sounding of the topside ionosphere plasmasphere based on gps measurements from champ initial results 1 beside the gps radio occultation measurements of the troposphere and ionosphere the champ satellite tracks presently up to 8 gps satellites simultaneously for navigation the received dual frequency gps signals provide valuable information on the ionization state of the topside ionosphere and plasmasphere this paper briefly describes a new developed model assisted technique to improve the three dimensional electron density estimation above the champ orbit from these gps measurements application of this assimilation algorithm provides a 2 d electron density slice of the ionosphere plasmasphere system within the champ orbit plane from the champ altitude up to gps orbit heights we estimate the accuracy of the gps tec calibration and perform a first validation by comparing the retrieved electron density of the ionosphere plasmasphere slice at champ altitude to simultaneous electron density measurements of the langmuir probe onboard champ

fission track analysis of the late cenozoic vertical kinematics of continental pacific crust south island new zealand during the late cenozoic the pacific plate has been converging obliquely with the australia plate in south island new zealand a result of this convergence has been the growth of a major mountain range the southern alps at the leading edge of the pacific plate the results of fission track analysis of 140 samples from 13 transects across the alps reported here establish the late cenozoic vertical kinematics amount age and rate of rock uplift of the pacific crust underlying the alps the late cenozoic rock uplift of the pacific crust is asymmetrical with respect to the alpine fault being a maximum 19 km immediately east of the central part of the fault with lesser values at the eastern 3 km northern 10 km and southern 8 km extremities of the alps the age of the start of rock uplift varies spatially across the southern alps the earliest indications from fission track analysis being at 8 ma at the southern end of the alps decreasing to 5 ma at the northern end and 3 ma along the southeastern margin this age variation reflects the longer time over which the southern parts of the alps have been in collision the rate of propagation of rock uplift southeastward into the pacific plate has been 30 mm yr nearly 4 times the late cenozoic average rate of convergence normal to the plate boundary late cenozoic mean rock uplift rates range from a maximum of 2 8 mm yr at the alpine fault to a minimum of 1 0 mm yr in the east and have been sustained for periods of 3 8 m y accompanying denudation has exhumed amphibolite grade rocks immediately east of the alpine fault the rock uplift has been controlled by oblique slip displacement on the alpine fault a continental crustal section at least 19 km thick has been uplifted on the alpine fault comparison of the late cenozoic mean rock uplift rates with uplift rates derived from reset zircon data 2 10 mm yr near the alpine fault shows that uplift has accelerated over time but only significantly since 1 3 0 3 ma the amount of mesozoic uplift ranged from minimal amounts north of arthur s pass to 3 km near mount cook to 10 km in the south at lake wanaka

provenance analysis using raman spectroscopy of carbonaceous material a case study in the southern alps of new zealand detrital provenance analyses in orogenic settings in which sediments are collected at the outlet of a catchment have become an important tool to estimate how erosion varies in space and time here we present how raman spectroscopy on carbonaceous material rscm can be used for provenance analysis rscm provides an estimate of the peak temperature rscm t experienced during metamorphism we show that we can infer modern erosion patterns in a catchment by combining new measurements on detrital sands with previously acquired bedrock data we focus on the whataroa catchment in the southern alps of new zealand and exploit the metamorphic gradient that runs parallel to the main drainage direction to account for potential sampling biases we also quantify abrasion properties using flume experiments and measure the total organic carbon content in the bedrock that produced the collected sands finally we integrate these parameters into a mass conservative model our results first demonstrate that rscm t can be used for detrital studies second we find that spatial variations in tracer concentration and erosion have a first order control on the rscm t distributions even though our flume experiments reveal that weak lithologies produce substantially more fine particles than do more durable lithologies this result implies that sand specimens are good proxies for mapping spatial variations in erosion when the bedrock concentration of the target mineral is quantified the modeling suggests that highest present day erosion rates in whataroa catchment are not situated at the range front but around 10 km into the mountain belt

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

southern hemisphere ionosphere and plasmasphere response to the interplanetary shock event of 29 31 october 2003 1 we analyze the effects on the southern hemisphere ionosphere and plasmasphere due to the 29 31 october 2003 geomagnetic storms the so called series of halloween storms solar wind data from ace and ionospheric data from the gps global position system ground and leo low earth orbit receivers the topex poseidon altimeter the image fuv camera and the dmsp drift meter are used to understand the ionospheric dynamics as a function of the storm phase the detailed structure of the ionosphere has been obtained using tomographic reconstruction applied to data from both ground and space based gps receivers the tomographic approach using leo observations of signals received from gps satellites above the leo s horizon allows us to investigate the topside ionospheric and plasmaspheric density distribution in more detail than can be obtained using ground based gps receivers this is because with ground based receivers the higher topside ionosphere and plasmasphere contribute only a small fraction to the total electron content tec and so the measurements are dominated by the ionospheric structure at the f2 peak in contrast the australian leo satellite fedsat which has been used for this study orbits at 800 km altitude well above the f2 peak and hence the tec measured is primarily due to the upper topside ionosphere and plasmasphere this paper presents the tomographically reconstructed topside ionosphere and plasmasphere electron density distributions using leo observations the temporal and regional maps of tec and the image fuv data show that the storm that commenced on 29 october dramatically decreased the plasma density in the southern hemisphere middle and high latitudes the region remained depleted of plasma for more than 24 hours until 31 october when the second severe storm began topex poseidon data shows a daytime localized density enhancement occurred above the middle of the pacific ocean these results show large interhemispheric and longitudinally narrow storm time structure in the ionosphere and topside ionosphere plasmasphere

evaluation of the topex poseidon dual frequency ionosphere correction the nasa altimeter on board topex poseidon exploits the difference in the delays of the ku and c band radar pulses to estimate an ionosphere correction to the range measurement the dependence of the ionosphere correction on ocean and satellite parameters is less than 1 cm the standard deviation of the 1 s averaged ionosphere correction depends on the height of the ocean waves and ranges from 5 to 14 mm the accuracy of the ionosphere correction is better than 1 cm at the 1 confidence level the ionosphere correction should be averaged over 140 km 20 s along track in order to minimize its noise without sacrificing its accuracy ionosphere models must achieve an independent sample spacing of 900 km or less in order to allow a single frequency altimeter to have an ionosphere correction comparable in accuracy to that of the nasa dual frequency altimeter

unusual topside ionospheric density response to the november 2003 superstorm 1 we use observations from a variety of different ground and space based instruments including ionosonde ground and space based global positioning system gps receivers magnetometers and solar wind data from the advanced composition explorer ace to examine the response of the ionospheric f2 layer height during the november 2003 superstorm we found that the topside ionosphere responded unusually to the 20 november 2003 severe storm compared to behavior observed in a number of previous storms while ground based gps receivers observed a large enhancement in dayside tec the low earth orbiting 400 km champ satellite did not show any sign of dayside tec enhancement the real time vertical density profiles constructed from ground based gps tec using a tomographic reconstruction technique clearly revealed that the ionospheric f2 layer peak height had been depressed down to lower altitudes ionospheric f layer peak height hmf2 from the nearby ionosonde stations over europe also showed that the dayside f2 layer peak height was below 350 km which is below the orbiting height of champ the vertical e b drift estimated from ground based magnetometer equatorial electrojet delta h showed strong dayside downward drifts which may be due to the ionospheric disturbance dynamo electric field produced by the large amount of energy dissipation into high latitude regions this storm demonstrates that data from leo satellites varies widely among different superstorms

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

last glacial maximum climate in new zealand inferred from a modelled southern alps icefield abstract we present a simulation of the new zealand southern alps icefield at the last glacial maximum lgm c 30 000 20 000 calendar years ago ka in an attempt to constrain the climate of that period we use a 500 m resolution ice sheet model parameterised using empirical glaciological climatological and geological data specific to the model domain to simulate the entire southern alps icefield we find that an lgm cooling of at least 6 6 5 c is necessary to bring about valley glaciers that extend beyond the mountains however climate topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain and in order to remain within geologically reconstructed lgm limits we find that the lgm cooling was most likely associated with a precipitation regime up to 25 drier than today wetter than present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence these results perhaps indicate that either the westerly air masses affecting new zealand during the lgm were drier than today or that they were weaker or zonally displaced with respect to present

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

reflection coefficients at pore fluid contacts as a function of offset it has been recognized for some time that seismic amplitude variations with offset contain lithologic and pore fluid information however the exact formulas for plane wave reflection coefficients are not easily interpreted in terms of the effects expected from classes of geologic models for fluid contacts within a rock unit which may show up as flat spots in seismic data simplified approximate formulas can be derived to predict reflection coefficients for compressional p and shear s waves the formulas derived in this note predict under the assumption that changes in pore fluid do not affect the elastic properties of the rock matrix that the p and s reflection coefficients from a gas brine gas oil or oil brine contact increase monotonically with offset and that for a gas brine contact the ratio of the two coefficients is sensitive to gas saturation

longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics 1 accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time season and magnetic activity is required to improve the operation of space based navigation and communication systems the vertical density distribution especially at low and equatorial latitudes is governed by the equatorial electrodynamics that produces a vertical driving force the vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground based global positioning system gps total electron content tec similarly the vertical drift which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low midlatitude region can be estimated using ground magnetometer observations we present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes the east african and west south american sectors chains of gps stations in the east african and west south american longitudinal sectors covering the equatorial anomaly region of meridian 37 e and 290 e respectively are used to reconstruct the vertical density distribution similarly magnetometer sites of african meridian b field education and research amber and intermagnet for the east african sector and south american meridional b field array samba and low latitude ionospheric sensor network lisn are used to estimate the vertical drift velocity at two distinct longitudes the comparison between the reconstructed and jicamarca incoherent scatter radar isr measured density profiles shows excellent agreement demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes similarly the comparison between magnetometer estimated vertical drift and other independent drift observation such as from vefi onboard communication navigation outage forecasting system c nofs satellite and julia radar is equally promising the observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences especially the equatorial anomaly peaks expand to higher latitudes more in american sector than the african sector indicating that the vertical drift in the american sector is stronger than the african sector

negative ionospheric storm coincident with de 1 observed thermospheric disturbance on october 14 1981 the de 1 far ultraviolet fuv imaging instrument recorded a large thermospheric disturbance over europe and russia on october 14 1981 during a geomagnetic storm commencing near the end of the previous day the disturbance is quantified in terms of o n2 the column density ratio referenced to a fixed depth in n2 the ratio is derived from de 1 dayglow observations with a filter whose signal transmission is dominated by o i 130 4 nm emission within the disturbed region o n2 is less than that in surrounding regions with minimum values being more than a factor of 2 smaller than undisturbed values images of o n2 are compared to ground based ionosonde data from 13 sites some within and others outside of the disturbed region the data are in the form of nmax the maximum electron density which in the presence of an f2 layer is equivalent to nmf2 the data exhibit negative ionospheric storm effects reduced nmax within the disturbed region and normal behavior elsewhere the degree of correlation between o n2 and nmax suggests that the approximate geographical extent of dayside regions experiencing negative ionospheric storm effects can be determined from global fuv imaging of the disturbed and surrounding regions the analysis is extended to the following day to address the recovery of the disturbed region the o n2 ratio has returned to undisturbed values except in a smaller disturbance region containing weak reductions in o n2 this is either a remnant of the strong disturbance from the day before or a newly formed disturbance from substorm activity several hours prior to the new observations only the ionosonde sites within this region recorded values of nmax below their monthly median values

the influence of rock mass strength on glacial valley cross profile morphometry a case study from the southern alps new zealand the erosional morphology in the vicinity of the main divide of the southern alps and fiordland new zealand appears to be a product of the interaction between alpine fault induced tectonic processes rock mass strength of the uplifted and eroded bedrock and the processes acting to denude the developing mountain landscape the magnitude of the effects of glacial erosion on the landscape is directly controlled by the size and physical properties of the glaciers whilst the form of the trough is a direct consequence of the rock mass strength rms properties of the slope rock realistic models of development of the cross profile shape of glacial valleys must take into consideration the rms properties of the eroded substrate

ionospheric response at conjugate locations during the 7 8 september 2017 geomagnetic storm over the europe african longitude sector this paper focuses on unique aspects of the ionospheric response at conjugate locations over europe and south africa during the 7 8 september 2017 geomagnetic storm including the role of the bottomside and topside ionosphere and plasmasphere in influencing electron density changes analysis of total electron content tec on 7 september 2017 shows that for a pair of geomagnetically conjugate locations positive storm effect was observed reaching about 65 when benchmarked on the monthly median tec variability in the northern hemisphere while the southern hemisphere remained within the quiet time variability threshold of 40 over the investigated locations the southern hemisphere midlatitudes showed positive tec deviations that were in most cases twice the comparative response level in the northern hemisphere on the 8 september 2017 during the storm main phase on 8 september 2017 we have obtained an interesting result of ionosonde maximum electron density of the f2 layer and tec derived from global navigation satellite system gnss observations showing different ionospheric responses over the same midlatitude location in the northern hemisphere in situ electron density measurements from swarm satellite aided by bottomside ionosonde derived tec up to the maximum height of the f2 layer hmf2 revealed that the bottomside and topside ionosphere as well as plasmasphere electron content contributions to overall gnss derived tec were different in both hemispheres especially for 8 september 2017 during the storm main phase the differences in hemispheric response at conjugate locations and on a regional scale have been explained in terms of seasonal influence on the background electron density coupled with the presence of large scale traveling ionospheric disturbances and low latitude associated processes the major highlight of this study is the simultaneous confirmation of most of the previously observed features and their underlying physical mechanisms during geomagnetic storms through a multi data set examination of hemispheric differences 2020 american geophysical union all rights reserved

ionospheric signatures of plasmaspheric tails 1 we make direct comparisons between gps maps of total electron content tec over the north american continent millstone hill radar observations of storm enhanced density and low and high altitude satellite measurements of the perturbation of the outer plasmasphere during the march 31 2001 geomagnetic storm we find that storm enhanced density sed and plumes of greatly elevated tec are associated with the erosion of the outer plasmasphere by strong sub auroral polarization electric fields the sed tec plumes identified at low altitude map closely onto the magnetospheric determination of the boundaries of the plasmapause and plasmaspheric tail determined by euv imaging from the image spacecraft characteristics of the sed tec plumes tails for the march 31 2001 event are tec 100 tecu f region sunward velocity 1000 m s sunward flux 5 1024 ions s 1 total transport to dayside magnetopause merging region 3 hr event 5 1028 ions

first tomographic image of ionospheric outflows 1 an image of the dayside low energy ion outflow event that occurred on 16 december 2003 was constructed with ground and space based gps global positioning system total electron content tec data and ion drift meter data from the dmsp defense meteorological satellite program a tomographic reconstruction technique has been applied to the gps tec data obtained from the gps receiver on the low earth orbit leo satellite fedsat the two dimensional tomographic image of the topside ionosphere and plasmasphere reveals a spectacular beam like dayside ion outflow emanating from the cusp region the transverse components of the magnetic field in fedsat s newmag data show the presence of field aligned current fac sheets indicating the existence of low energy electron precipitation in the cusp region the dmsp ion drift data show upward ion drift velocities and upward fluxes of low energy ions and electrons at the orbiting height of the dmsp spacecraft in the cusp region this study presents the first tomographic image of the flux tube structure of ionospheric ion outflows from 0 13 re up to 3 17 re altitude

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

the null hypothesis globally steady rates of erosion weathering fluxes and shelf sediment accumulation during late cenozoic mountain uplift and glaciation at the largest time and space scales the pace of erosion and chemical weathering is determined by tectonic uplift rates deviations from equilibrium arise from the transient response of landscape denudation to climatic and tectonic perturbations we posit that the constraint of mass balance however makes it unlikely that such disequilibrium persists at the global scale over millions of years as has been proposed for late cenozoic erosion we synthesize weathering fluxes global sedimentation rates sediment yields and tectonic motions to show a remarkable constancy in the pace of earth surface evolution over the last 10 ma and support the null hypothesis that global rates of landscape change have remained constant over this time period despite global climate change and mountain building events this work undermines the hypothesis that increased weathering due to mountain building or climate change was the primary agent for a decrease in global temperatures