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

a dynamical system model of eco geomorphic response to landslide disturbance vegetated landscapes form through the interactions of ecologic and geomorphic processes these interactions are generally slow and steady but they are occasionally the subject of abrupt disturbance in humid uplands for example landslides episodically disrupt forest growth and regolith development suddenly mobilize soil regolith and bedrock and facilitate runoff driven erosion by abruptly removing canopy protection over a wide area here we model such an environment as a stochastically perturbed dynamical system whose simplified low dimensionality makes its eco geomorphic interactions easier to explore and understand the model captures some of the spatial variability across a catchment by treating an ensemble of subcatchments in each aggregated biomass and regolith coevolve as a two dimensional dynamical system subject to episodic disturbance by slope failure this coevolution gives rise to a notional stable equilibrium between regolith and biomass but one that is not achieved in practice where landslide disturbance is significant instead a catchment scale ensemble average state arises in which higher storm frequency entails thinner regolith less biomass and weaker canopy protection against runoff erosion the model makes the counter intuitive prediction that as rainfall triggered landslides become more frequent their contribution to the erosion of weathered bedrock will diminish as the role from storm runoff erosion rises in some environments apparently dominated by landsliding the model predicts that runoff erosion may be more important in the removal of regolith and fine sediment from hillslopes than mass wasting

interhemispheric plasma flows in the equatorial topside ionosphere latitudinal longitudinal and seasonal variations in the field aligned and perpendicular flows measured at an altitude near 830 km by the defense meteorological satellite program f10 satellite are examined these profiles are studied during the nighttime 2100 magnetic local time for solstice periods in 1991 when the solar activity is high latitude and longitude variations show the influence of f region winds in modulating the observed field aligned flows at night large downward field aligned flows of the order 400 600 ms 1 are observed in the winter hemisphere and coincide in longitude with the location of previously identified adiabatic heating effects studied by venkatraman and heelis 1999a interhemispheric flows at 2100 hours local time are seen to extend up to apex heights of 1000 km during times of high solar activity perpendicular drifts however are relatively invariant with latitude as expected

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

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

hydrogeomorphic processes in a steep debris flow initiation zone 1 many debris flows initiate in steep channels 20 degrees yet studies have focused on lower gradient streams where failure is controlled by water height above channel deposits multiple debris flows in a steep channel in ohya landslide central japan were linked to infilling processes i e freeze thaw and dry ravel and partial saturation of accumulated sediment because of very active geomorphic processes in this catchment 39 debris flows were observed in the past 6 yr pre and post event imagery indicates selective transport of finer materials during most debris flows that comprise saturated and unsaturated flows however fluvial sediment processes important in relation to debris flow initiation in gentler channels were minimal critical conditions for the movement of such unsaturated materials are derived by equating shear stress with solid friction of the channel bed

nonlinear barotropic response to a localized topographic forcing formation of a tropical surf zone and its effect on interhemispheric propagation abstract the nonlinear response of a barotropic nondivergent spherical flow representative of the upper troposphere but without a tropical hadley cell to localized extratropical topographic forcing is examined using high resolution contour surgery calculations the response is shown to vary greatly with forcing amplitude and can be significantly different from the linear response at large amplitude rossby wave breaking occurs in the tropics irrespective of the direction of the equatorial winds and leads to small scale stirring and the formation of a tropical surf zone which inhibits the meridional propagation of the disturbance

supercooled ion temperatures observed in the topside ionosphere at dawn meridian during storm periods 1 a few rare events of supercooled ion temperature near the magnetic equator at dawn meridian have been observed by the first satellite of the republic of china rocsat 1 at 600 km altitude the ion cooling event occurs within a narrow longitude region where a large density reduction together with a large downward eastward and field aligned flow is observed although ion temperature troughs around the magnetic equator have been observed by many satellites before and the interhemispheric plasma transport of adiabatic cooling effect for ions near the equator has been modeled to explain the past observations the current observation enunciates some new facts of the ion cooling effect that have not been reported first ion cooling events are observed by rocsat at an unprecedented low altitude of 600 km during the solar maximum years of 2000 and 2001 second the ion temperature trough is observed together with a large density reduction and a large downward and eastward drift that were absent in the past observations third the present events are only observed near the dawn meridian during the disturbed periods comparing the observational facts with the existing models we conclude that the model of interhemispheric plasma transport bailey et al 1973 heelis et al 1978 bailey and heelis 1980 seems to fit best with the current observations however instead of resorting to the quiet time neutral wind to induce the quasi steady state plasma transport as modeled before a storm time transient dynamical process could have occurred within a limited longitude region where ions at high latitudes are forced to move along the field lines to the dip equator to cause ion cooling observed at 600 km lower than predicted in the model this storm time ionospheric process could be related to the creation of a westward electric field in the inner magnetosphere near the dawn meridian from a sudden enhancement of the convection field during a disturbed period modeled in the comprehensive ring current model fok et al 2003

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

specifying the equatorial ionosphere using cindi on c nofs cosmic and data interpolating empirical orthogonal functions 1 data interpolating empirical orthogonal functions dineofs are a data based method for determining a few orthogonal basis functions that optimally reproduce a given data set this technique is applied to meridional drift measurements performed by the coupled ion neutral dynamics investigation cindi onboard the communication navigation outage forecasting system c nofs as well as electron density profiles derived from gps radio occulations ro performed by the constellation observing system for meteorology ionosphere and climate cosmic the low densities of the equatorial ionosphere spanning 2009 2010 restricted quality drift measurements by cindi to altitudes near perigee limiting the local time coverage of measurements full local time descriptions may be obtained as perigee moves through all local times though this requires a minimum 67 day season to increase the data coverage of the ionosphere cindi data are supplemented with cosmic gps ro data dineofs are applied to median meridional drift measurements as well as cosmic measurements spanning 2009 2010 and are used to make a best estimate of the equatorial ionosphere at locations not observed the scattered distribution of cosmic profiles as well as the physical relationship between meridional ion drifts and the distribution of density with altitude improves the quality of the reconstructions compared to using cindi alone the dineof reconstructions demonstrate that the annual anomaly of reduced ionospheric densities in june compared to december measured by cosmic is coincident with a change in the meridional ion drifts at the geomagnetic equator measured by cindi

vegetation modulated landscape evolution effects of vegetation on landscape processes drainage density and topography 1 topography acts as a template for numerous landscape processes that include hydrologic ecologic and biologic phenomena these processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes we have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches vegetation is assumed to form a uniform ground cover runoff erosion is modeled based on a power function of excess shear stress in which shear stress efficiency is inversely proportional to vegetation cover this approach is validated using data plant effect on slope stability is represented by additional cohesion provided by plant roots vegetation cover is assumed to reduce sediment transport rates due to physical creep processes rainsplash dry ravel and expansion and contraction of sediments according to a negative exponential relationship vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances runoff erosion and landsliding and wildfires analytical results suggest that in an equilibrium basin with a fixed vegetation cover plants may cause a transition in the dominant erosion process at the channel head a runoff erosion dominated landscape under none or poor vegetation cover may become landslide dominated under a denser vegetation cover the sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena with model parameter values representative of the oregon coast range ocr numerical experiments conducted using the channel hillslope integrated landscape development child model confirm the findings based on the analytical theory a highly dissected fluvial landscape emerges when surface is assumed bare when vegetation cover is modeled landscape relief increases resulting in hollow erosion dominated by landsliding interestingly our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure simulated landscapes resemble real world catchments in the ocr when such disturbances are considered

equatorial longitude and local time variations of topside magnetic field aligned ion drifts at solar minimum 1 in the topside ionosphere the high mobility of the plasma along the magnetic field allows field aligned ion drifts to occur readily as a result of field aligned gravitational forces collisional forces or pressure gradients therefore variations in the field aligned ion drifts can be used to explore the influence of thermospheric electrodynamic and chemical processes on the ionosphere longitude and local time variations in the field aligned ion drifts near the magnetic equator are presented using observations from the coupled ion neutral dynamics investigation on board the communications navigation outage forecast system satellite these observations were obtained during the period of extremely low solar activity present in 2008 and 2009 allowing the seasonal local time and longitudinal variations to reveal the relative importance of the processes responsible for topside field aligned plasma drifts during solar minimum this investigation found that the low altitude winds and tides the net ionization or loss and the meridional e b drift were all influential in creating longitudinal and local time variations in the field aligned drift though the strength of the influence seen by each driver was found to vary with season local time and longitude

climatology of upward propagating diurnal and semidiurnal tides in the thermosphere 1 a major challenge in delineating and understanding the space weather of the ionosphere thermosphere system is the lack of global tidal observations in the 120 400 km thermospheric gap between satellite remote sensing and in situ tidal diagnostics this paper aims to close this gap by presenting an observation based climatological tidal model of the thermosphere ctmt of self consistent upward propagating migrating and nonmigrating diurnal and semidiurnal tides from 80 400 km and pole to pole for moderate f10 7 110 sfu solar flux conditions ctmt includes the 6 8 most important diurnal semidiurnal tidal components for temperature density and zonal meridional and vertical winds and is based on hough mode extension fits to 2002 2008 mean timed satellite tidal diagnostics in the mesosphere lower thermosphere mlt validation with independent 2002 2008 champ tidal diagnostics f10 7 105 sfu around 400 km proves that the approach captures nonmigrating tides well indicating that these waves propagate directly upward without significant tidal forcing occurring in the thermosphere notable exceptions are the dw2 and d0 components that are most likely generated in situ by nonlinear interaction forcing in the upper thermosphere ctmt is suitable for driving upper atmosphere models that require self consistent tidal fields in the mlt region as a lower boundary condition it does not include migrating tides due to in situ euv absorption in the upper thermosphere but allows us to quantitatively assess thermospheric variability due to tides from the lower atmosphere this is done by discussing longitude latitude maps of reconstructed diurnal and semidiurnal tidal variations as function of altitude and local time

the source of the longitudinal asymmetry in the ionospheric tidal structure 1 we examine the source of the longitudinal asymmetry in the ionospheric tidal structure by using the measurements of the plasma density and vertical plasma drift by the first republic of china satellite the consistent feature in plasma density and vertical plasma drift in all months is the development of the wave crests near 0 10 e and 90 100 e longitude the appearance of the global wave 4 or wave 3 structure is determined by the morphology between 150 e and 300 e longitude two crests are pronounced in july september and only one crest appears during the december solstice in that longitude region the crests of the wave 4 structure between 150 e and 300 e longitude are much weaker than the crests near the longitudes of 0 and 90 e during july september the wave 3 structure is pronounced in all months the phase difference between the wave 3 and wave 4 structures is small near the longitudes of 0 and 90 e and thus the superposition of the wave 3 structure amplifies the wave 4 crest intensity in those regions the phase difference is large between 150 e and 300 e longitude and thus the destructive superposition of the wave 3 component weakens the wave 4 crest in that region the wave 3 and wave 4 structures are the permanent ionospheric features and the significant portion of the longitudinal asymmetry is explained by the phase difference of the two structures

riverine particulate organic carbon from an active mountain belt importance of landslides 1 we investigate the routing and transfer of particulate organic carbon poc from the western southern alps new zealand using organic carbon corg and nitrogen norg concentrations and stable carbon isotopes 13corg in this active mountain belt sediment discharge is dominated by landslide derived material landsliding acts to homogenize the geochemically diverse hillslope poc mixing poc from the standing biomass and soil with the fossil poc from bedrock as a result the poc in river sediment at the mountain front is a binary mixture of fossil and nonfossil carbon sourced from many landslide deposits we calculate that nonfossil biogenic poc makes up 63 7 of the total poc in the suspended load of rivers draining the western southern alps the erosional flux of biogenic poc from these catchments represents a transfer of 39 tc km 2 a 1 of atmospheric co2 averaged over the west flank of the mountain belt if more than 10 of this poc is preserved in sediments on geological timescales then this process is the most significant way in which the southern alps and similar tectonically active mountain belts with restricted alluvial aprons consume atmospheric co2

ion temperature crests and troughs in the morning sector of the low latitude and midlatitude topside ionosphere 1 the low latitude and midlatitude topside ionospheric ion temperature at 600 km altitude has been measured with the ionospheric plasma and electrodynamics instrument ipei instrument on board rocsat 1 satellite in the solar maximum year of 2000 global hemispheric asymmetrical distribution of this topside ion temperature in the morning hour is presented here for the first time and is explained with the associated observation of the field aligned ion flow and ion concentration crests of ion temperature are found along the dip latitudes between 10 and 25 in the winter hemisphere during the solstice seasons the maximum in the temperature crests is located in a longitudinal region of positive magnetic declination in the southern hemisphere during the june solstice and in the longitudinal region of negative magnetic declination in the northern hemisphere during the december solstice ion compression from a downward field aligned ion flow driven by morning neutral wind is concluded to cause the ion heating in the winter hemisphere as modeled by bailey et al 1975 on the other hand in the 0700 0800 lt sector there are low temperature regions at higher latitudes in a longitude region of negative magnetic declination in the southern hemisphere during the june solstice and in the longitudinal region of positive magnetic declination in the northern hemisphere during the december solstice a low photoionization rate together with an ion expansion cooling process from the upward field aligned plasma flow has resulted in such low temperature in these regions as for temperature troughs observed near the dip equator in the morning hour it is attributed to the convective heat loss in the summer hemisphere initially in the early morning hour and then to the rapid increase of plasma concentration at the dip equator in the late morning hour for all seasons

landslides earthquakes and erosion this paper relates landslide inventories to erosion rates and provides quantitative estimates of the landslide hazard associated with earthquakes we do this by utilizing a three parameter inverse gamma distribution which fits the frequency area statistics of three substantially dcompletet landslide event inventories a consequence of this general distribution is that a landslide event magnitude ml lognlt can be introduced where nlt is the total number of landslides associated with the landslide event using this general distribution landslide event magnitudes ml can be obtained from incomplete landslide inventories and the total area and volume of associated landslides as well as the area and volume of the maximum landslides can be directly related to the landslide event magnitude using estimated recurrence intervals for three landslide events and the time span for two historical inventories we estimate regional erosion rates associated with landslides as typically 0 1 2 5 mm year 1 we next give an empirical correlation between the earthquake magnitude associated landslideevent magnitude and the total volume of associated landslides using these correlations we estimate that the minimum earthquake magnitudes that will generate landslides is m 4 3f0 4 finally using gutenberg richter frequency magnitude statistics for regional seismicity we relate the intensity of seismicity in an area and the magnitude of the largest regional earthquakes to erosion rates we find that typical seismically induced erosion rates in active subduction zones are 0 2 7 mm year 1 and adjacent to plate boundary strike slip fault zones are 0 01 0 7 mm year 1

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

landslide rupture and the probability distribution of mobilized debris volumes 1 landslide driven erosion is controlled by the scale and frequency of slope failures and by the consequent fluxes of debris off the hillslopes in this paper we tackle the magnitude frequency part of the process and develop a theory of initial slope failure and debris mobilization that reproduces the heavy tailed distributions probability density function or pdfs observed for landslide source areas and volumes landslide rupture propagation is treated as a quasi static noninertial process of simplified elastoplastic deformation with strain weakening debris runout is not considered the model tracks the stochastically evolving imbalance of frictional cohesive and body forces across a failing slope and uses safety factor concepts to convert the evolving imbalance into a series of incremental rupture growth or arrest probabilities a single rupture is simulated with a sequence of weighted coin tosses with weights set by the growth probabilities slope failure treated in this stochastic way is a survival process that generates asymptotically power law tail pdfs of area and volume for rock and debris slides predicted scaling exponents are consistent with analyses of landslide inventories the primary control on the shape of the model pdfs is the relative importance of cohesion over friction in setting slope stability the scaling of smaller shallower failures and the size of the most common landslide volumes are the result of the low cohesion of soil and regolith whereas the negative power law tail scaling for larger failures is tied to the greater cohesion of bedrock

observations of dc electric fields in the low latitude ionosphere and their variations with local time longitude and plasma density during extreme solar minimum 1 dc electric fields and associated e b plasma drifts detected with the double probe experiment on the c nofs satellite during extreme solar minimum conditions near the june 2008 solstice are shown to be highly variable with weak to moderate ambient amplitudes of 1 2 mv m 25 50 m s average field or drift patterns show similarities to those reported for more active solar conditions i e eastward and outward during day and westward and inward at night however these patterns vary significantly with longitude and are not always present daytime vertical drifts near the magnetic equator are largest in the prenoon sector observations of weak to nonexistent prereversal enhancements in the vertical drifts near sunset are attributable to reduced dynamo activity during solar minimum as well as seasonal effects enhanced meridional drifts are observed near sunrise in certain longitude regions precisely where the enhanced eastward flow that persisted from earlier local times terminates the nightside ionosphere is characterized by larger amplitude structured electric fields dominated by horizontal scales of 500 1500 km even where local plasma densities appear relatively undisturbed data acquired during successive orbits indicate that plasma drifts and densities are persistently organized by longitude the high duty cycle of the c nofs observations and its unique orbit promise to expose new physics of the low latitude ionosphere

on the variation in the ionospheric response to geomagnetic storms with time of onset recent observations from immel and mannucci 2013 have indicated that geomagnetic storms cause larger enhancements in the ionospheric plasma density and total electron content tec in the american sector than anywhere else on the planet this suggests that the presence of a ut storm onset effect is important for correctly understanding the impact longitudinal structure and timing of geomagnetic storms using the global ionosphere thermosphere model gitm we conduct a modeling experiment of the august 2011 geomagnetic storm by modifying the storm arrival time ut in earth s daily rotation and examining the subsequent system response we find that the simulations reflect the recent studies indicating that the strongest enhancements of tec are in the american and pacific longitude sectors of storms with onsets between 1600 ut and 2400 ut the underlying mechanisms of the strong tec increases during storm times in these longitude sectors are also examined some of the resulting tec structures may be explained by changes in the o n2 ratio especially in the high latitudes but it is unable to explain all of the variability in the equatorial regions storm time neutral winds and vertical ion motions coupled to earth s asymmetrical geomagnetic topology appear to be driving the longitude sector variability due to ut storm onset times

the isotopic composition of particulate organic carbon in mountain rivers of taiwan small rivers draining mountain islands are important in the transfer of terrestrial particulate organic carbon poc to the oceans this input has implications for the geochemical stratigraphic record we have investigated the stable isotopic composition of poc 13corg in rivers draining the mountains of taiwan in 15 rivers the suspended load has a mean 13corg that ranges from 28 1 0 8 to 22 0 0 2 on average 37 samples per river over the interval of our study to investigate this variability we have supplemented suspended load data with measurements of poc in bedrock and river bed materials and constraints on the composition of the terrestrial biomass fossil poc in bedrock has a range in 13corg from 25 4 1 5 to 19 7 2 3 between the major geological formations using coupled 13corg and n c we have found evidence in the suspended load for mixing of fossil poc with non fossil poc from the biosphere in two rivers outside the taiwan central range anthropogenic land use appears to influence 13corg resulting in more variable and lower values than elsewhere in all other catchments we have found that 5 variability in 13corg is not controlled by the variable composition of the biomass but instead by heterogeneous fossil poc in order to quantify the fraction of suspended load poc derived from non fossil sources fnf as well as the isotopic composition of fossil poc 13cfossil carried by rivers we adapt an end member mixing model river suspended sediments and bed sediments indicate that mixing of fossil poc results in a negative trend between n c and 13corg that is distinct from the addition of non fossil poc collapsing multiple fossil poc end members onto a single mixing trend as an independent test of the model fnf reproduces the fraction modern fmod in our samples determined from 14c measurements to within 0 09 at the 95 confidence level over the sampling period the mean fnf of suspended load poc was low 0 29 0 02 n 459 in agreement with observations from other mountain rivers where physical erosion rates are high and fossil poc enters river channels the mean 13cfossil in suspended poc varied between 25 2 0 5 and 20 2 0 6 from catchment to catchment this variability is primarily controlled by the distribution of the major geological formations it also covers entirely the range of 13corg found in marine sediments which is commonly thought to derive from mixing between marine and terrigenous poc if land sourced poc is preserved in marine sediments then changes in the bulk 13corg observed offshore taiwan could instead be explained by changes in the onshore provenance of sediment the range in 13corg of fossil organic matter in sedimentary rocks exposed at the surface is large and given the importance of these rocks as a source of clastic sediment to the oceans care should be taken in accounting for fossil poc in marine deposits supplied by active mountain belts

the 10th generation international geomagnetic reference field abstract the international association of geomagnetism and aeronomy iaga on 12 december 2004 released the 10th generation international geomagnetic reference field igrf the latest version of a standard mathematical description of the earth s main magnetic field and used widely in studies of the earth s deep interior its crust ionosphere and magnetosphere the coefficients were finalised by a task force of iaga the igrf is the product of a large collaborative effort between magnetic field modellers and the institutes involved in collecting and disseminating magnetic field data from satellites and observatories around the world

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

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

meridional winds derived from cosmic radio occultation measurements 1 meridional winds at the magnetic meridian in the upper thermosphere are derived from the peak height and density of the ionospheric f2 layer as retrieved by the constellation observing system for meteorology ionosphere and climate cosmic satellites for 4 months from november 2006 to february 2007 these winds referred to as cosmic winds are first validated by comparison at multiple locations with winds obtained from ground based incoherent scatter radar isr and fabry perot interferometer fpi measurements then longitudinal variations of these winds are investigated and compared with simulations by the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model ncar tie gcm the results show generally good agreement between cosmic winds ground based measurements and the simulations significant longitudinal variations are presented in the cosmic winds at 40 n local winter around midnight the cosmic winds exhibit stronger and longer duration equatorward velocities within 110 w 20 w large negative magnetic declination sector than those in other longitudes during late morning hours the poleward winds show similar longitudinal variations at 40 s local summer during the daytime the poleward winds are stronger within 120 e 110 w large positive magnetic declination sector than in 60 w 90 e large negative magnetic declination sector while during the nighttime the maximum equatorward winds shifts about 2 h later in 60 w 90 e than in 120 e 110 w analysis of the tie gcm simulations suggests that the longitudinal variation of meridional winds is mainly induced by magnetic declination due to the contribution of geographic zonal wind