitudes are likely due in part to amplitude suppression in construction of the climatological mean resulting from year to year phase variability in the lunar tide it is also possible that wave dissipation is underestimated to some degree in the gswm

morphology of ionospheric f2 region variability associated with sudden stratospheric warmings the effect of sudden stratospheric warming ssw on the f2 region ionosphere has been extensively analyzed for the major event of year 2009 apart from a few reports on other major and minor events morphology of ionospheric responses during ssw can be better comprehended by analyzing such warming events under different solar geomagnetic and meteorological conditions we investigate the features of f2 region variability following the ssw events of 2010 2011 2012 2013 2014 2015 and 2016 using ionosonde data from the asian region covering a broad latitudinal range from 26 6 n to 45 1 n we find perceptible ionospheric variations in electron densities during these warming events which is accompanied by a large variation of 117 within enhancements as compared to a meagre variation of 11 within depressions during these events we also examine six months data at these latitudes and longitudes and find that the maximum and minimum variation in f2 layer critical frequency is observed during each ssw period the influence of quasi stationary 16 day planetary waves is seen during these ssw events further a recently proposed parameter ssw integrated strength by vieira et al 2017 to characterize ssw event with respect to ionosphere is also examined it is seen that it does not fit well for these seven ssw events at these latitudes and longitudes

evaluation of landslide mechanisms characterized by high speed mass ejection and long run out based on events following the wenchuan earthquake abstract in the 2008 wenchuan earthquake the mass ejection type of high speed and long run out landslide was an unusual hazard characterized by its dramatic phenomenon of a huge slope mass launching into the air and becoming airborne for a long distance quantitative and qualitative combined techniques were applied to reveal the formation mechanism of this type of landslide four prerequisites critical to form mass ejection are identified high position of the toe of the surface of rupture critical height and critical inclination of slope sufficient open space in the movement direction and adequate take off speed of ski jump like mass ejection these four area specific prerequisites provide a promising approach for screening and targeting the potential landslides subsequently a dynamic reliability analysis method that considers the feature of energy time distribution is proposed this site specific method provides a more credible evaluation by emphasizing the most significant period within the whole earthquake duration finally an aerodynamic inverse method combined with an energy conservation based method is applied in the quantitative evaluation to calculate take off speed of mass ejection this paper provides a viable solution for regional screening and site assessment for new potential targets of this type of landslide

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

preearthquake anomalous ionospheric signatures observed at low mid latitude indian station delhi during the year 2015 to early 2016 preliminary results we have analyzed five major earthquake events measuring greater than 6 on richter scale m 6 that occurred during the year 2015 to early 2016 affecting indian region ionosphere using f 2 layer critical parameters f o f 2 h m f 2 obtained using digisonde from a low mid latitude indian station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude 42 4 degrees n dip normal day to day variability occurring in ionosphere is segregated by calculating f 2 layer critical frequency and peak height variations delta f o f 2 h m f 2 from the normal quiet time behavior apart from computing interquartile range we find that the ionospheric f 2 region across delhi by and large shows some significant perturbations 3 4 days prior to these earthquake events resulting in a large peak electron density variation of similar to 200 these observed perturbations indicate towards a possibility of seismo ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events it was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone as given by dobrovolsky et al 1979 the thermosphere neutral composition o n 2 as observed by global ultraviolet imager across delhi during these earthquake events does not show any marked variation further the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event

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

seasonal interannual and short term variability of planetary waves in met office stratospheric assimilated fields met office stratospheric assimilated data have been used to study the variability of travelling planetary waves in the upper stratosphere during the last decade 1992 2001 to distinguish the various travelling and quasi standing waves a new space time filtering method has been developed the results of this analysis show that longer period planetary waves 10 t 20 days have significant amplitudes mainly during winter in both hemispheres westward propagating waves are dominant in the northern hemisphere but in the southern hemisphere eastward and westward propagating waves have comparable amplitudes and sometimes eastward propagating waves are dominant it is suggested that the main forcing of longer period travelling waves is an internal variability of the quasi stationary planetary waves in the tropo stratosphere and that the substantial activity of eastward propagating waves in the southern hemisphere is associated with seasonal changes of the general circulation of the middle atmosphere in the shorter period part of the wavelet spectra t 10 days westward propagating waves are dominant and the observed maxima in amplitude spectra can be identified with the first symmetric normal atmospheric modes the so called 5 and 4 day waves these waves present in the stratosphere during most of the year increase in amplitude during seasonal transitions analysis of the behaviour of wavelet amplitudes at different pressure levels shows that these normal mode waves propagate upward from the lower atmosphere and their amplitudes increase with altitude there exists also a substantial long period modulation of the 5 day wave amplitude with quasi period of about 30 days copyright 2004 royal meteorological society

midlatitude ionospheric responses to the 2013 ssw under high solar activity ionospheric responses to sudden stratospheric warming ssw are not well understood particularly in the midlatitudes and under high solar conditions during the 2013 ssw ionospheric disturbances were observed in eight locations on the meridional chain from 30 5 degrees n to 42 8 degrees n in northern china the midlatitude ionosphere responded strongly to the ssw despite being under high solar flux the f 2 layer maximum electric density increased by more than 80 and the peak height was elevated more than 60km well set and organized semidiurnal variations were recorded in early and middle january during the ssw in eight observation locations the expected f o f 2 decrease in the afternoon hours was not clearly discernible however nighttime enhancements occurred frequently the time period spectra of the average f o f 2 and zonal winds and meridional winds at altitudes of 86 95km presented quasi 16day planetary wave like oscillations during the warming event the coupling between the atmosphere and ionosphere may be strengthened by the quasi 16day waves the amplified diurnal semidiurnal and terdiurnal tides in f o f 2 were also recorded during the warming in good agreement with earlier observations importantly the variations in the semidiurnal tides included a 16day periodic component indicating that the modulated semidiurnal tides may transmit these 16day planetary wave like oscillations to the f region through wind dynamo although the pw tide interaction theory is not novel it is of significance in the midlatitude ionospheric response to ssw

september 2019 antarctic sudden stratospheric warming quasi 6 day wave burst and ionospheric effects an exceptionally strong stationary planetary wave with zonal wavenumber 1 led to a sudden stratospheric warming ssw in the southern hemisphere in september 2019 ionospheric data from esa s swarm

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

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

quasi 10 day wave and semidiurnal tide nonlinear interactions during the southern hemispheric ssw 2019 observed in the northern hemispheric mesosphere

tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism abstract the akamas ophiolite is shown to be a distal off axis extension of the main outcrop of cretaceous ophiolite in the troodos complex of cyprus mantle sequence harzburgites of both ophiolites share similarly oriented mantle flow fabrics and the same tertiary magnetizations acquired during exhumation however compared with the troodos mantle sequence rocks the akamas ferromagnetic mineralogy is more oxidized and remanences with lower blocking temperatures were acquired chemically paleopoles calculated from published vectors and our own new data define an apparent polar wander path apwp for the troodos microplate the apwp shows that between 88 and 50 ma the troodos microplate was equatorial and the vertical axis for its 60 anticlockwise rotation was located within the microplate subsequently the microplate drifted northward to 34 n with minor anticlockwise rotation at a reduced rate that requires microplate rotation about a vertical axis located to the west of cyprus in the last 50 ma the allochthonous triassic mamonia terrane docked with the cretaceous troodos terrane in sw cyprus within it disrupted tectonized ophiolite has been regarded as part of a triassic ocean floor or as sheared fragments of cretaceous troodos ophiolite incorporated into the mamonia terrane when it docked with the troodos terrane whatever their provenance their paleomagnetic signals postdate their penetrative deformation and metamorphism and their paleopoles may still be used to track their post strain motion our calculations of paleopoles from published vectors for the mamonia terrane smear along an extension of the apwp for the troodos microplate that is moreover concentric with the troodos microplate this suggests that the paleopole dispersion of the triassic mamonia rocks and their post magnetization disruption occurred during their accretion onto the anticlockwise spinning troodos microplate

aura microwave limb sounder observations of dynamics and transport during the record breaking 2009 arctic stratospheric major warming a major stratospheric sudden warming ssw in january 2009 was the strongest and most prolonged on record aura microwave limb sounder mls observations are used to provide an overview of dynamics and transport during the 2009 ssw and to compare with the intense long lasting ssw in january 2006 the arctic polar vortex split during the 2009 ssw whereas the 2006 ssw was a vortex displacement event winds reversed to easterly more rapidly and reverted to westerly more slowly in 2009 than in 2006 more mixing of trace gases out of the vortex during the decay of the vortex fragments and less before the fulfillment of major ssw criteria was seen in 2009 than in 2006 persistent well defined fragments of vortex and anticyclone air were more prevalent in 2009 the 2009 ssw had a more profound impact on the lower stratosphere than any previously observed ssw with no significant recovery of the vortex in that region the stratopause breakdown and subsequent reformation at very high altitude accompanied by enhanced descent into a rapidly strengthening upper stratospheric vortex were similar in 2009 and 2006 many differences between 2006 and 2009 appear to be related to the different character of the ssws in the two years

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

re computing palaeopoles for the effects of tectonic finite strain abstract the pre messinian limestone cover 58 8 ma to the troodos ophiolite 88 ma of southern cyprus is penetratively strained as shown by ubiquitous magnetic fabrics and in many sites stylolitic cleavage these define a gently n dipping foliation and an n plunging extension south vergent folding and thrusting is well known in very localized whereas the bulk of the strained limestone cover dips gently south disturbed by faulting the magnetic fabrics and stylolitic cleavage define the axes of finite strain in all sites studied and the calcite matrix was suitably ductile to permit the original palaeomagnetic directions to be de strained assuming continuum behaviour the optimum de straining 30 40 shortening in a flattening strain is compatible with the stylolitic cleavage development restores bedding to the near horizontal and restores the characteristic remanent magnetization vectors chrms to concentrated symmetrical fisherian distributions the strain corrected chrms yield more reasonable palaeopole locations for the lefkara and pakhna limestone and more uniform micro plate rotation rates corrected palaeopoles reveal a relatively uniform anticlockwise rotation of the troodos plate since the creation of the late cretaceous 88 ma ocean lithosphere it did not accelerate during the deposition of the limestone cover as required by palaeopoles calculated from data not corrected for finite strain but turned at 1 5 ma 1 since 58 ma

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

neotethyan intraoceanic microplate rotation and variations in spreading axis orientation palaeomagnetic evidence from the hatay ophiolite southern turkey abstract insights into tectonic processes operating in ancient ocean basins are provided by analyses of fragments of oceanic lithosphere preserved as ophiolites during collisional orogenesis here we present a palaeomagnetic analysis of the upper cretaceous hatay kizil dag ophiolite of turkey that provides evidence for intraoceanic microplate rotation and variations in ridge axis orientation in a neotethyan ocean basin magnetizations at 46 sites are shown to be pre deformational in origin and rotated from the relevant reference direction a net tectonic rotation approach to the analysis of the data provides information on permissible net rotation poles and angles and allows uncertainties in input vectors to be considered results demonstrate that all levels of the ophiolite have been rotated anticlockwise by angles in excess of 90 around steeply inclined axes the hatay ophiolite formed in the same supra subduction zone spreading system as the troodos ophiolite cyprus which is known to have rotated 90 anticlockwise in an intraoceanic setting in the late cretaceous to early eocene by considering our results in the context of the known timing of the troodos rotation we infer that 50 60 of rotation of the hatay ophiolite took place as part of an areally extensive troodos microplate this phase of rotation was triggered by initial impingement of the arabian continental margin with the neotethyan subduction trench consistent with models for modern day oceanic microplate rotation in complex convergent plate boundaries the hatay ophiolite then became detached from the actively rotating microplate and was emplaced onto the arabian margin in the maastrichtian undergoing a further 30 40 of anticlockwise rotation during thrusting back stripping of rotations allows correction of the hatay sheeted dykes to their initial orientations the restored dyke trend of 020 differs from that inferred previously for the troodos sheeted dyke complex demonstrating a primary variation in orientation of neotethyan spreading axes such variability is commonly observed in modern spreading systems in marginal basins these may act as analogues for the supra subduction zone spreading inferred for many ophiolites

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

ionosphere variability during the 2009 ssw influence of the lunar semidiurnal tide and mechanisms producing electron density variability to investigate ionosphere variability during the 2009 sudden stratosphere warming ssw we present simulation results that combine the whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the simulations reveal notable enhancements in both the migrating semidiurnal solar sw2 and lunar m2 tides during the ssw the sw2 and m2 amplitudes reach 50 m s 1 and 40 m s 1 respectively in zonal wind at e region altitudes the dramatic increase in the m2 at these altitudes influences the dynamo generation of electric fields and the importance of the m2 on the ionosphere variability during the 2009 ssw is demonstrated by comparing simulations with and without the m2 time gcm simulations that incorporate the m2 are found to be in good agreement with jicamarca incoherent scatter radar vertical plasma drifts and constellation observing system for meteorology ionosphere and climate cosmic observations of the maximum f region electron density the agreement with observations is worse if the m2 is not included in the simulation demonstrating that the lunar tide is an important contributor to the ionosphere variability during the 2009 ssw we additionally investigate sources of the f region electron density variability during the ssw the primary driver of the electron density variability is changes in electric fields changes in meridional neutral winds and thermosphere composition are found to also contribute to the electron density variability during the 2009 ssw the electron density variability for the 2009 ssw is therefore not solely due to variability in electric fields as previously thought

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

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

investigation on the variability of the geomagnetic daily current during sudden stratospheric warmings the magnetic field records of the magnetometer networks in the american east asian australian and european african sectors were employed in this present work we used them to investigate equatorial electrojet eej counter electrojet cej tidal variability in eej strength and ionospheric current during the 2005 2006 and 2008 2009 sudden stratospheric warming ssw events in addition to the well investigated tidal variability in eej strength over the american and east asian sectors we investigated that of the african sector for the first time interestingly the tidal components in eej strength during both ssw events clearly exhibit marked longitudinal differences with high moderate and low amplitudes in the american east asian and african sectors respectively an exception found around day 71 in the african sector after the 2008 2009 ssw event had higher solar diurnal tidal component as compared to that of the asian sector over the american sector solar and lunar semidiurnal tides were strongly associated with cej current during both ssw events whereas at the african and east asian sectors such variabilities are not evident a solar diurnal tidal component was strongly related to a reduction in the eej strength over the east asian sector in addition a prolonged period of cej occurrence that begins during the ssw precondition and ends when the ssw was evolving characterized the african sector during both ssw events there is a steady shift in phase at later hours when both ssw events are evolving

ionospheric response to the 2009 sudden stratospheric warming over the equatorial low and middle latitudes in the south american sector the present study investigates the ionospheric total electron content tec and f layer response in the southern hemisphere equatorial low and middle latitudes due to major sudden stratospheric warming ssw event which took place during january february 2009 in the northern hemisphere in this study using 17 ground based dual frequency gps stations and two ionosonde stations spanning latitudes from 2 8 n to 53 8 s longitudes from 36 7 w to 67 8 w over the south american sector it is observed that the ionosphere was significantly disturbed by the ssw event from the equator to the midlatitudes during day of year 26 and 27 at 14 00 ut the tec was two times larger than that observed during average quiet days the vertical tec at all 17 gps and two ionosonde stations shows significant deviations lasting for several days after the ssw temperature peak using one gps station located at rio grande 53 8 s 67 8 w midlatitude south america sector it is reported for the first time that the midlatitude in the southern hemisphere was disturbed by the ssw event in the northern hemisphere

reply to comment on tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism by g j borradaile and k lucas

coupling between mesosphere and ionosphere over beijing through semidiurnal tides during the 2009 sudden stratospheric warming 1 sudden stratospheric warming ssw in the winter of 2008 2009 is the strongest recorded ssw event the enhancement in semidiurnal variation of ionospheric tec total electron content with phase shift forward is shown during 22 to 27 january 2009 based on the tec observations in beijing 40 30 n 116 19 e geographic 39 73 n dip latitude we focus on finding the reason for the tec variation winds observed by an all sky meteor radar in the same observatory are used to study mesospheric variation the semidiurnal solar tide in the mesosphere starts to increase before the ssw and maintains oscillation with period 16 20 days during the ssw the semidiurnal lunar tides in tec and wind start to increase on 17 and 15 january respectively although the semidiurnal lunar tide in tec over beijing almost dies out on 1 february that over equatorial ionospheric anomaly crest does not vanish until 15 february when lunar tide in wind tends to be very weak the maximum of lunar tide in wind appears on 2 february at 96 km with amplitudes of 15 m s and 21 m s for zonal and meridional winds the phase comparison shows that lunar tides in tec and zonal wind reach their maxima at almost the same time which is 2 4 h lag behind the meridional wind the coupling between the mesosphere and ionosphere contributes to the semidiurnal variation of tec through both solar and semidiurnal lunar tides the enhancement in semidiurnal lunar tide is responsible for the tec peak shift forward during the ssw

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

landslide inventories the essential part of seismic landslide hazard analyses abstract a detailed and accurate landslide inventory is an essential part of seismic landslide hazard analysis an ideal inventory would cover the entire area affected by an earthquake and include all of the landslides that are possible to detect down to sizes of 1 5 m in length the landslides must also be located accurately and mapped as polygons depicting their true shapes such mapped landslide distributions can then be used to perform seismic landslide hazard analysis and other quantitative analyses detailed inventory maps of landslide triggered by earthquakes began in the early 1960s with the use of aerial photography in recent years advances in technology have resulted in the accessibility of satellite imagery with sufficiently high resolution to identify and map all but the smallest of landslides triggered by a seismic event with this ability to view any area of the globe we can acquire imagery for any earthquake that triggers significant numbers of landslides however a common problem of incomplete coverage of the full distributions of landslides has emerged along with the advent of high resolution satellite imagery

radar observations of long term variability of mesosphere and lower thermosphere winds over tirunelveli 8 7 n 77 8 e 1 the horizontal wind data acquired by mf radar at tirunelveli 8 7 n 77 8 e for the period january 1993 to july 2006 are used to study long term variability of equatorial mesosphere and lower thermosphere mlt winds the monthly mean zonal wind exhibits dominant semiannual variability with westward winds during equinox and eastward winds during solstice the first westward phase which occurs during spring equinox undergoes interannual variability with larger westward winds during the years 1993 1995 and 1997 this interannual variability has been interpreted as quasi biennial oscillation qbo in the mlt winds however this qbo is absent during the year 1999 as the next large westward wind phase occurs during the year 2000 thus the period of qbo is extended from nearly 2 to 3 years a during these years the period of stratospheric qbo winds is also extended to 3 a besides sao and qbo as the zonal winds undergo intraseasonal oscillations with periodicities resembling those of madden julian oscillation mjo in the troposphere the relation between the two is examined on the basis of the existing hypothesis the present study reveals long term variation in the amplitude of the annual oscillation noticed in monthly mean meridional winds a decreasing trend is observed in the annual mean northward winds during the years 1993 2006 in contrast to decreasing trend in the annual mean southward winds reported from midlatitudes these observations are discussed in the context of our current understanding of long term variability of mlt winds

interpreting anomalous magnetic fabrics in ophiolite dikes abstract anisotropy of magnetic susceptibility ams may reveal mineral orientation distributions defining magmatic flow axes in igneous dikes the mafic silicates are the best indication of magmatic flow but fe ti accessories may contribute more to the bulk susceptibility if the orientation distributions of the two subfabrics are incongruent anomalous fabrics will occur that do not reflect magma flow axes for ophiolite dikes ocean floor metamorphism changes the mineralogy producing new fe oxides by retrogression and exsolution from mafic silicates and by the oxidation of primary oxides incompatibly oriented ferro magnetic subfabrics may be isolated by anisotropy of anhysteretic remanence aarm anomalous ams fabrics in ophiolites elsewhere have been attributed to inverse fabric contributions from single domain magnetite in varying combinations however in ophiolite dikes from the troodos ophiolite of cyprus anomalous fabrics arise from ocean floor metamorphism extensively or completely replacing the original magnetite and titanomagnetite accessory phases with titanomagnetite fe 2 4 ti 0 6 o 4 tm60 and its oxidised versions titanomaghemite to varying degrees according to depth beneath the ocean floor distance from spreading axis and proximity to transform faults at best the oxide orientation distribution defined by aarm could only be indirectly related to magma flow if its nucleation orientation controlled by a host lattice however more commonly the topotactic lattice reorganization produces weaker arm fabric anisotropies although recrystallized oxidised tm60 dominates the bulk low field susceptibility its anisotropy is generally too feeble to compete with the flow fabric defined by the ams contribution from paramagnetic mafic silicates

causes of the longitudinal differences in the equatorial vertical e b drift during the 2013 ssw period as simulated by the time gcm during stratospheric sudden warming ssw periods large changes in the low latitude vertical drift have been observed at jicamarca as well as in other longitudinal sectors in general a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed during the january 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed at jicamarca the previously reported ssw behavior prevails however no shift of the daytime maximum drift was exhibited in the african sector using the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the possible causes for the longitudinal difference are examined the timing of the strong ssw effect in the vertical drift 15 20 january coincides with moderate geomagnetic activity the simulation indicates that approximately half of the daytime vertical drift increase in the american sector may be related to the moderate geophysical conditions kp 4 with the effect being negligible in the african sector the simulation suggests that the wind dynamo accounts for approximately 50 of the daytime vertical drift in the american sector and almost 100 in the african sector the simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 sw1 mainly contribute to the daytime wind dynamo and vertical drift numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence absence of a local time shift in the daytime maximum drift in the american african sector

planetary and gravity waves in the mesosphere and lower thermosphere region over tirunelveli 8 7 n 77 8 e during stratospheric warming events 1 an investigation of planetary wave pw activities in ukmo uk meteorological office winds during winter of the years 1998 99 and 2005 06 when major sudden stratospheric warming ssw events occurred shows that the amplitude of pw of zonal wave number 1 is considerably reduced in zonal winds when the warming event is onset and the reduced activity persists several days even after the end of the ssw event similar reduction of pw activity in zonal winds has been observed in the wavelet spectrum of mf radar zonal winds at altitudes 84 98 km over tirunelveli 8 7 n 77 8 e during this period of reduced pw activity enhancement in gravity wave activity is observed during 2005 06 and is not observed during 1998 99 and the mean meridional winds change to more equatorward during 2005 06 and remain poleward during 1998 99 in accordance with time gcm results our observations show that the wind reversal occurred in the stratosphere during major warming events allows more eastward gravity waves to propagate into the mesosphere and lower thermosphere mlt region which causes changes in the meridional circulation from poleward to equatorward

ams detection of inverse fabrics without aarm in ophiolite dikes inverse fabric contributions from single domain sd magnetite complicate interpretation of magmatic flow from anisotropy of magnetic susceptibility ams in the s troodos ophiolite dike swarm flow directions and magma chamber dimensions may only be inferred correctly if magnetic fabrics correspond to the orientation distribution od of minerals magnetite shape fabrics were isolated by anisotropy of anhysteretic remanence aarm but ams ambiguously merges magnetite and silicate fabrics however with the retrospective benefit of aarm in this area we recommend avoiding sd complications by excluding magnetite rich samples for which the bulk low field susceptibility 27 500 si magma flow was steeply upwards to the sw proximal to an axial magma chamber

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

longitudinal and interhemispheric ionospheric response to 2009 and 2013 ssw events in the african european and indian east asian sectors

palaeomagnetic insights into the evolution of neotethyan oceanic crust in the eastern mediterranean abstract a synopsis of palaeomagnetic data from three late cretaceous eastern mediter ranean tethyan ophiolites troodos hatay and baer bassit and their sedimentary coversequences is presented these data provide valuable insights into the role of regional andlocal scale tectonic rotations in the geodynamic evolution of neotethyan oceanic crust thegeologically earliest phases of tectonic rotation are documented in the troodos ophiolite where rotations around both subvertical and subhorizontal axes are readily related to thedevelopment of the spreading fabrics and structures during crustal genesis subsequent c 74 anticlockwise intra oceanic rotation of a troodos microplate has been quantified throughanalysis of the in situ sedimentary cover of the troodos ophiolite results indicate that bulkanticlockwise rotation began soon after the cessation of spreading and ended by the end ofthe eocene with c 50 60 of microplate rotation being over by the maastrichtian the timeat which ophiolite thrust sheets were emplaced onto the arabian continental margin to theeast of troodos recent results from the emplaced structurally dismembered baer bassitophiolite indicate extreme anticlockwise rotations of ophiolitic thrust sheets varying on akilometre scale new data from the post emplacement sedimentary cover confirm that onlya small component of these rotations is due to post emplacement tectonism baer bassitrepresents the leading edge of the emplaced ophiolitic sheet new data from the morecoherent section preserved in the hatay ophiolite to the north demonstrate significantanticlockwise rotation this is equivalent to the rotation of the most northerly part of thebaer bassit units to the south and is of the same sense and magnitude as the pre maastrichtian phase of microplate rotation documented in the troodos this suggests acommon intra oceanic origin for the majority of the troodos and hatay rotations and asignificant component of the more variable rotations observed in baer bassit overall therefore the data support a model involving 1 intra oceanic rotation of a coherent regionof crust within the southern neotethyan basin this rotated unit is more areally extensivethan has previously been inferred from consideration of data from the troodos ophiolitealone 2 emplacement of part of the rotated unit onto the arabian platform 3 subsequentlocalized post emplacement modification related to the development of the current plateconfiguration

late proterozoic reconstructions of north west scotland and central canada magnetic fabrics paleomagnetism and tectonics red beds dominate the stoer group and the unconformably overlying torridon group having accumulated between 1400 and 1000 ma in a rift of the hebridean foreland the sequences were weakly strained and shortened e w and each underwent successive diagenetic changes which altered their magnetic properties and caused their different characteristic post depositional magnetizations anisotropy of magnetic susceptibility ams reveals an n s vertical tectonic foliation superimposed on the bedding planar ams sub fabric the tectonic ams sub fabric was isolated by comparing normalized and non normalized mean tensors of multiple specimens the n s vertical ams tectonic foliation postdates warps of bedding thus the high susceptibility minerals including those carrying palaeomagnetic signals re oriented or recrystallized after deposition and diagenesis thus characteristic remanence vectors chrm were acquired long after deposition first in the stoer group then in the torridon chrms were isolated for 143 stoer specimens and 94 torridon specimens using two cycles of low temperature demagnetization followed by at least 12 steps of thermal demagnetization for the stoer group two structurally integral groups of sites yield mean magnetizations of 317 0 43 1 95 11 3 n 49 and 309 9 52 1 95 10 6 n 23 some stoer specimens bear a torridon age overprint 133 3 525 95 9 6 n 19 the younger torridon group yields 138 4 52 2 95 7 4 n 42 134 9 45 5 95 16 0 n 15 and 134 4 55 1 95 11 3 n 19 from three structurally integral clusters of sites these late chemical magnetizations postdate bedding warps faults and tectonic ams fabrics they do not warrant local rigid body tilt corrections however we restored the chrm directions for the regional post cambrian eastwards tilt which affected the entire foreland from the lewisian basement to the overlying proterozoic strata paleopoles calculated from the strata s restored vectors were rotated into laurentian coordinates for comparison with canadian proterozoic palaeopoles the stoer group was magnetized in a normal polarity geomagnetic field whereas the torridon group was magnetized in a reversed polarity epoch however both sequences include at least one polarity transition indicating long duration chemical magnetizations successfully averaging secular variation at a minimum red bed magnetization processes exceeded 0 1 ma and may have encompassed several million years during stoer group magnetization the hebridean craton was at paleolatitudes of 26 44 n when the torridon group magnetized it was at 23 27 s accepting published ages this defines a minimum southward latitudinal displacement rate of 27 40 km ma restored stoer group paleopoles lie in the present day north central pacific ocean 190e 25n corresponding to the laurentian apwp dated at between 1090 and 1109 ma torridon group paleopoles lie in the south central pacific 210e 25s near the poorly documented 900 ma southernmost part of the laurentian apwp

nonlinear interactions in the upper atmosphere the s 1 and s 3 nonmigrating semidiurnal tides 1 a semidiurnal oscillation with zonal wave number s 1 has been observed over the south pole and longitudinal variations of the semidiurnal tide at northern midlatitudes have been ascribed to the presence of nonmigrating tides a three dimensional nonlinear spectral model is used herein to study nonlinear wave wave interaction as a possible mechanism for the generation of nonmigrating tides in the mesosphere and lower thermosphere in particular the s 1 and s 3 nonmigrating semidiurnal tides are studied as a by product of the nonlinear interaction between the semidiurnal s 2 migrating tide and a stationary s 1 planetary wave in the lower and middle atmosphere this process is found to yield significant amplitudes 10 30 m s 1 of the nonmigrating semidiurnal components with s 1 and s 3 in the upper atmosphere comparisons with monthly nonmigrating tidal amplitudes and phases at 95 km derived from high resolution doppler imager and wind imaging interferometer wind measurements from uars show good agreement with the model simulations the effect of the dissipating nonmigrating tides on the zonal mean circulation is found to reinforce that of the migrating component contributing 10 20 m s 1 to the zonal wind field and 5 10 m s 1 to the mean meridional wind field several other wave components are generated through nonlinear interactions including 6 hour tides with zonal wave numbers s 0 1 4 and a semidiurnal oscillation with s 6 these wave components have amplitudes in the range 6 30 m s 1 in the 110 150 km height regime the combination of all nonmigrating tides together with the migrating component suggests significant longitudinal variations in the semidiurnal tide in the e region which may be important for studies of the quiet time generation of ionospheric electric fields by the dynamo mechanism

variations of mesospheric neutral winds and tides observed by a meteor radar chain over china during the 2013 sudden stratospheric warming the neutral winds in the mesospheric and lower thermospheric region obtained from a meteor radar chain within the latitudinal range of 18 53 n were decomposed to examine the latitudinal structures of the tides and mean winds during the sudden stratospheric warming ssw event in 2013 the zonal wind reversed from eastward to westward and the westward wind was larger at middle latitudes than that at low latitudes during the ssw meanwhile a sharp increase in the northward wind was noticeable at all stations the amplitudes of the diurnal and semidiurnal tides decreased from 5 to 13 january and increased subsequently at the same time the terdiurnal tides increased in amplitude especially at beijing wuhan and kunming in response to the ssw moreover the tidal phases showed a large shift that corresponded to a great increase in tidal wavelengths in the semidiurnal and terdiurnal components the wavelet analysis further revealed that the quasi 6 day wave oscillations dominated in the winds at kunming and sanya stations as well as the quasi 16 day wave dominated in the zonal wind and the quasi 11 day and 16 day waves were prevailing in the meridional winds at beijing and wuhan in the same vein the quasi 16 day and quasi 11 day waves were prominent in the zonal and meridional winds during 1 18 january at mohe therefore the tide planetary wave interactions played a significant role in modulating the behaviors of the mesospheric and lower thermospheric dynamics during the ssw event

comment on tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism by g j borradaile and k lucas

paleomagnetic quantification of upper plate deformation during miocene detachment faulting in the mohave mountains arizona 1 paleomagnetic data from miocene 20 ma volcanic rocks and dikes of west central arizona reveal the tilt history of proterozoic crystalline rocks in the hanging wall of the chemehuevi whipple mountains detachment fault we obtained magnetization data from dikes and flows in two structural blocks encompassing crossman peak and standard wash in the mohave mountains in the crossman block the dike swarm records two components of primary magnetization 1 cnh a normal polarity high unblocking temperature or high coercivity component inclination i 48 5 declination d 6 4 and 2 crhm a reversed polarity high temperature or high coercivity component i 33 6 d 197 5 argon age spectra imply that the dikes have not been reheated above 300 c since their emplacement and a baked contact test suggests that the magnetization is likely to be miocene in age crhm deviates from the expected direction of the miocene axial dipole field and is best explained as a result of progressive tilting about the strike of the overlying andesite flows these data suggest that the crossman block was tilted 60 to the southwest prior to intrusion of the vertical dike swarm and the block continued to tilt during a magnetic field reversal to normal polarity cnh miocene dikes in the crossman block are roughly coplanar so the younger dikes with normal polarity magnetization intruded along planes of weakness parallel to the earlier reversed polarity swarm an alternative explanation involves cnh magnetization being acquired later during hydrothermal alteration associated with the final stages of dike emplacement in the standard wash block the primary component of magnetization is a dual polarity high temperature or high coercivity component swhl i 7 2 d 0 7 to produce agreement between the expected miocene magnetic direction and the swh component requires 1 correcting for a 56 tilt about the strike of flow bedding and 2 removing a counterclockwise vertical axis rotation of 20 the two rotations restore the standard wash dikes to vertical make parallel the dike layering in the crossman and standard wash blocks and align the strikes of bedding in both blocks geologic mapping geochemical evidence and paleomagnetic data are consistent with the upper plate of the mohave mountains having tilted in response to formation of the underlying detachment fault

short term variation of the s 1 nonmigrating semidiurnal tide during the 2002 stratospheric sudden warming 1 in this study the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm is used to examine short term changes in the global structure of the migrating and s 1 nonmigrating semidiurnal tides in a model run approximating the 2002 southern hemisphere stratospheric sudden warming the time gcm is found to resolve an s 1 nonmigrating semidiurnal tide with latitudinal structure similar to that of prior studies and with global structure in the mlt region strongly correlated with southern hemisphere planetary wave 1 pw1 wave events prior to equinox comparison with a control run with no planetary wave activity eliassen palm flux and correlation analysis of the s 1 semidiurnal tide structure suggest that the wave propagates from the source region in the winter hemisphere stratosphere into both the summer and winter lower thermospheres the amplitudes of the migrating semidiurnal tide in the southern hemisphere are anticorrelated with the nonmigrating tide suggesting significant energy loss due to nonmigrating tidal generation a result not previously seen the amplitude of the s 1 nonmigrating semidiurnal tide from time gcm is also compared with data from the south pole meteor radar system while the observations show bursts of nonmigrating tidal activity correlated to pw1 activity of comparable amplitudes to the model results these events do not always appear at the same times as those in the model this suggests that while the processes generating the nonmigrating tide in time gcm are realistic the time gcm run itself displays differences in time evolution compared to the observations during this time

structures and microstructures related to steady state mantle flow in the neyriz ophiolite iran abstract structural analysis in the well exposed and well preserved neyriz ophiolite suggests that it is a relatively undisturbed piece of oceanic lithosphere detailed structural mapping of high t deformation mantle flow revealed the presence of three elliptical shaped diapirs trending nw se these diapirs are characterized by vertical mantle foliations associated with vertical plunging stretching lineations which progressively incline toward parallelism with the gently ne dipping moho the nw se direction of asthenospheric upwelling of diapirs is parallel with the orientations of the vertical sheeted dike complex this suggests that the neyriz ophiolite was created by two nw se palaeo ridge axes these palaeo ridges are classified as fast spreading ridges these ridges are segmented by a dextral palaeo transform fracture zone this is consistent with fast spreading ridges comparison between the neyriz and oman ophiolites reveals that they show similar characteristics most of the oman palaeo ridge systems are oriented nw se and nnw se they also display similar sheeted dike complex orientations and crustal thickness variations these two ophiolites originally were part of the neo tethyan oceanic lithosphere and afterwards were separated by the oman line during continental collision of the iranian micro continent and afro arabian continent

study of equinoctial asymmetry in the equatorial spread f esf irregularities over indian region using multi instrument observations in the descending phase of solar cycle 23 1 in this paper we present the results of a morphological study of equatorial spread f esf irregularities over indian region based mainly on observations of 1 amplitude scintillations on gps l band signal and rate of tec index roti obtained using a network of gps receivers and 2 amplitude scintillations on a vhf signal using spaced receivers at tirunelveli an equatorial station occurrence of both amplitude scintillations on the gps l1 signal and occurrence of significant roti recorded at several stations has been investigated the latitudinal extent of l band scintillations shows that their strength is weak over the dip equator but stronger over equatorial ionization anomaly eia region preferentially during vernal equinox we find an equinoctial asymmetry in both the occurrence of scintillations and roti wherein their occurrence is greater in the vernal equinox than in the autumn equinox attempts have been made to understand the asymmetry in latitudinal extent using maximum cross correlation ci of intensity fluctuations obtained from the vhf spaced receivers observations the observations suggest that occurrence of ci less than 0 5 is more in the vernal equinox than in the autumn equinox suggesting that the maximum height of the equatorial plasma bubbles epbs during vernal equinox may be higher than that during autumn equinox timed guvi retrieved peak electron density during the same period also indicates that background electron density is higher and more symmetric during vernal equinox than autumn equinox hence our results suggest that background electron density may be playing a vital role in creating the equinoctial asymmetry

paleomagnetic vectors and tilted dikes abstract where tectonic deformation reorients rocks without penetrative strain their paleomagnetic vectors may be restored to their original attitudes by untilting for strata paleomagnetic inclination is readily restored but the tilt axis must be precisely known if paleodeclination is required for dikes without the knowledge of the rotation s neither declination nor inclination of the paleomagnetic vector can be uniquely defined furthermore back rotating dike orientations to an upright attitude assumes primary verticality whereas primary dike dips are bimodal across the spreading axes e g troodos ophiolite cyprus in the cyprus ophiolite the dikes of the limassol forest transform zone are tilted due to uplift of the mantle sequence rocks and deflected against the arakapas fault their paleomagnetic vectors may be restored rotating about the two axes defined by the strike and the vertical or about a net axis that is possibly the actual tectonic rotation axis this net axis is determined from the tectonic regional dispersion of the dike orientations in this test case the results of the restorations differ slightly but underline the difficulty in selecting the best restoration procedure and the greater difficulty of restoring the paleomagnetic data from dikes vis a vis strata for dikes it is recommended that the paleomagnetic vectors are restored using average dike orientations to minimize the inaccuracies due to the large primary variation in dike orientation