intra annual variation of wave number 4 structure of vertical e b drifts in the equatorial ionosphere seen from rocsat 1 1 this paper studies the intra annual variation of the wave number 4 structure in the equatorial vertical e b drifts at high solar flux level based on of the rocsat 1 observations during the interval from 1999 to 2004 it is found that the daytime longitudinal structure is significant in northern summer and early autumn but weak in northern winter this is consistent with the intra annual variations of the tidal mode de3 at night the intra annual variation of the wave number 4 structure shows some differences from that in daytime which may relate to different dynamo mechanisms operating in different local time we also found that the wave number 4 structure mainly shifts eastward during daytime in most of months which is coincident with the eastward propagation of the de3 tide however it is largely disturbed near sunrise and sunset we attribute this disturbance as the jumping of the main dynamo region between e and f layers as well as the different dynamo mechanisms in different dynamo regions

longitudinal variability of low latitude total electron content tidal influences 1 recently nighttime ultraviolet uv observations obtained by image fuv and timed guvi instruments have revealed a longitudinal wave number four pattern in the nighttime airglow intensity and in the position of the equatorial anomalies during equinox and high solar flux conditions in the present study we have extended this work and determined the longitudinal variability of the low latitude total electron content tec climatology during different geophysical conditions with a special emphasis on the longitudinal wave number four structure in the low latitude ionosphere we have used more than 5 million low latitude topex tec observations covering the entire 13 years of topex tec data from august 1992 until october 2005 this data set was used to determine the local time seasonal solar cycle and geomagnetic activity dependence of the longitudinal variability of tec at equatorial and low latitudes and in particular to address the existence and evolution of the wave number four longitudinal pattern under these conditions our study shows that the wave number four pattern is created during the daytime hours at equinox and june solstice but is absent or washed out by other processes during december solstice during equinox the wave number four pattern is created around noon with well defined longitudinal enhancements in the low latitude tec these enhancements which are symmetric about the geomagnetic equator during this season last for many hours and can be clearly seen past midnight the longitudinal patterns are found to be nearly identical between the vernal march april and autumnal september october equinoxes and largely independent of the solar cycle conditions the wave number four pattern is also observed during geomagnetically active conditions indicating that the processes that create this pattern are also present during active times the variations between the well defined longitudinal maxima and minima are of the order of 20 during june solstice the wave number four pattern is also observed in the afternoon hours but in contrast to the equinox cases it exhibits a strong hemispheric asymmetry and is not observed during the night the low latitude tec exhibits clear longitudinal variations during december solstice with large daytime enhancements over the east asian and pacific regions and a third enhancement emerging in the afternoon over the atlantic ocean but a clear wave number four pattern is not observed during this season although the equatorial and low latitude tec values exhibit clear longitudinal patterns during all seasons a significant amount of scatter remains in the tec data that is not accounted for by changes in the solar cycle the season or the local time or by the longitudinal variability this remaining scatter is largest near the poleward edges of the anomalies and is of the order of 40

late variscan tectonic evolution by thinning of earlier thickened crust an 40ar39ar study of the montagne noire southern massif central france abstract 40ar 39ar age determinations on samples selected on deformational criteria form the basis of a proposal of a new detailed tectonometamorphic history of the montagne noire the southern part of the massif central france this range is classically divided into a cover and an axial gneissic and migmatitic core which was metamorphosed under high t medium p conditions the basement is structurally overlain by epimetamorphic paleozoic sediments in the north in the south equivalent rocks form a well known pile of recumbent nappes the variscan history of this area comprises early shortening and thickening of the continental crust the climax of this event took place around 320 ma ago as is shown by previous rb sr data and by 40ar 39ar measurements new developments in structural analyses have led to a better understanding of the late evolution of the area in terms of diapiric uplift of the core south southwestwards verging recumbent nappes have been emplaced and were weakly metamorphosed in their lower parts this movement was accompanied and followed by dextral extensional wrenching of the paleozoic cover along the northern and southern margins of the axial zone attendantly ductile shear zones were formed in order to decipher the complex history three structural levels have been dated with the 40ar 39ar method these levels are 1 the migmatitic and gneissic series in the axial core where micas yield ages of c 315 ma 2 mylonites from the northern and southern shear zones where biotites and muscovites yield ages of c 310 ma 3 muscovites and biotites from the epimetamorphic nappe structures yielding ages of c 297 ma the later ages may represent a younger thermal pulse these data are compared and discussed in the light of previous radiometric studies of the area and precise biostratigraphic constraints a detailed geodynamic evolution of the studied segment is proposed

three dimensional estimation of electron density over japan using the geonet gps network combined with sac c data and ionosonde measurements 1 the work presented here proposes a local tomographic approach to obtain a three dimensional description of the ionospheric electron density over japan to do this a combination of gps and ionosonde data is used in order to take advantage of the strong points of each data type the gps data is composed of ground and sac c low earth orbiter observations the ground observations correspond to measurements of 99 receivers out of about 1000 from the dense japanese gps network geonet sac c gps limb sounding observations are processed to obtain vertical profiles of electron density for this purpose an improved approach of abel inversion that considers vertical total electron content data has been used to overcome the assumption of spherical symmetry the resulting profiles have been averaged to build a set of background profiles which are rescaled with the ionospheric nmf2 values sounded by the japanese network of four ionosondes and used by the tomographic algorithm to provide with vertical description of electron density for the validation of this tomographic approach the hourly values of nmf2 given by the four japanese ionosondes and the vertical profiles of electron density measured by the mu radar in shigaraki during the sounding campaign of november 2002 have been used this validation with independent data shows relative discrepancies about 25 and moreover it shows that the use of the profiles obtained from sac c data offers an improvement on the dawn dusk and nighttime bottomside and topside estimations of the electron density with respect to the case of using the iri model

effects of complicated 3 d rupture geometries on earthquake ground motion and their implications a numerical study summary we present a numerical study of the effects of geometrically complicated 3 d ruptures on near source ground motions in most of the kinematic and dynamic rupture modelling studies or seismic moment tensor and slip inversions the strong assumption of a perfectly planar fault is made however it is known from geological field studies that real fault traces are not planar but characterized by relatively strong deflections bends and other irregularities in this paper we investigate the effects of such non planar earthquake ruptures on ground motion modelling in comparison to their equivalent planar ones for this purpose we apply the highly accurate discontinuous galerkin method that is capable of incorporating the geometry of complicated non planar rupture surfaces by a set of double couple point sources that do not have to coincide with the mesh vertices we generate a set of kinematic rupture models characterized by random spatial deflections with various correlation lengths and root mean square values these deflections then determine the associated spatial strike and dip variations we find that the deflected rupture models have the same seismic moment tensor as the perfectly planar one however with a reduced scalar moment which we correct for after a sound validation of our modelling approach we present the effects of the deflections on synthetic velocity seismograms computed in the vicinity of the rupture we observe that these geometrical irregularities do not just lead to high frequency effects but can strongly affect the synthetics in the whole frequency band finally we discuss our observations in detail and conclude that the correct incorporation of the geometrical properties such as local strike and dip variations of the rupture surface is an important issue we also discuss possible implications for some seismological fields such as strong motion simulations or seismic moment tensor and slip inversions where these results might have significant consequences

temporal modulation of the four peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave 1 observations of electron densities by the constellation observing system for meteorology ionosphere and climate in august to october 2008 have shown a prominent four peaked longitudinal structure in the height of the f2 layer hmf2 in the equatorial ionosphere the development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 it is believed that tidal winds can modify the e region electric fields and subsequently produce variations in the ionosphere through the dynamo effect this study reveals that the amplitude of the hmf2 four peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two month time period simultaneously wind measurements from the skiymet meteor radar at thumba 8 5 n 77 e india indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere mlt the 2 day planetary wave has both zonal and meridional wind components and it is the variability in the zonal component that most closely corresponds to f2 layer changes the zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave this study suggests that the identified 2 day variation of the hmf2 four peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the de3 tide and the 2 day planetary wave

isograds and mineral assemblages in the eastern axial zone montagne noire france implications for temperature gradients and p t history detailed petrography across a metapelitic sequence in the eastern axial zone of the montagne noire france is the basis for a sequence of isograds marking the first appearance of biotite cordierite staurolite andalusite and sillimanite the juxtaposition of low grade biotite free rocks against medium grade rocks at the gently dipping biotite cordierite isograd is attributed to tectonic telescoping of the metamorphic sequence study of mineral assemblages with respect to an afm reaction sequence indicates the staurolite isograd is related to changes in rock composition and complex assemblages in the sillimanite zone may be the result of unstable persistence of minerals formed when metamorphic grade was lower these assemblages are interpreted to contain a record of part of the p t history during which pressure decreased as temperature increased p t profiles show that temperature gradients of 200 300 c km suggested by previous workers are not required to explain the isograd pattern gradients of 37

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

estimates of the precision of gps radio occultations from the cosmic formosat 3 mission 1 the constellation observing system for meteorology ionosphere and climate cosmic formosa satellite 3 formosat 3 is a six satellite radio occultation mission that was launched in mid april 2006 the close proximity of the cosmic satellites provides a unique opportunity to estimate the precision of the radio occultation remote sensing technique from closely collocated occultations 10 km separation of tangent points the rms difference of refractivity between 10 and 20 km altitude is less than 0 2 which is approximately twice better than previous estimates obtained from champ and sac c collocated occultations apparently due to smaller separation of the occultation pairs and due to parallel occultation planes in the lower troposphere the maximal rms is 0 8 at 2 km altitude and decreases abruptly to 0 2 between 6 and 8 km altitude the rms difference of electron density in the ionosphere between 150 and 500 km altitude for collocated occultations is about 103 cm 3

origin of a large scale fold nappe in the montagne noire variscan belt france abstract detailed structural analysis of a large recumbent fold in low grade palaeozoic sediments of the montagne noire and the previously established tectonometamorphic history of its crystalline substratum indicate a two stage development history first relatively homogeneous crustal thickening produced folds with steep axial planes associated with a regional cleavage s1 subsequently these structures became rotated and amplified in a subhorizontal flow with pure shear and simple shear components related to low angle thrusting the development of an associated horizontal crenulation cleavage s2 with a component of vertical shortening of s1 plus evidence for a synchronous decompression of autochthonous units allows this flow regime to be placed in the context of a thrust wedge undergoing gravitational spreading above a continuously contracting footwall decoupling of an extending thrust wedge from a contracting footwall by a basal thrust with low shear resistance explains bulk shortening uplift and exhumation of mid to lower crustal autochthonous basement during thrusting and recumbent folding at higher levels structural relationships in the southern montagne noire demonstrate that traditional tectonic units recognized in this area the so called nappes are in fact unrelated to the recumbent folding as inferred previously these nappes postdate not only the recumbent folding but also a later phase of refolding d3 associated with the formation of a gneiss dome the traditional nappe division can be simplified to a hanging wall and footwall domain of a major decollement that formed during a second syn collisional collapse d4 associated with the formation of intermontane stephanian basins the late timing of the nappes and simplified tectonic structure of the southern montagne noire imply a thinner d2 recumbent fold structure with only one major anticline syncline pair and is in better agreement with the low metamorphic grade of the area

very low grade metamorphism of rheno hercynian allochthons variscides germany facts and tectonic consequences the horre belt in the se part of the rhenish massif has been regarded as autochthonous because of the apparent lack of metamorphic inversion we have performed a k white mica study using powder x ray diffraction derived kubler index ki and k white mica b cell dimension and the spectrally derived wavelength of the 2 200 nm absorption feature 2200wvl of supposedly allochthonous units and the underlying par autochthon ki reveals a slight but significant inversion of metamorphic grade which shows that the horre belt and the hessische schieferserie adjacent to the south were emplaced by thrusting after they had acquired peak metamorphism m 1 in deeper parts of the orogenic wedge only in the westernmost part of the study area the par autochthon and the allochthon show the same grade of anchizonal metamorphism this observation together with k white mica b cell dimensions 9 000 a and 2200wvl 2 204 nm suggests a second low pressure metamorphism m 2 subsequent to the emplacement of the allochthon this is supported by an anomaly of published conodont alteration index data our results expand the original width of the rheno hercynian passive margin to at least 580 more probably to 670 or even 750 km palinspastic restoration also reveals that the givetian to early carboniferous volcanic belt of the lahn dill area is not only younger than the emsian morb type lavas of the rheno hercynian ocean but was also separated from the latter by a largely non volcanic belt of at least c 220 km width apparently the givetian to early carboniferous volcanic episodes were unrelated to the rheno hercynian drift stage

wavenumber 4 patterns of the total electron content over the low latitude ionosphere 1 the global ionospheric maps gims produced by jpl are used to investigate the longitudinal structure of the low latitude ionosphere as a proxy of the ionization parameter at low latitudes the latitudinally integrated total electron content itec is first extracted from low latitude gims and then fourier filtered to obtain the wavenumber 4 components we then study in detail the diurnal seasonal and solar cycle variations of the wave patterns it is found that the wavenumber 4 patterns are intense and well developed in boreal summer and early boreal autumn but quite weak in boreal winter this seasonal variation is consistent with that of the zonal wind of the non migrating tide mode de3 we also found that the wavenumber 4 patterns shift eastward with a shifting speed that is smaller in daytime than at night this is attributed to the contribution of both the eastward propagation of de3 in e region and the zonal e b ion drifts in f region our results support the suggestion that the longitudinal wavenumber 4 structure of the low latitude ionosphere should be originated from the non migrating tide mode de3

viscous collision in channel explains double domes in metamorphic core complexes comment rey et al 2011 1 propose an appealing numerical model for the development of gneiss domes in an extending crust they suggest that extension in the upper brittle crust triggers oppositely verging ductile flows in the deep crust resulting in the rising of two domes of foliation separated by a

longitudinal variations of topside ionospheric and plasmaspheric tec the upward looking ionospheric total electron content tec from the metop a and tsx satellites during 2008 2015 has been used to systematically study the longitudinal variations of the topside ionosphere and plasmasphere the results of this study are summarized as follows 1 there are significant longitudinal variations in the topside ionosphere and plasmasphere at low latitudes the tec maximum during the june solstice over the western and central pacific ocean corresponds to a tec minimum at the same location during the december solstice but the opposite behavior occurs over south america and the atlantic ocean 2 during the solstices the relative longitudinal variations in the geomagnetic equatorial region do not have a strong dependence on local time and solar activity 3 the tec in the winter hemisphere decreases with increasing solar activity especially at higher altitudes and at night the topside tec depletion with solar activity depends on longitude 4 the solstice like longitudinal pattern lasts much longer than the equinox like patterns with the june solstice pattern lasting the longest furthermore the equinox like longitudinal patterns occur in march when expected whereas they extend from the autumnal equinox until the end of october 5 the longitudinal variations of upward looking tec are different from the corresponding longitudinal variations of electron densities around the f2 peak and orbital altitudes this indicates that the topside ionosphere structure is strongly influenced by the physical processes in the topside region rather than being a pure reflection of the ionospheric f2 peak structure

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

behavior of the f2 peak ionosphere over the south pacific at dusk during quiet summer conditions from cosmic data 1 the six satellite constellation observing system for meteorology ionosphere and climate cosmic mission makes routine ionospheric measurements over the entire globe using occultation techniques these observations have been used in this study to develop global scale climate maps of nmf2 and hmf2 during the southern northern summer winter enhanced electron densities that appear to be associated with the southern equatorial appleton anomaly are displaced far southward at dusk and within about an hour form the weddell sea anomaly coincidentally the height of the f2 peak increases on the northern boundary of this anomaly this height increase is also displaced southward as the enhanced electron densities are displaced southward suggesting that the electron density increases are associated with the f2 peak rising as well as being an interesting phenomenon in its own right this behavior may shed new light on the formation of the weddell sea anomaly no unambiguous explanation for this behavior can be determined from the data presently available but an examination of some possibilities suggests that an evening downward flux of plasma from the plasmasphere may be at least partly responsible for the phenomenon

the illite crystallinity technique a critical appraisal of its precision analysis of the precision of the illite crystallinity technique shows that machine errors are 0 8 it is necessary that contours should be at intervals of 0 1 2 which is equivalent to subdivision of the anchizone into upper and lower units where previous interpretations have relied upon an isocryst method of contouring at less than 0 1 2 the conclusions must be regarded as unsubstantiated centrifuge separation of clay fractions based on a stokes law application gives separations in which a significant but variable percentage of grains have long axes greater than the size calculated for the typical 2 m fraction utilized some 20 of grains lie in the 2 4 m range although the proportion is not believed to have a significant effect upon crystallinity values the formula is applicable for grain sizes down to 0 5 m illite crystallinity values on samples prepared by an ultrasonic disaggregation method show a small increase on those prepared by ball mill crushing the differences are minimal at the epi anchizone level but increase to some 10 at the anchizone diagenetic level the effect on grade determinations is again thought to be minimal and indicates that concern over unsuitability of the ultrasonic disaggregation method is unfounded

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

assimilative mapping of ionospheric electrodynamics in the thermosphere ionosphere general circulation model comparisons with global ionospheric and thermospheric observations during the gem sundial period of march 28 29 1992 satellite and ground based observations from march 28 to 29 1992 were combined in the assimilative mapping of ionospheric electrodynamics amie procedure to derive realistic global distributions of the auroral precipitation and ionospheric convection which were used as inputs to the national center for atmospheric research ncar thermosphere ionosphere general circulation model tigcm comparisons of neutral model winds were made with fabry perot measurements and meridional winds derived from ionosondes the peak equatorward winds occurred 1 2 hours later in the model gravity waves launched from high latitude joule heating sources reached the equator in about 2 hours and agreed with observed variations in the height of the maximum electron density hmf2 and in the meridional winds joule heating events produced minima in the o n2 ratio that moved equatorward and usually westward in longitudinal strips which lasted about a day changes in the o n2 ratio and in the peak electron density nmf2 were strongly correlated so the observed daytime nmf2 values for stations near 50 magnetic latitude were generally reproduced by amie tigcm on the second day of the simulation the amie tigcm underestimated the electron density after midnight by up to a factor of 2 in midlatitudes while the modeled f2 layer was about 35 km lower than the observations at midnight shifting the model winds 2 hours earlier at night could double the nmf2 at 0400 lt and increase hmf2 by 20 km nmf2 could also be increased at night by realistically increasing the tigcm nighttime downward fluxes of o at the upper boundary

a tectonic model for the emplacement of the main donegal granite nw ireland the main donegal granite is shown to lie in a major late stage ne sw trending transcurrent sinistral shear zone in the caledonides of nw ireland the zone which is bent both laterally and upwards around the pluton has displacements which diminish sw along its length from a maximum of approximately 20 km at the ne end of the pluton the granite has also been deformed by this sinistral shear but it has a strain component of its own the nature and development of which indicate that the pluton was accommodated rather than forcefully emplaced in the shear zone strain variations between granite and wall rock and an early plagioclase fabric associated with the petrographic banding of the granite suggest that intrusion and deformation were more or less synchronous at around 400 ma it is suggested that unconsolidated granite in the shear zone locally created high strain rates and instability which caused the zone to bend split lengthwise and progressively create an internal low pressure zone into which the main granite was emplaced the wide variety of emplacement styles of the other radiometrically synchronous plutons of the batholith can be attributed to the progressive development of the shear zone thorr and fanad in tension between the zone and a complimentary structure to the n ardara and toories in local compression at the shear zone termination rosses in tension on the outer arc of the bending zone and trawenagh bay as displaced main granite magma in a similar tensional setting during the final stages of deformation

a statistical study of ionospheric profile parameters derived from millstone hill incoherent scatter radar measurements diurnal seasonal and solar activity variations of the bottomside electron density profile parameters b0 and b1 representing the f2 layer thickness and shape are studied using a large incoherent scatter radar dataset for millstone hill covering the period 1976 2002 these results are compared with the latest iri model our statistical study is characterized by morning and afternoon falls in the diurnal variation of b0 for seasons other than summer and a similar to 15 change in b1 over a solar cycle features not fully well represented by the standard iri model the standard iri b1 however is very close to observations in terms of the diurnal variation

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

the montagne noire migmatitic dome emplacement french massif central new insights from petrofabric and ams studies in the southern french massif central the montagne noire axial zone is a ne sw elongated granite migmatite dome emplaced within visean south verging recumbent folds and intruded by syn to late migmatization granitoids the tectonic setting of this dome is still disputed thus several models have been proposed in order to better understand the emplacement mechanism of this dome petrofabric and anisotropy of magnetic susceptibility ams studies have been carried out in the granites and migmatites that form the dome core magmatic texture and to a lesser extent weak solid state texture are dominant as a paramagnetic mineral biotite is the main carrier of the magnetic susceptibility on the basis of 135 ams sites the magnetic fabrics appear as independent of the lithology but related to the dome architecture coupling our results with previous structural and geochronological studies allows us to propose a new emplacement model between 340 325 ma the palaeozoic series underwent a compressional deformation represented by nappes and recumbent folds involving the thermal event leading to partial melting until 325 310 ma the dome emplacement was assisted by diapiric processes an extensional event took place at 300 ma after the emplacement of the late to post migmatitic granitic plutons in the northeast side of the dome a brittle normal dextral faulting controlled the opening of the graissessac coal basin

physical mechanism and statistics of occurrence of an additional layer in the equatorial ionosphere a physical mechanism and the location and latitudinal extent of an additional layer called the f3 layer that exists in the equatorial ionosphere are presented a statistical analysis of the occurrence of the layer recorded at the equatorial station fortaleza 4 s 38 w dip 9 s in brazil is also presented the f3 layer forms during the morning noon period in that equatorial region where the combined effect of the upward e b drift and neutral wind provides a vertically upward plasma drift velocity at altitudes near and above the f2 peak this velocity causes the f2 peak to drift upward and form the f3 layer while the normal f2 layer develops at lower altitudes through the usual photochemical and dynamical effects of the equatorial region the peak electron density of the f3 layer can exceed that of the f2 layer the f3 layer is predicted to be distinct on the summer side of the geomagnetic equator during periods of low solar activity and to become less distinct as the solar activity increases ionograms recorded at fortaleza in 1995 show the existence of an f3 layer on 49 of the days with the occurrence being most frequent 75 and distinct in summer as expected during summer the layer occurs earlier and lasts longer compared to the other seasons on the average the layer occurs at around 0930 lt and lasts for about 3 hours the altitude of the layer is also high in summer with the mean peak virtual height being about 570 km however the critical frequency of the layer f0f3 exceeds that of the f2 layer f0f2 by the largest amounts in winter and equinox f0f3 exceeds f0f2 by a yearly average of about 1 3 mhz

topside ionospheric scale heights retrieved from constellation observing system for meteorology ionosphere and climate radio occultation measurements 1 the vertical scale height vsh in the topside ionosphere can be derived from electron density profiles in this study the electron density profiles retrieved from the cosmic formosat 3 a constellation observing system for meteorology ionosphere and climate mission c f3 for short ionospheric radio occultation iro observations have been collected to investigate the local time seasonal latitudinal and longitudinal variations of the vsh with the postprocessed c f3 iro electron density profiles during the interval from day of year doy 194 in 2006 to doy 60 in 2008 we conduct an analysis on the behaviors of vsh at an altitude of 400 km there are appreciable latitudinal variations in vsh a new finding is a significant peak around dip equator during daytime in four seasons away from the equatorial peak it is obvious that the vsh generally increases at higher latitudes the equatorial vsh undergoes a significant diurnal variation with a local noon maximum the peak shifts to sunrise time with increasing dip latitude and the values of daytime vsh become comparable with those at nighttime at low latitude in both hemispheres which is somewhat different from the feature revealed from arecibo incoherent scatter radar observations one of the crucial findings in our results is the most outstanding feature of vsh that is the presence of a substantial longitudinal structure in equatorial regions a wave like longitudinal feature is found in equatorial vsh during the daytime in four seasons while it becomes weaker or absent at other local time intervals and at higher latitudes this investigation also confirms that the behaviors of vsh are not strongly consistent with those of the neutral or plasma scale heights

double crests of peak height in the equatorial ionospheric f2 layer observed by cosmic for the first time we report daytime double crests of peak height hmf2 in the f2 layer based on the constellation observing system for meteorology ionosphere and climate cosmic observations during 2007 2014 evident double crests of hmf2 occurred at around 10 geomagnetic latitude with a trough over the magnetic equator at low solar activity and at march equinox this phenomenon is referred to as an equatorial height anomaly eha of the ionospheric f2 layer the double crests became less obvious at september equinox and disappeared at solstices at solstices only one crest was observed in the summer hemisphere which is probably associated with transequatorial neutral winds in addition the double eha crests generally take place during 10 00 14 00 local times our results indicate that the eha favors the conditions of strong vertical plasma drifts and weak transequatorial neutral winds during low solar activity the eha feature is reproduced by the thermosphere ionosphere electrodynamics global circulation model at march equinox and low solar activity

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

longitudinal structure of the equatorial ionosphere time evolution of the four peaked eia structure 1 longitudinal structure of the equatorial ionosphere during the 24 h local time period is observed by the formosat 3 cosmic f3 c satellite constellation by binning the f3 c radio occultation observations during september and october 2006 global ionospheric total electron content tec maps at a constant local time map local time tec map referred as lt map can be obtained to monitor the development and subsidence of the four peaked longitudinal structure of the equatorial ionosphere from lt maps the four peaked structure starts to develop at 0800 1000 lt and becomes most prominent at 1200 1600 lt the longitudinal structure starts to subside after 2200 2400 lt and becomes indiscernible after 0400 0600 lt in addition to tec ionospheric peak altitude also shows a four peaked longitudinal structure with variation very similar to tec during daytime the four peaked structure of the ionospheric peak altitude is indiscernible at night with global local time maps of ionospheric tec and peak altitude we compare temporal variations of the longitudinal structure with variations of e b drift from the empirical model our results indicate that the observations are consistent with the hypothesis that the four peaked longitudinal structure is caused by the equatorial plasma fountain modulated by the e3 nonmigrating tide additionally the four maximum regions show a tendency of moving eastward with propagation velocity of several 10 s m s

thrust related diapiric and extensional doming in a frontal orogenic wedge example of the montagne noire southern french hercynian belt abstract the montagne noire which is situated at the toe of the orogenic wedge of the french massif central south european variscides appears to be a well suited area for studying the origin and evolution of middle to upper crustal domes adjacent to foreland basins the data reported in the present paper show that the montagne noire dome is a particular type of basement involved frontal culmination in an orogenic wedge and foreland basin system this frontal culmination is characterized by a syn contractional ht decompression recorded by clockwise ptt paths and widespread strata overturning in thrust and fold structures which controlled the sedimentation in the adjacent foreland basin these unusual characteristics are interpreted to be a result of the succession of thrusting diapirism and extensional collapse antiformal stacking of syn metamorphic thrust sheets controlled the first stages of the foreland basin development diapirism was essentially responsible for the ht decompression and widespread strata overturning extensional doming was a result of late to post metamorphic collapse acting on the pre existing high amplitude dome diapirism and associated isothermal decompression metamorphism which constitute the essential difference between the montagne noire and ordinary frontal ridges in orogenic wedges were probably enhanced by a local partial melting of the upper to middle crust it is suggested that the occurrence of these phenomena in front of an orogenic wedge was related to local over thickening due to the superposition of an upper crustal antiformal stack on top of a lower crustal ramp anticline

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

use of the lattice parameter b 0 of dioctahedral illite muscovite for the characterization of p t gradients of incipient metamorphism the p t gradient or baric type of low grade metamorphic terranes can be characterized on the basis of cumulative frequency curves of the lattice parameter b0 of dioctahedral micas sassi and scolari 1974 which essentially reflects celadonite content and increases with pressure the method is here applied to illite muscovite of sub greenschist incipient metamorphism and low greenschist facies terranes from the marginal zones of the swedish caledonides swiss alps and venezuelan andes where the grade of metamorphism was determined on the basis of illite crystallinity

the tectono metamorphic evolution of the very low grade hangingwall constrains two stage gneiss dome formation in the montagne noire southern france the montagne noire in the southernmost french massif central is made of an ene elongated gneiss dome flanked by palaeozoic sedimentary rocks the tectonic evolution of the gneiss dome has generated controversy for more than half a century as a result a multitude of models have been proposed that invoke various tectonic regimes and exhumation mechanisms most of these models are based on data from the gneiss dome itself here new constraints on the dome evolution are provided based on a combination of very low grade petrology k ar geochronology field mapping and structural analysis of the palaeozoic western mont peyroux and faugeres units which constitute part of the southern hangingwall of the dome it is shown that southward directed variscan nappe thrusting d1 and a related medium p metamorphism m1 are only preserved in the area furthest away from the gneiss dome the regionally dominant pervasive tectono metamorphic event d2 m2 largely transposes d1 structures comprises a higher metamorphic thermal gradient than m1 transition low p and medium p metamorphic facies series and affected the rocks between c 309 and 300 ma post dating d1 m1 by more than 20 ma d2 related fabrics are refolded by d3 which in its turn is followed by dextral normal shearing along the basal shear zone of both units at c 297 ma in the western mont peyroux and faugeres units d2 m2 is largely synchronous with shearing along the southern dome margin between c 311 and 303 ma facilitating the emplacement of the gneiss dome into the upper crust d2 m2 also overlaps in time with granitic magmatism and migmatization in the zone axiale between c 314 and 306 ma and a related low p high t metamorphism at c 308 ma the shearing that accompanied the exhumation of the dome therefore was synchronous with a peak in temperature expressed by migmatization and intrusion of melts within the dome and also with the peak of metamorphism in the hangingwall both the intensity of d2 fabrics and the m2 metamorphic grade within the hangingwall decrease away from the gneiss dome with grades ranging from the anchizone epizone boundary to the diagenetic zone the related zonation of the pre d3 metamorphic field gradients paralleled the dome these observations indicate that d2 m2 is controlled by the exhumation of the zone axiale and suggest a coherent kinematic between the different crustal levels at some time during d2 m2 based on integration of these findings with regional geological constraints a two stage exhumation of the gneiss dome is proposed during a first stage between c 316 and 300 ma dome emplacement into the upper crust was controlled by dextral shear zones arranged in a pull apart like geometry the second stage from 300 ma onwards was characterized by northeast to northward extension with exhumation accommodated by north dipping detachments and hangingwall basin formation along the northeastern dome margin

viscous collision in channel explains double domes in metamorphic core complexes in hot orogens gneiss domes are a response to upper crustal stretching and lower crustal flow two dimensional thermal mechanical modeling shows that localization of extension in the upper crust triggers in the deep crust oppositely verging horizontal flows that converge beneath the extended region upon viscous collision both flowing regions rotate upward to form two upright domes of foliation double domes separated by a steep median high strain zone in such systems horizontal shortening in the infrastructure develops in an overall extensional setting dome material follows a complex depth dependent strain history from shearing in the deep crustal channel to contraction upon viscous collision in the median high strain zone to extension upon advection into the shallow crust this depth dependent strain history is likely a general feature of dome evolution and is arguably well preserved in double domes such as the montagne noire france and naxos greece gneiss domes