ionospheric effects during the total solar eclipse over southeast asia pacific on 9 march 2016 part 1 vertical movement of plasma layer and reduction in electron plasma density

the oldest uhp eclogites of the world age of uhp metamorphism nature of protoliths and tectonic implications coesite bearing eclogitic rocks from the pan african belt in northern mali were dated by multichronological methods rb sr sm nd and ar ar rb sr and sm nd isotope analyses on whole rock and mineral separates of an omphacite kyanite micaschist and a mafic eclogite yielded concordant ages of about 620 ma this is interpreted as the time of the eclogitisation which represents the oldest ultrahigh pressure uhp metamorphic event so far recorded in the continental crust the nearly identical rb sr and sm nd ages suggest very rapid exhumation as observed in many phanerozoic uhp rocks 40ar 39ar dating of phengites from two uhp micaschists gave much older ages of 1045 and 760 ma phengite from a quartzite collected from the same site yielded a plateau date of 623 3 ma which is in agreement with the rb sr and sm nd dates the two 40ar 39ar ages older than 625 ma testify once more the recurrent problem of excess ar in ultrahigh pressure phengites the occurrence of the mali uhp eclogites indicates that by the late precambrian the earth has cooled enough to sustain the formation and preservation of deeply subducted uhp metamorphic rocks the new ages of ca 620 ma also constrain the amalgamation in nw gondwana to have occurred in the latest proterozoic but not in the middle cambrian this is supported by several recent chronological data for the southern segment of the major suture zone in the dahomeyide orogenic belt

equatorial and low latitude ionosphere thermosphere system response to the space weather event of august 2005 1 the response of the equatorial and low latitude ionosphere thermosphere system to the geomagnetic storm during 23 26 august 2005 is investigated the study is carried out using the vertical total electron content vtec measured by gps receivers along the 77 78 e longitude and the o n2 ratio obtained from the global ultraviolet imager instrument on board the timed satellite the equatorial ionization anomaly eia shows a poleward latitudinal expansion on 24 august probably associated with an eastward prompt penetration electric field the equatorial and low latitudes show an increase in vtec during the main phase of the storm on 24 august the prompt penetration eastward electric field along with an increase in the o n2 ratio could be responsible for this observed positive phase the vtec variations on 24 august also reveal the signature of a large scale acoustic gravity wave traveling atmospheric disturbance propagating with a horizontal velocity of 750 m s suppression of the eia is observed during the storm recovery phase on 25 august which probably is associated with the westward disturbance dynamo electric field and the equatorward expansion of the neutral composition changes o n2 depletion

equatorial spread f instability conditions as determined from ionograms conditions of plasma irregularity or spread f generation under the rayleigh taylor mechanism in the nighttime equatorial ionosphere are examined from ionogram data registered over fortaleza 4 s 38 w mag dip lat 1 7 brazil for a one year period the results show that local ionospheric conditions such as the bottomside f region electron density scale length and the ion neutral collision frequency at the base of the layer at sunset hours determine the generation of the spread f irregularities over the equator in the post sunset hours

stratification of the f 2 layer observed in southeast asia this paper describes the latitudinal variation in f2 stratification balan and bailey 1995 as observed by a number of oblique and vertical ionosondes operating in southeast asia during 1997 stratification of the f2 layer was seen at dip latitudes from 4 s to 18 s on the southern side of the magnetic equator but did not occur at the closest reflection point to the magnetic equator dip latitude 2 3 n the observed transient cusp vertical ionosonde or additional nose oblique ionosonde was defined as an f3 layer or an f1 5 layer depending on whether it occurred above or below the layer which maintained continuity with the normal f2 layer peak within the zone of occurrence the transient layer was commonly seen as an f3 layer at reflection points closest to the magnetic equator but invariably as an f1 5 layer at reflection points farther from the magnetic equator these observations suggest that the distortion in the equatorial electron density profile associated with the phenomenon moved toward the base of the f2 layer as magnetic field lines descended with increasing latitude stratification of the f2 layer commenced at the same local time e g 0845 lt in november 1997 throughout the longitudinal range of coverage and was associated with a rapid rise in f2 layer height following sunrise the stratification ended at times varying from 1300 lt to sunset and was associated with a fall in the height of f2 peak electron density the region of maximum f2 layer stratification lay between the magnetic equator and the peak of the southern equatorial anomaly

an additional layer in the low latitude ionosphere in indian longitudes total electron content observations and modeling 1 the paper presents the observations and modeling of an additional layer in the low latitude ionosphere in indian longitudes the signatures of the additional layer are observed as ledges or humps between the equatorial ionization anomaly trough and crest eia in the latitudinal profiles of total electron content tec measured using a single ground based beacon receiver located at trivandrum 8 5 n 77 e dip 0 5 n in india the ground based ionograms also show the presence of the so called f 3 layer for a short duration corresponding to these signatures and the layer is found to drift upward to the topside ionosphere the study provides first observational evidence that the so called humps in the latitudinal variation of tec are nothing but the upward propagating f 3 layer this conclusion is supported by theoretical modeling using the sheffield university plasmasphere ionosphere model it is shown that upward exb drift and strong equatorward neutral wind perturbed by atmospheric waves can produce the humps in the latitudinal variation of tec through the reduction in the downward diffusion of ionization along geomagnetic field lines the model results also show that the f 3 layer drifts to the topside and forms topside ledges

additional stratifications in the equatorial f region at dawn and dusk during geomagnetic storms role of electrodynamics 1 the role of electrodynamics in producing additional stratifications in the equatorial f region f 3 layer at dawn and dusk during geomagnetic storms is discussed two cases of f 3 layer at dawn 0600 0730 lt on 5 october 2000 and 8 december 2000 and one case of f 3 layer at dusk 1600 1730 lt on 5 october 2000 are observed for the first time by the digital ionosonde at the equatorial station trivandrum 8 5 n 77 e dip 0 5 n in india the unusual f 3 layers occurred during the geomagnetic storms and are associated with southward turning of interplanetary magnetic field b z suggesting that eastward prompt penetration electric field could be the main cause of the f 3 layers the dawn f 3 layer on 5 october is modeled using the sheffield university plasmasphere ionosphere model by using the e x b drift estimated from the real height variation of the ionospheric peak during the morning period the model qualitatively reproduces the dawn f 3 layer while the existing f 2 layer rapidly drifts upward and forms the f 3 layer and topside ledge a new layer forming at lower heights develops into the normal f 2 layer

monitoring the daytime variations of equatorial ionospheric anomaly using ionex data and champ gps data a method which can invert the ionospheric electron content above the champ satellite is presented the daytime behavior of the equatorial ionospheric anomaly eia is monitored using the champ global positioning system data and the ionosphere map exchange format data supplied by the center for orbit determination in europe during the period at quiet geomagnetic conditions between november 7 and december 12 2003 results show that the plasma congregates and rises above the geomagnetic equator due to the daytime upward vertical drift during the early variations of eia after being lifted to higher altitudes the topside ionospheric equatorial plasma above the champ orbit over 400 km above the ground controlled mainly by the electromagnetic field starts to diffuse downward to higher latitudes along magnetic field lines and the double humped structure begins to appear in the topside ionosphere above the champ orbit however a single crest is still observed for the entire ionosphere above the ground and this single peak moves slightly to the winter hemisphere as a result of the transequatorial neutral wind with the continuous diffusion of the plasma the two crests also occur for the entire ionosphere at both sides of the geomagnetic equator

boron cycling by subducted lithosphere insights from diamondiferous tourmaline from the kokchetav ultrahigh pressure metamorphic belt abstract subduction of lithosphere involving surficial materials into the deep mantle is fundamental to the chemical evolution of the earth however the chemical evolution of the lithosphere during subduction to depth remains equivocal in order to identify materials subjected to geological processes near the surface and at depths in subduction zones we examined b and li isotopes behavior in a unique diamondiferous k rich tourmaline k tourmaline from the kokchetav ultrahigh pressure metamorphic belt the k tourmaline which includes microdiamonds in its core is enriched in 11b relative to 10b 11b 1 2 to 7 7 and 7li relative to 6li 7li 1 1 to 3 1 it is suggested that the k tourmaline crystallized at high pressure in the diamond stability field from a silicate melt generated at high pressure and temperature conditions of the kokchetav peak metamorphism the heavy isotope signature of this k tourmaline differs from that of ordinary na tourmalines in crustal rocks enriched in the light b isotope 11b 16 6 to 2 3 which experienced isotope fractionation through metamorphic dehydration reactions a possible source of the heavy b isotope signature is serpentine in the subducted lithospheric mantle serpentinization of the lithospheric mantle with enrichment of heavy b isotope can be produced by normal faulting at trench outer rise or trench slope regions followed by penetration of seawater into the lithospheric mantle serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy b isotope signature which was acquired during the serpentinization prior to subduction the fluids could ascend and cause partial melting of the overlying crustal layer and the resultant silicate melt could inherit the heavy b isotope signature the subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle

statistical analysis of an ionospheric parameter as a base for earthquake prediction 1 this paper is related to the use of ionospheric density variations to tentatively predict earthquakes the results of this statistical analysis are presented as a function of various parameters the ion density was recorded by the low altitude satellite demeter during more than 6 years and a search for anomalies was automatically conducted with the complete data set in a second time a software checked if each anomaly could correspond to an earthquake the search was conducted at less than 1500 km from the anomaly positions and until 15 days after the anomaly time the earthquakes have been classified depending on their magnitude depth and position below the sea or inland this attempt to predict earthquakes of course generates a lot of false alarms and wrong detections nevertheless it is shown that the number of good detections increases with the magnitude of the earthquakes in average the number of perturbations is higher the day of the earthquake and then smoothly decreases for the days before earthquakes below the sea are better detected there are seismic areas close to the south atlantic magnetic anomaly and at high latitudes where the number of natural perturbations is too important to expect a high number of good detections finally when there are several perturbations corresponding to a single earthquake it is possible to combine their positions to have a better estimation of the location of the future epicenter however uncertainties about the time and the magnitude are large

spatial distribution of ionization in the equatorial and low latitude ionosphere of the indian sector and its effect on the pierce point altitude for gps applications during low solar activity periods 1 the equatorial and low latitude ionosphere is characterized by dynamic changes in the spatial distribution of f region electron density the in situ density data from indian sross c2 satellite was used in conjunction with the international reference ionosphere iri to demonstrate how the median models have limitations to represent the spatial gradients in the equatorial and subtropical latitudes in the indian sector the ground based ionosonde data was used to derive the bottomside electron density profiles which were matched with iri to derive the complete f region electron density profile for different times to show the variability in the centroid of ionization mass distribution due to the equatorial plasma dynamics associated with appleton ionization anomaly the study brings out that a uniform ionospheric pierce point altitude cannot be assumed for gps applications in this sector however during low sunspot activity periods the gps derived total electron content tec using 2 2 grid point data indicates that spatial gradients in tec are not too significant in meridian transects and that the assumption of homogeneous distribution is valid for the conversion of slant to vertical tec even in the equatorial latitudes during solar minimum keeping this in view a qualitative study has been carried out on the possible variability in ionospheric pierce point altitude at representative subtropical latitude in the indian sector and the results are discussed in light of diurnal and seasonal features of the equatorial ionosphere

evidence for late proterozoic subduction from 700 myr old blueschists in china in a comprehensive review of the world s blueschists ernst1 noted an apparent absence of these high pressure low temperature rocks in the precambrian and ascribed it to a cooling of the earth in the phanerozoic eon as blueschists are thought to be formed in subduction zones the absence of precambrian blueschists has been adduced as evidence that plate tectonics did not operate on the early earth2 although this conclusion is not inevitable in that ancient mobile belts are more likely to have been obliterated than younger ones3 the presence of paired metamorphic belts of kyanite sillimanite and andalusite sillimanite grade in proterozoic gondwanaland supports the existence of a subducted slab but with ancient geothermal gradients too high to form blueschists along the convergent plate boundary4 5 on the other hand data from inclusions in african diamonds support the opposing view that archaean continental geotherms were similar to those of today6 here we present rb sr and k ar ages of 698 718 myr for phengitic mica from high pressure pelitic schists from the aksu region of china which are interleaved with blueschists we interpret these dates as representing the time of the blueschist facies metatmorphism suggesting that subduction was occurring in the late proterozoic

features of the f3 layer in the low latitude ionosphere at sunset the f 3 layer is a common feature within 10 degrees of the magnetic equatorial ionosphere in the daytime according to balan et al 1998 the f 3 layer occurs mainly during the morning noon period due to the combined effect of the upward e x b drift and the neutral wind that provides upward plasma drifts at and above the f 2 layer the f 3 layer occurrence rate is higher in summer and decreases with increasing solar activity in this study the characteristic of the sunset f 3 layer is first investigated using a solar cycle of ionosonde data 1995 2010 from the magnetic equatorial station at jicamarca and compared with the features derived from the four subtropical stations at sao luis fortaleza kwajalein and vanimo evidence shows that the local time distribution of the occurrence of the f 3 layer can extend to the postsunset time 1800 2100 local time the sunset f 3 layer has a strong seasonal dependence occurring mainly during the summertime unlike the daytime f 3 layer the occurrence of the sunset f 3 layer clearly increases and the virtual height of the bottom side of the f 3 layer statistically increases from 620 to 1000 km with increasing solar activity in addition the occurrence of the sunset f 3 layer at the other stations is much less than that at jicamarca these features of the dependence on the season solar activity and latitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and geomagnetic configuration

age and nature of eclogites in the huwan shear zone and the multi stage evolution of the qinling dabie sulu orogen central china abstract in situ la icpms u pb trace element and hf isotope data in zircon demonstrate a carboniferous age for eclogite facies metamorphism in siluro devonian protoliths in the huwan shear zone dabie mountains central china this age contrasts with the more prevailing triassic age for high to ultrahigh pressure hp to uhp metamorphism in the qinling dabie sulu orogen metamorphic zircon in two eclogite samples from sujiahe is characterized by low th u ratios small negative eu anomalies flat hree patterns and low 176 lu 177 hf ratios these geochemical signatures suggest that the zircon crystallized in the presence of garnet and in the absence of plagioclase feldspar furthermore temperatures of 655 and 638 c calculated using the ti content of zircon are consistent with their formation during eclogite facies metamorphism the weighted mean 206 pb 238 u age of 309 4 ma 2 for this zircon improves previous age estimates for eclogite facies metamorphism in the huwan shear zone ranging from 420 to 220 ma metamorphic zircon from one eclogite sample from hujiawan most likely formed during prograde metamorphism yields an equivalent age estimate of 312 11 ma magmatic zircon cores in the three samples yield ages for the magmatic protoliths of the eclogites ranging from 420 7 to 406 5 ma and post dating the middle paleozoic collision of the north china and the qinling terrain the zircon crystals in the three eclogite samples display a large variation of e hf t values of 4 9 to 21 3 the metamorphic zircon overgrowths show the same range of e hf t values as those of the inherited magmatic crystal interiors this suggests that the metamorphic zircon overgrowths may have formed by dissolution reprecipitation of pre existing magmatic zircon thereby preserving their original hf isotopic composition the high e hf t values suggest that the protoliths were derived from depleted mantle sources most likely paleotethyan oceanic crust while the low e hf t values are attributed to crustal contamination some eclogites in the huwan shear zone have a distinctive signature of continental crust most probably derived from the yangtze craton the coexistence of paleozoic oceanic crust and neoproterozoic continental crust with similar metamorphic ages in the huwan shear zone implies that paleozoic paleotethyan oceanic crust was produced within a marginal basin of the northern yangtze craton the opening of the paleo tethyan ocean was slightly younger than the collision of the north china craton and the qinling terrain during the late paleozoic in the qinling dabie sulu orogen subduction of the paleo tethyan oceanic crust and associated continental basement resulted in the 309 2 ma 2 eclogite facies metamorphism in the huwan shear zone the subsequent triassic continent continent collision led to the final coalescence of the yangtze and sino korean cratons amalgamation of the yangtze and north china cratons was therefore a multistage process extending over at least 200 ma

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

first simultaneous observations of f3 layer and e b drift in indian sector and modeling 1 although the basic mechanism of an additional stratification of the daytime equatorial f region called the f3 layer has been explained two observational aspects that remain not so clear are its summer winter differences and simultaneous occurrences on either side of the geomagnetic equator in this paper we address these two aspects using simultaneous observations of the f3 layer and vertical e b drift velocity made for the first time in an indian station gadanki 6 5 n mag lat during the low solar activity period 2008 2009 and making model computations using the sheffield university plasmasphere ionosphere model the observations confirm the frequent occurrence of the f3 layer in summer months compared to winter months the observations also reveal the occasional occurrence of clear and distinct f3 layer in winter although such a layer is frequent in summer in addition a threshold vertical plasma velocity involving the e b drift and neutral wind and its time integrated value are found to be important for the formation of the f3 layer the model results qualitatively reproduce the observations and show that irrespective of season the formation of the f3 layer is centered on that side of the equator where the equatorward neutral wind reduces the downward field aligned flow of plasma and the latitude band of the layer can extend to the opposite hemisphere especially when the vertical plasma velocity is large

neutral wind effect in producing a storm time ionospheric additional layer in the equatorial ionization anomaly region 1 a new type of the additional layer is predicted to occur in the low latitude f region ionosphere during evening hours of a major magnetic storm by using the coupled ncar thermosphere ionosphere electrodynamic general circulation model tiegcm and sheffield university plasmasphere ionosphere model supim runs during the major magnetic storm of 29 30 october 2003 we present a new type of additional layer which occurs at the equatorial ionization anomaly eia by a new physical mechanism this mechanism requires that storm time meridional neutral wind surges travel from high to low latitudes and cross into the opposite hemisphere the wind surges modify the field aligned plasma velocities in the eia regions significantly after uplift of the ionospheric layer by a penetration electric field and interact with the downward field aligned plasma velocities of the enhanced equatorial fountain the combined storm effects of the enhanced plasma fountain and the neutral wind surges result in plasma convergence in altitude and form the additional layers underneath the eia crests

magnetic conjugate observation of the f3 layer using the sealion ionosonde network 1 results from the meridional ionosonde network located in southeast asia sealion demonstrate the interesting nature of the f3 layer showing its generation mechanism ionograms obtained on 16 november 2004 and 31 march 2005 at chiang mai cmu geographic latitude 18 8 n geographic longitude 98 9 e and magnetic latitude 13 2 n chumphon cpn 10 7 n 99 4 e and 3 2 n and kototabang ktb 0 2 s 100 3 e and 10 1 s showed significant differences between cpn near the magnetic equator and cmu and ktb in the magnetic low latitude region the simultaneous magnetic conjugate observations of the f3 layer achieved using the sealion ionosonde network data showed clear dependences of the f3 layer on the magnetic latitude it is suggested that these magnetic latitude dependences of the f3 layer can be explained by considering the plasma diffusion effects along the magnetic field lines in the magnetic low latitude region

f3 layer during penetration electric field 1 the occurrence of an additional layer called f3 layer in the equatorial ionosphere at american indian and australian longitudes during the super double geomagnetic storm of 7 11 november 2004 is presented using observations and modeling the observations show the occurrence reoccurrence and quick ascent to the topside ionosphere of unusually strong f3 layer in australian longitude during the first super storm 8 november and in indian longitude during the second super storm 10 november all with large reductions in peak electron density nmax and total electron content gps tec the unusual f3 layers can arise mainly from unusually strong fluctuations in the daytime vertical e b drift as indicated by the observations and modeling in american longitude the strongest upward e b drift or eastward prompt penetration electric field ppef ever recorded at jicamarca produces unusually strong f3 layer in the afternoon hours 1400 1600 lt of ppef with large reductions in nmax and tec the layer also reappears in the following evening 1700 1800 lt owing to an unusually large downward drift at night when the drift is unusually upward and strong the f region splits into two layers

equatorial f region vertical plasma drifts seasonal and longitudinal asymmetries in the american sector longitudinal and seasonal asymmetries in the evening ionospheric f region plasma vertical drift v sub z enhancements between two longitudinally separated stations situated along the magnetic equator in the american sector are investigated under solar maximum conditions based on results obtained from the analysis of ionosonde data for these stations the two stations are huancayo peru and fortaleza brazil which have markedly different magnetic declination angles the observed asymmetries are interpreted using a detailed numerical simulation of the e and f region electrodynamic coupling process that takes into account also its asymmetry about the magnetic equator arising from the finite magnetic declination angle the results of the simulation show in agreement with observations that the occurrence time of the evening f region vertical drift prereversal peak and its seasonal variation at a station are controlled by the magnetic declination angle at that station which determines the seasonal variation of the sunset times and hence the integrated pedersen conductivity longitudinal gradient at its magnetic conjugate e layers the amplitude of the prereversal peak on the other hand undergoes the influence of the magnetic declination angle as well as of the thermospheric zonal wind component

determination of vertical plasma drift and meridional wind using the sheffield university plasmasphere ionosphere model and ionospheric data at equatorial and low latitudes in brazil summer solar minimum and maximum conditions the f region critical frequency fof2 and peak height hmf2 measured simultaneously at the equatorial location fortaleza 4 s 38 w magnetic latitude 3 5 s and at the low latitude location cachoeira paulista 22 s 45 w magnetic latitude 15 s are compared with their values calculated by the sheffield university plasmasphere ionosphere model supim to determine the vertical e b drift velocity at the equator and the magnetic meridional wind velocity over the two locations the calculated and observed values of fof2 are then matched at both fortaleza and cachoeira paulista to obtain the magnetic meridional winds over their respective conjugate locations to account for the observed fof2 diurnal variation pattern over cachoeira paulista it was found necessary to include a small source of ionization attributable to energetic particle precipitation in the south atlantic anomaly region the vertical drift velocity and magnetic meridional wind velocity derived for summer months during both solar minimum and solar maximum are compared with their values given by other published models while the diurnal variation of the modeled vertical drift velocity shows general agreement with the values based on jicamarca radar measurements the exception being during the sunset midnight period at solar maximum and between 2000 2300 lt at solar minimum the magnetic meridional wind shows significant differences with respect to the horizontal wind model 1990 hwm90 hedin et al 1991 during both solar minimum and solar maximum at fortaleza and at locations conjugate to fortaleza and cachoeira paulista

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

variations in the low and middle latitude topside ion concentration observed by dmsp during superstorm events 1 observations of the topside ion number density by the dmsp satellites on the dayside near 0930 lt and near dusk describe a characteristic evolution during the course of three superstorm events in november 2001 november 2003 and november 2004 density enhancements at middle latitudes and at the equator may be identified as separate features that may appear together but can evolve independently these characteristics are consistent with the action of both upward outward e b drifts and equatorward neutral winds and it is suggested that both f region drivers are required to reproduce the observed behavior on these occasions upward excursions of the e b drift at the equator may be short lived compared to the satellite orbit period of about 100 min but may also exist for longer periods under the influence of penetration fields and modified dynamo fields upward drifts at middle latitudes may be induced by meridional winds and by the high latitude convection pattern as it expands to latitudes as low as 40 degrees magnetic

daytime additional f layer stratification over low midlatitude station of the indian sector under geomagnetic disturbed conditions 1 in this paper the observations of additional f layer stratification are presented in a region which is situated at the outer edge of equatorial ionization anomaly eia zone the digital ionosonde data observed over delhi 28 6 n 77 2 e dip 42 44 n during march april 2001 has been used to carry out the present work the observational period was geomagnetically disturbed and represents the high solar activity phase of 23rd solar cycle the additional transient cusp is frequently observed in the considered months before the noon hours however in this paper only five prominent cases are presented from the analysis of ionograms it is observed that the transient additional cusp is formed between the pre existing f1 and f2 layer hence named as the cusp of f1 5 study reveals that the traveling atmospheric disturbances tads along with the vertical expansion of f layer provides the necessary condition for the existence of this transient feature the intensification of f1 layer along with increased altitude immediately after the disappearance of additional stratification remains one of the fascinating features of the present results the present investigation demonstrates that the daytime f1 and f2 region over low midlatitude station is strongly modulated by the passage of tids originating at high latitudes or by atmospheric disturbances of local origin during the high solar activity period the concurrent presence of tads and the associated disturbance composition appears to be plausible reason behind the present observations

equatorial plasma fountain and its effects over three locations evidence for an additional layer the f 3 layer the equatorial plasma fountain and equatorial anomaly in the ionospheres over jicamarca 77 w trivandrum 77 e and fortaleza 38 w are presented using the sheffield university plasmasphere ionosphere model under magnetically quiet equinoctial conditions at high solar activity the daytime plasma fountain and its effects in the regions outside the fountain lead to the formation of an additional layer the f3 layer at latitudes within about plus or minus 10 of the magnetic equator in each ionosphere the maximum plasma concentration of the f3 layer which occurs at about 550 km altitude becomes greater than that of the f2 layer for a short period of time before noon when the vertical e b drift is large within the f3 layer the plasma temperature decreases by as much as 100 k the ionograms recorded at fortaleza on january 15 1995 provide observational evidence for the development and decay of an f3 layer before noon the neutral wind which causes large north south asymmetries in the plasma fountain in each ionosphere during both daytime and nighttime becomes least effective during the prereversal strengthening of the upward drift during this time the plasma fountain is symmetrical with respect to the magnetic equator and rises to over 1200 km altitude at the equator with accompanying plasma density depletions in the bottomside of the underlying f region the north south asymmetries of the equatorial plasma fountain and equatorial anomaly are more strongly dependent upon the displacement of the geomagnetic and geographic equators jicamarca and trivandrum than on the magnetic declination angle fortaleza

storm enhanced plasma density sed features auroral and polar plasma enhancements and rising topside bubbles of the 31 march 2001 superstorm 1 this study focuses on the 31 march 2001 superstorm s evening and nighttime sectors we specified forward fountain circulation and equatorial ionization anomaly eia storm enhanced density sed plume plasma flows auroral zones polar cap regions and traveling ionospheric disturbances tids these permitted analyzing low latitude plasma structures and middle and high latitude plasma buildups results reveal significant low latitude plasma structuring around ancon due to topside rising bubbles during the initial phase under disturbance conditions the deep equatorial plasma depletion appearing over the pacific during the main phase is an eia trough bubble structure topside bubbles and tid related drift perturbations structured sed plume plasma plasma distribution maximized when tids were in phase with fountain circulation and sed plume plasma flows and equatorward wind surges maintained high plasma densities plasma density and plasma flow measurements demonstrate the sed plume plasma s poleward migration through the auroral zone into the polar region and the maintenance and increase of auroral and polar enhancements forming a polar tongue of ionization toi our results contradict previous studies on this superstorm reporting the suppression of bubble formation over ancon and the absence of toi and explaining the development of equatorial depletion with no e b drift action our results oppose the current hypothesis that plasma enhancements are transported over many hours into the polar region indeed sed plume plasma produced by plasmaspheric detachment processes creates multiple downward plasma flows stretching from the midlatitude trough s equatorward edge to the polar cap region that in turn create plasma buildups at various latitudes where flow stagnates

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

features of additional stratification in ionospheric f2 layer observed for half a solar cycle over indian low latitudes 1 the features of the additional stratification in the ionospheric f2 layer often referred to as the f3 layer observed over an indian low latitude station waltair 17 7 n 83 3 e magnetic latitude mag lat 8 2 n during the period 1997 2003 are presented along with the data from two other indian stations the observations grossly confirm those reported earlier in the occurrence and seasonal variability of the f3 layer from an analysis of half a solar cycle ionosonde data 1997 2003 it is observed that the layer appeared more frequently during the summer solstice months of low solar activity period and persisted for longer durations during this season compared with equinox and winter solstice the best stratification is seen between 10 12 hours ist the occurrence of the f3 layer does not seem to depend on magnetic activity but the percentage of occurrence decreased with increasing solar activity the solar activity dependence over waltair confirms the model predictions of balan et al 1998 that the layer becomes less distinct and less frequent as solar activity increases the ionosonde data for the same period 1997 2003 from an equatorial station trivandrum 8 4 n 76 9 e mag lat 0 47 n and another low latitude station shar 14 n 80 e mag lat 6 8 n are also analyzed with a view to examine the effect of the equatorial plasma dynamics on the occurrence of such events

an investigation of the northern hemisphere midlatitude nighttime plasma density enhancements and their relations to the midlatitude nighttime trough during summer this study has utilized regional surface maps and field aligned latitudinal profiles derived from multiinstrument dmsp f15 data it investigates northern midlatitude plasma enhancements in the nighttime topside ionosphere during summer and their relation to the midlatitude heavy ion stagnation trough the tracked midlatitude summer enhancements showed significant longitudinal variations their best development occurred in the 50 n 60 n 110 e 170 e geographic region proven by coupled thermosphere ionosphere plasmasphere wind velocity simulations equatorward winds were strongest there this region is the northern hemisphere equivalent of the weddell sea anomalys wsa locality there northern summer plasma enhancements resembled the nighttime wsa a southern summer equinoctial phenomenon and thus were named as wsa like feature their plasma density increased mainly owing to the mechanical or direct effects of the equatorward winds however as results show the wsa like feature was an ordinary northern midlatitude nighttime enhancement occurring in summer this was further confirmed by the wsa like features relation to the trough and by the troughs movement over the northern hemisphere the summer trough appeared at 62 461 2 93 n geomagnetic poleward of the wsa like feature and other midlatitude plasma enhancements and moved equatorward with a rate of 0 097 0 04 n nt when magnetic activity increased as our previous wsa investigation indicates the southern summer trough develops at lower latitudes at 47 1564 2 16 s equatorward of the nighttime wsa and moves poleward with a rate of 0 0497 0 003 s nt with increasing magnetic activity under the combined influence of the nighttime wsa and south atlantic magnetic anomaly copyright 2009 by the american geophysical union

on the occurrence and boron isotopic composition of tourmaline in ultra high pressure metamorphic rocks abstract the extensive p t stability and the high chemical variability of tourmaline tur together with its common occurrence in metasediments proves its high potential for petrological and isotope geochemical studies on fluid rock interaction in subduction and collision related rocks this paper reviews the occurrence major element chemistry and boron isotopic composition of tur in high and ultrahigh pressure metamorphic uhpm rocks in addition it presents a new discovery of coesite bearing tur schorl from the erzgebirge germany as well as tur dravite related to the retrograde history of coesite and diamond bearing rocks from the erzgebirge and the kokchetav massif kazakhstan the scarce data on worldwide occurrences of u hpm tur reveal a high occupation of the crystallographic x site dominated by na and the possible presence of excess b with little further distinctiveness in its major element composition when compared with tur from medium grade rocks high k 2 o contents in tur are probably not related to uhp growth or equilibration the b isotopic composition of u hpm tur ranges in 11 b from 16 to 1 with many samples in or below the range of continental crust in contrast tur formed during retrograde fluid influx typically shows high 11 b values up to 28 suggesting heavy b fluids infiltrating the exhuming u hpm units coesite inclusions in tur characterized by raman spectroscopy are regarded as the best indicator for its uhp stability supplementary material analytical methods tourmaline compositions and boron isotope values are available at http www geolsoc org uk sup18354

permo triassic collision subduction zone metamorphism and tectonic exhumation along the east asian continental margin abstractconvergent plate motion at 320 210 ma generated the tongbai dabie sulu east central china imjingang gyeonggi central korea renge suo southwestern japan sikhote alin orogen along the paleo pacific edge of cratonal asia this amalgamated belt reflects collision between the sino korean and yangtze cratons on the sw portion and accretion of outboard oceanic arcs sialic fragments against the ne margin subducted proterozoic paleozoic continental and oceanic crustal complexes underwent high and ultrahigh pressure metamorphism at low to moderate temperatures tectonic slices of sialic crust episodically disengaged from the downgoing plate and driven by buoyancy ascended rapidly to midcrustal levels from depths exceeding 90 200 km after continental collision in east central china plus or minus korea and from 30 50 km after arrival of far traveled oceanic terranes in sw japan and the russian far east on achieving neutral buoyancy and stalling out at 10 20 km depth later doming gravitation

recycling of crustal materials through study of ultrahigh pressure minerals in collisional orogens ophiolites and mantle xenoliths a review abstract newly recognized occurrences of ultrahigh pressure uh p minerals including diamonds in ultrahigh temperature uh t felsic granulites of orogenic belts in chromitites associated with ophiolitic complexes and in mantle xenoliths suggest the recycling of crustal materials through deep subduction mantle upwelling and return to the earth s surface this circulation process is supported by crust derived mineral inclusions in deep seated zircons chromites and diamonds from collision type orogens from eclogitic xenoliths in kimberlites and from chromitities of several alpine himalayan and polar ural ophiolites some of these minerals contain low atomic number elements typified by crustal isotopic signatures ophiolite type diamonds in placer deposits and as inclusions in chromitites together with numerous highly reduced minerals and alloys appear to have formed near the mantle transition zone in addition to ringwoodite and inferred stishovite a number of nanometric minerals have been identified as inclusions employing state of the art analytical tools reconstitution of now exsolved precursor uh p phases and recognition of subtle decompression microstructures produced during exhumation reflect earlier uh p conditions for example tibetan chromites containing exsolution lamellae of coesite diopside suggest that the original chromitites formed at p 9 10 gpa at depths of 250 300 km the precursor phase most likely had a ca ferrite or a ca titanite structure both are polymorphs of chromite and at 2000 c would have formed at minimum pressures of p 12 5 or 20 gpa respectively some podiform chromitites and host peridotites contain rare minerals of undoubted crustal origin including zircon feldspars garnet kyanite andalusite quartz and rutile the zircons possess much older u pb ages than the time of ophiolite formation these uh p mineral bearing chromitite hosts evidently had a deep seated evolution prior to extensional mantle upwelling and partial melting at shallow depths to form the overlying ophiolite complexes these new findings together with stable isotopic and inclusion characteristics of diamonds provide compelling evidence for profound underflow of both oceanic and continental lithosphere recycling of surface organic carbon into the lower mantle and ascent to the earth s surface through mantle upwelling intensified study of uh p granulite facies lower crustal basement and ophiolitic chromitites should allow a better understanding of the geodynamics of subduction and crustal cycling

motions of the equatorial ionization anomaly crests imaged by formosat 3 cosmic 1 the equatorial ionization anomaly eia structures and evolutions are imaged using radio occultation observation of the newly launched formosat 3 cosmic f3 c satellite constellation three dimensional ionospheric images provide unprecedented detail of the eia structure globally this paper presents images of the eia structures during july august 2006 and discusses the development and subsidence of the eia clear seasonal asymmetries in both ionospheric electron density and layer height are observed two dimensional cross section maps at a meridian provide dynamic variations and motions of the northern and southern eia crests results suggest that in addition to the asymmetric neutral composition effect interactions between the summer to winter transequatorial neutral winds and strength of the equatorial plasma fountain effect play important roles in producing asymmetric development of the eia crests as imaged by the f3 c

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

traveling ionospheric disturbances and their relations to storm enhanced density features and plasma density irregularities in the local evening and nighttime hours of the halloween superstorms of 29 31 october 2003 1 this study focuses on the local evening or nighttime hours of the halloween superstorms its database containing multi instrument defense meteorological satellite program data plus ionosonde and magnetometer data allowed us to investigate the various plasma density features developed and the impact of traveling ionospheric disturbances tids drift perturbations and south atlantic magnetic anomaly sama effects on them we identified the midlatitude trough some topside bubbles the equatorial ionization anomaly eia and some storm enhanced density sed features results reveal that these features underlying vertical plasma flows became enhanced degraded when they were in the same opposite direction as the field aligned flows associated with a tid demonstrated with some coupled thermosphere ionosphere plasmasphere simulated wind vector maps high low plasma densities were maintained by equatorward poleward winds we observed some descending 600 m s bubbles with increased temperatures 4500 k due to their fast poleward movement 1 4 km s structuring some nearby sed features in the sama region and some low latitude plasma in the australian sector during the second superstorm s main phase 30 october 2003 a rising bubble with increased temperatures 5000 k due to the sama s energetic electrons further depleted the eia trough this observation contradicts a current interpretation of this depleted eia trough as bubble at the time of prereversal enhancement 2300 ut on 30 october some extremely large sed features 85 104 ions cm3 developed 30 n geomagnetic latitude around the symmetrical eia over brazil this scenario created a symmetrical plasma density profile contradicting some current speculations on the eia s asymmetry and its southern crest s displacement to higher latitudes over brazil indeed a sed feature appeared at higher latitudes 35 s geographic latitude

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

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

atypical nighttime spread f structure observed near the southern crest of the ionospheric equatorial ionization anomaly 1 an atypical nighttime spread f structure is observed on ionograms at or above the f2 trace near the crest of the ionospheric equatorial ionization anomaly eia region this ionospheric atypical spread f phenomenon was observed using two closed spaced 115 km ionospheric soundings stations located in sao jose dos campos 23 21 s 45 97 w and cachoeira paulista 22 70 s 45 01 w brazil in a low latitude station near the southern crest of the eia region during nighttime low solar activity and quiet geomagnetic conditions this structure in the initial phase appears in the ionogram as a faint spread f trace above or at the f2 layer peak height after a few minutes it develops into a strong spread f trace and afterwards it moves to altitudes below the f2 layer peak heights finally the atypical nighttime f layer trace structure may remain for a while between the f layer bottom side and peak height or can move to an altitude above the f layer peak height and then it disappears in order to have a comprehensive view of the ionospheric environment characterizing the phenomenon under study complementary data from six gps station were used to investigate the ionosphere environment conditions during both events the six gps stations used in this study are distributed from near the equatorial region to low latitudes and provide evidence that the atypical nighttime spread f structures are not related with large scale equatorial irregularities plasma bubbles

observations of ionospheric f layer quadruple stratification near equatorial region this paper presents and discusses the occurrence of f layer quadruple stratification stf 1 stf 2 stf 3 and stf 4 during southern hemisphere winter season june july and august 2002 and high solar activity condition which was observed at palmas 10 3 s 48 3 w dip latitude 5 5 s near equatorial region brazilian sector this is the first time that the formation of f layer quadruple stratification stf 1 stf 2 stf 3 and stf 4 has been reported in the south american sector the stf 4 has a short lifetime compared with triple stratification f3 layer and it is antecedent and followed by triple f3 layer stratification

on the equatorial anomaly of the ionospheric total electron content near the northern anomaly crest region daily contour charts of the ionospheric total electron content in latitude versus local time coordinates have been used to study the behavior of the development of the equatorial anomaly around the northern anomaly crest region the daily development of the equatorial anomaly shows quite large day to day variabilities not only on magnetically disturbed days but also on quiet days the daily maximum anomaly crest moves poleward as the magnitude of the total electron content of the daily maximum anomaly crest increases the increase of the equatorial electrojet strength also results in a poleward movement of the anomaly crest no significant correlation exists between the anomaly crest and the magnetic ital ap index the monthly mean diurnal development of the equatorial anomaly shows a remarkable seasonal difference with the anomaly largest in equinoxes and slightly larger in winter than in summer copyright american geophysical union 1989

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

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

an empirical model of the occurrence of an additional layer in the ionosphere from the occultation technique preliminary results about 8 year electron density profile edp data from the cosmic formosat 3 satellites radio occultation technique were used to investigate the additional stratification of the f2 the so called f3 layer layer over the equatorial and low latitude ionosphere on a global scale for both the bottomside and topside ionosphere the f3 layer was recognized through the altitude differential profile featured by two maxima existing from the selected edp profile there were 37 000 bottomside and 25 000 topside cases of f3 layer selected out of 1 27 million occultation events at equatorial and low latitude areas during the period of april 2006 to august 2014 the statistical results for the bottomside ionosphere resemble that reported in zhao et al 2011a while in the topside the highest occurrence of f3 layer shows a 3 4 h delay depending on the altitude range of the stratification the magnetic latitude distribution shows different dependence with a tendency to form a single crest toward high altitude also the seasonal variation is weaker in the topside ionosphere compared to the bottomside one especially in the high altitude then we build up an empirical model of the f3 layer occurrence using the bottomside statistics based on empirical orthogonal function eof decomposition as it gets the inherent characters inside the data set and converges quickly the model well grasps the main features of the f3 occurrence e g the f3 occurrence s sensitivity on the magnetic latitude further in order to accommodate the ground observation a corrected factor was introduced as f3 layer is an important phenomenon in the low latitude ionosphere we have made an attempt to describe its feature with a consecutive function although future work needs to be done for an overall expression of this structure

diamond inclusions in garnets from metamorphic rocks a new environment for diamond formation diamonds commonly occur in kimberlites lamproites and alluvial sediments derived from these rocks more recently diamonds or their graphite pseudomorphs have been discovered in ultramafic massifs1 and picrites2 here we report the occurrence of diamonds in situ in crustal rocks highly retrograded high pressure metamorphic garnet pyroxene and pyroxene carbonate garnet rocks biotite gneisses and schists from the kokchetav massif northern kazakhstan ussr the diamonds are cubo octahedral averaging 12 m in size and occur in zircons and with euhedral graphite as inclusions in unzoned garnets we believe that the zircon and garnet matrices protected these diamonds from retrogressive transformation to graphite mica rutile titanite clinopyroxene kyanite and zircon also occur as inclusions in garnet often intergrown with the diamonds equilibration relations of inclusions and host garnets indicate that both diamonds and graphite crystallized from a fluid phase under static conditions at pressures of 40 kbar and temperatures 900 1 000 c

possible gyre gyre interaction in the pacific ocean the subtropical anticyclonic gyres of the north and south pacific ocean are among the largest circulation systems found in the ocean the gyres contain the warm waters of the warm water sphere1 2 and the rotation of these water masses is subject to low frequency variations3 the presence in these gyres of baroclinic rossby waves with periods of many years has been documented4 5 and this seems to be sufficient proof that the gyres undergo vacillations using sea level data we demonstrate here that the subtropical gyres of the north and south pacific oscillate with a period of about 4 years and that these oscillations are probably induced by the major el nino events

global characteristics of occurrence of an additional layer in the ionosphere observed by cosmic formosat 3 global observations of electron density profile edp from the cosmic formosat 3 satellites were used to investigate for the first time the additional stratification of the f2 layer over the equatorial ionosphere on a global scale which is called f3 layer the f3 layer in edp was recognized through the altitude differential profile featured by two maxima existing from 220 km to the peak height of the electron density there were similar to 9 400 cases of f3 layer selected out of similar to 448 000 occultation events at low and equatorial areas during the period of april 2006 september 2010 statistical results show that the highest occurrence of f3 layer appears at dip latitude 7 similar to 8 degrees 7 similar to 8 degrees for northern southern hemisphere and is more pronounced during summer months at 10 00 14 00 lt the occurrence also has a clear longitude dependence during boreal summer with relatively higher occurrence at 80 similar to 100 degrees 20 similar to 20 degrees 80 similar to 120 degrees and 160 similar to 170 degrees longitudes that is possibly associated with the wavenumber 3 diurnal tide de3 the results support the principle of the f3 layer proposed by balan et al 1998 which in turn validate the accuracy of the retrieval of the cosmic edp data citation zhao b w wan x yue l liu z ren m he and j liu 2011 global characteristics of occurrence of an additional layer in the ionosphere observed by cosmic formosat 3 geophys res lett 38 l02101 doi 10 1029 2010gl045744

late neoproterozoic paleomagnetic results from the sugetbrak formation of the aksu area tarim basin nw china and their implications to paleogeographic reconstructions and the snowball earth hypothesis abstract in order to better constrain the neoproterozoic paleogeographic reconstruction of continents and to improve the understanding of the snowball earth hypothesis paleomagnetic investigations were carried out in the aksu area of the northwestern tarim basin forty eight sites of samples were collected from the sugetbrak and chigebrak formations twenty four sites of sandstone and volcanic rock from the sugetbrak formation revealed stable characteristic remanent components chrm isolated between 500 and 680 c the computed magnetic directions from these components are consistent and significantly distinguished from those of younger ages both normal and reverse polarities have been observed and a positive fold test is revealed after bedding corrections at 95 confidence level anisotropy of magnetic susceptibility measurements shows primary sedimentary fabrics with weak anisotropy degrees a paleomagnetic pole is calculated at 19 1 n 149 7 e k 11 2 a95 9 3 with n 24 yielding a paleolatitude of 27 n for the sampling area the chemo stratigraphic correlation of this section with reference ones reveals an average age of 595 ma a new paleogeographic reconstruction has been attempted showing general low paleolatitude positions for the australia south china and tarim blocks at about 600 ma this observation provides new evidences for the snowball earth hypothesis