characterization and quantification of aquifer heterogeneity using outcrop analogs at the canadian forces base borden ontario canada accurate characterization of internal structures and geometries of aquifers is critical for evaluation of plume migration and dispersion of contaminants for this reason high resolution transport study field sites such as the waterloo groundwater research site at the canadian forces base borden ontario canada have been established however geological characterization at this site is based primarily on cores and shallow geophysical data outcrop analog studies offer detailed horizontal data that can help to build quantified models of aquifer heterogeneity we used a combination of ground based light detection and ranging lidar and high resolution photographs at a sand quarry cut into borden aquifer sediment to evaluate and quantify the distribution of lithofacies and hydrofacies that control flow properties in the borden aquifer we exposed sixteen 20 m 1 5 m outcrops lidar surveyed photographed and field mapped lithofacies at each exposure and segmented the lithofacies from photographs to produce maps of facies distributions we grouped different lithofacies into hydrofacies based on overall facies geometry and estimated hydraulic properties we used lidar scans and the segmented facies maps to produce a digital outcrop model dom of the site the resultant dom combines lithofacies and hydrofacies derived from field observations with high resolution 5 mm lidar data to reconstruct hydrofacies distributions in a three dimensional 3 d geomodel the dom offers a relatively complete horizontal correlation structure that was used in transition probability geostatistical modeling to create realizations of hydrofacies distributions in the aquifer at the study site

high resolution altimetry reveals new characteristics of the december 2004 indian ocean tsunami 1 the indian ocean tsunami which occurred on december 26 2004 was the first to be clearly observed using satellite altimeters the wave amplitude observed in deep ocean by topex and jason 1 was close to 60 cm about 2 hours after the earthquake envisat crossed the tsunami wave 3h15 after the earthquake and measured a 35 cm wave even though it flew over the tsunami 7h20 after the earthquake gfo still observed a wave close to 20 cm to better extract the tsunami signal from altimeter measurements a specific ocean variability mapping technique is used this technique proves to be mandatory for discriminating tsunami waves from other ocean signals altimeter signals are then compared with those derived from the cea commissariat a l energie atomique model outputs for the first time with altimeter data peculiar short wavelengths signals along jason 1 and envisat profiles have been detected from the analysis of 20 hz altimeter measurements such high wavenumber signals can be explained by the dispersive propagation of tsunami waves these observations highlight the essential role of satellite altimeter measurements to better understand and to improve models of tsunami wave propagation and dissipation

reconstruction of ionospheric perturbation induced by 2004 sumatra tsunami using a computerized tomography technique a computerized tomography technique is used to reconstruct a 3 d profile of electron density perturbation in the ionosphere based on the total electron content data recorded at a planned gps receiver network simulations are conducted using the data of the 2004 sumatra event an effective early warning system may become feasible based on this work

identification of inclined ionospheric layers using analysis of gps occultation data the ionosphere and atmosphere may have significant impacts on the high stable navigational signals of the global positioning system gps in the communication link satellite to satellite the classification of the different types of the ionospheric impact on the phase and amplitude of the gps signals at altitudes of 40 90 km is introduced using the challenging minisatellite payload champ radio occultation ro data an analytical model is elaborated for the description of the radio wave propagation in the stratified ionosphere and atmosphere the propagation medium consists of sectors having the spherically symmetric distributions of refractivity the newly developed model presents analytical expressions for the phase path and refractive attenuation of radio waves the model explains significant amplitude and phase variations at altitudes of 40 90 km of the ro ray perigee associated with the influence of the inclined ionospheric layers an innovative eikonal acceleration technique is described and applied to the identification and location of the inclined ionospheric layers using the comparative analysis of the amplitude and phase variations of the ro signals

hydrophobic organic contaminant transport property heterogeneity in the borden aquifer we determined that the spatial heterogeneity in aquifer properties governing the reactive transport of volatile organic contaminants is defined by the arrangement of lithofacies we measured permeability k and perchloroethene sorption distribution coefficient kd for lithofacies that we delineated for samples from the canadian forces base borden aquifer we compiled existing data and collected 57 new cores to characterize a 30 m section of the aquifer near the test location of mackay et al 1986 the k and kd were measured for samples taken at six elevations from all cores to create a data set consisting of nearly 400 colocated measurements through analysis of variance corrected for multiple comparisons we determined that the 12 originally mapped lithofacies could be grouped into five relatively distinct chemohydrofacies that capture the variability of both transport properties the mean of ln k by lithofacies was related to the grain size and the variance was relatively consistent in contrast both the mean and variance of ln kd were greater for more poorly sorted lithofacies which were also typically more coarse grained half of the aquifer sorption capacity occurred in the three highest sorbing lithofacies but comprised only 20 of its volume the model of the aquifer that emerged is that of discontinuous scour fill deposits of medium sand generally characterized by greater kd and k within laterally extensive fine grained to very fine grained sands of lower kd and k our findings demonstrate the importance of considering source rock composition transport and deposition processes when constructing conceptual models of chemohydrofacies

comparisons of ionospheric electron density distributions reconstructed by gps computerized tomography backscatter ionograms and vertical ionograms global positioning system gps computerized ionosphere tomography cit and ionospheric sky wave ground backscatter radar are both capable of measuring the large scale two dimensional 2 d distributions of ionospheric electron density ied here we report the spatial and temporal electron density results obtained by gps cit and backscatter ionogram bsi inversion for three individual experiments both the gps cit and bsi inversion techniques demonstrate the capability and the consistency of reconstructing large scale ied distributions to validate the results electron density profiles obtained from gps cit and bsi inversion are quantitatively compared to the vertical ionosonde data which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings our study can improve current understanding of the capability and insufficiency of these two methods on the large scale ied reconstruction

critical crater diameter and asteroid impact seismology if impact stress reverberation is the primary gradational process on an asteroid at global scales then the largest undegraded crater records an asteroid s seismological response the critical crater diameter dcrit is defined as the smallest crater whose formation disrupts all previous craters globally up to its size it is solved for by combining relationships for crater growth and for stress attenuation the computation for dcrit gives a simple explanation for the curious observation that small asteroids have only modest undegraded craters in comparison to their size whereas large asteroids have giant undegraded craters dcrit can even exceed the asteroid diameter in which case all craters are local and the asteroid becomes crowded with giant craters dcrit is the most recent crater to have formed on a blank slate when it is equated to the measured diameter of the largest undegraded crater on known asteroids peak particle velocities are found to attenuate with the 1 2 1 3 power of distance less attenuative than strong shocks and more characteristic of powerful seismic disturbances this is to be expected since global degradation can result from seismic cm s 1 particle velocities on small asteroids attenuation as modeled appears to be higher on asteroids known to be porous although these are also bodies for which different crater scaling rules might apply

radar observations and the shape of near earth asteroid 2008 ev5 abstract we observed the near earth asteroid 2008 ev5 with the arecibo and goldstone planetary radars and the very long baseline array during december 2008 ev5 rotates retrograde and its overall shape is a 400 50 m oblate spheroid the most prominent surface feature is a ridge parallel to the asteroid s equator that is broken by a concavity about 150 m in diameter otherwise the asteroid s surface is notably smooth on decameter scales ev5 s radar and optical albedos are consistent with either rocky or stony iron composition the equatorial ridge is similar to structure seen on the rubble pile near earth asteroid 66391 1999 kw4 and is consistent with yorp spin up reconfiguring the asteroid in the past we interpret the concavity as an impact crater shaking during the impact and later regolith redistribution may have erased smaller features explaining the general lack of decameter scale surface structure

radar constraints on asteroid regolith properties using 433 eros as ground truth abstract radar data enable us to estimate an asteroid s near surface bulk density thus providing a joint constraint on near surface porosity and solid density we investigate two different approaches to simplifying this joint constraint estimating solid densities by assuming uniform porosities for all asteroids and estimating porosities by assuming uniform mineralogy within each taxonomic class methods used to estimate asteroids near surface solid densities from radar data have not previously been calibrated via independent estimates recent spacecraft results on the chondritic nature of 433 eros now permit such a check and also support porosity estimation for s class objects we use radar albedos and polarization ratios estimated for 36 main belt asteroids and nine near earth asteroids to estimate near surface solid densities using two methods one of which is similar to the uncalibrated algorithms used in previous studies the other of which treats eros as a calibrator we also derive porosities for the same sample by assigning solid densities for each taxonomic class in advance density estimation results obtained for eros itself are consistent with the uncalibrated method being valid in the mean those derived for the full sample imply that uncalibrated solid densities are at most a few tens of percent too large on average however some derived densities are extremely low whereas most porosity estimates are physically plausible we discuss the relative merits of these two approaches

ionospheric remote sensing of the denali earthquake rayleigh surface waves 1 using the global positioning system we have detected ionospheric disturbances associated with the long period rayleigh waves from the 2002 denali earthquake ms 7 9 the dense california gps networks allowed us to map the ionospheric perturbations and to compute the group velocity with a high spatial resolution above the pacific coasts due to a low sampling rate a large error in the velocity determination remains nonetheless it demonstrates that bi static remote sensing measurements of seismic waves with gps networks can be performed monostatic measurements with a dedicated satellite could possibly be used to record in the ionosphere surface waves originating from large earthquakes such a space based remote sensing of the local group velocity of rayleigh surface waves would effectively complement the seismic networks for high resolution global tomography of the earth s lithosphere

ionospheric gps total electron content tec disturbances triggered by the 26 december 2004 indian ocean tsunami 1 tsunami ionospheric disturbances tids of the 26 december 2004 mw 9 3 sumatra earthquake are detected by the total electron content tec of ground based receivers of the global positioning system gps in the indian ocean area it is found that the tsunami waves triggered atmospheric disturbances near the sea surface which then traveled upward with an average velocity of about 730 m s 2700 km hr into the ionosphere and significantly disturbed the electron density within it results further show that the tids which have maximum height of about 8 6 17 2 km periods of 10 20 min and horizontal wavelengths of 120 240 km travel away from the epicenter with an average horizontal speed of about 700 km hr 190 m s in the ionosphere

combined ionospheric campaign 1 ionospheric tomography and gps total electron count tec depletions results from the june 1998 combined ionospheric campaign cic are presented the cic represents an attempt to focus a large number of different instruments on one interesting geophysical region the center for ionospheric research cir at applied research laboratories the university of texas at austin arl ut has had several computerized ionospheric tomography cit receivers deployed in the caribbean region since july 1997 in this paper we compare cit data gps tec data and data from the incoherent scatter radar at arecibo to try to obtain an understanding of the temporal and spatial distribution of ionospheric structure observed during the campaign we use the three data sets as inputs to the 3dvar tomography algorithm developed at cir and present results of the 3dvar objectively analyzed electron density field an ionization wall was found near 40 latitude in agreement with previous millstone hill and dmsp observations in high kp several elongated density depletions were also detected

the small inner satellites of saturn shapes structures and some implications abstract properties of the small inner satellites of saturn are updated using final cassini image data the equatorial ridges on pan and atlas are morphologically structurally and gravitationally distinct from their cores and represent distinct additions to rather than modifications of the precursor bodies exposures of lineated substrates on pandora and epimetheus show a relationship between regolith grooves and structures in underlying bedrock structures exposed on epimetheus suggest formation at depth including filling or annealing of fractures these structures and sharp bedrock regolith boundaries indicate a history far more complex than simple rubble pile assembly these exposures of bedrock also indicate past removal of the expected regolith from large fractions of these object s surfaces late in their cratering records

asteroid 2867 steins shape topography and global physical properties from osiris observations the rosetta spacecraft flew by asteroid 2867 steins on 5 september 2008 allowing the onboard osiris cameras to collect the first images of an e type asteroid we implemented several three dimensional reconstruction techniques to retrieve its shape limb profiles combined with stereo control points were used to reconstruct an approximate shape model this model was refined using a stereophotoclinometry technique to accurately retrieve the topography of the hemisphere observed by osiris the unseen part of the surface was constrained by the technique of light curves inversion the global shape resembles a top with dimensions along the principal axes of inertia of 6 83 x 5 70 x 4 42 km it is conspicuously more regular than other small asteroids like 233 eros and 25143 itokawa its mean radius is r m 2 70 km and its equivalent radius radius of a sphere of equivalent volume is r v 2 63 km the north pole is oriented at ra 99 5 degrees and dec 59 5 degrees which implies a very large obliquity of 172 degrees and a retrograde rotation maps of the gravitational field and slopes were calculated for the well imaged part of the asteroid together with the shape they helped characterizing the most prominent topographic features identified at the surface of 2867 steins an equatorial ridge restricted to the extremities of the long axis a large crater having dimensions of 2100 x 1800 m in the southern hemisphere and an elongated hill in the northern hemisphere we conjecture that the equatorial ridge was formed by centrifugal acceleration as the asteroid was spun up by the yarkovsky o keefe radzievskii paddack effect c 2012 elsevier inc all rights reserved

numerical modeling of the great 2004 indian ocean tsunami focus on the mascarene islands on 26 december 2004 the m w 9 2 sumatra earthquake triggered the greatest tsunami ever observed in recent times the unprecedented quality and variety of observations on modern instruments provide opportunities to refine modeling techniques as well as our perception of tsunami hazard in oceanic regions where historical events are not as frequent as in the pacific ocean we present a numerical modeling of the 2004 tsunami on the mascarene islands with refined computations on la reunion island where postevent survey observations and one tide gauge record are available we use two different source models models a and b to account for the observations and we also test an additional source model model c to study the effect of a tsunami originating in the 1833 epicentral area southern sumatra a wave trapped on the edge of la reunion may explain the greatest water heights reached in the western coastline of the island the observed tide gauge data are reasonably well fit models a and b the run up data can also be explained with our models late disturbances observed in la pointe des galets may be explained by a late tsunami reflection from madagascar or by harbor resonances finally we also show that model c 1833 like strikes la reunion more heavily than models a and b

hayabusa2 arrives at the carbonaceous asteroid 162173 ryugu a spinning top shaped rubble pile the hayabusa2 spacecraft arrived at the near earth carbonaceous asteroid 162173 ryugu in 2018 we present hayabusa2 observations of ryugu s shape mass and geomorphology ryugu has an oblate spinning top shape with a prominent circular equatorial ridge its bulk density 1 19 0 02 grams per cubic centimeter indicates a high porosity 50 interior large surface boulders suggest a rubble pile structure surface slope analysis shows ryugu s shape may have been produced from having once spun at twice the current rate coupled with the observed global material homogeneity this suggests that ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation from these remote sensing investigations we identified a suitable sample collection site on the equatorial ridge

characterizing the heterogeneity and correlation of perchloroethene sorption and hydraulic conductivity using a facies based approach a facies based approach was used to delineate both geochemical and physical aquifer property heterogeneity specifically the parameters considered were the sorption coefficient kd for a model organic contaminant and hydraulic conductivity k inferred from the particle size distribution subfacies sized samples were analyzed for both tetrachloroethene kd and k in a vertical core of the borden aquifer both parameters were correlated with the six sedimentary facies identified within the vertical core as a consequence of their relations to sedimentary facies significant positive correlations between ln k and ln kd which were different from the core scale correlation and different from each other were identified for some facies fades specific correlations generally resulted in improved statistics i e higher correlation coefficients and reduced confidence intervals compared to the core scale correlation the results suggest that a facies based approach can be useful in characterizing the heterogeneity of the transport properties of sedimentary aquifers

near earth asteroid surface roughness depends on compositional class radar observations of 214 near earth asteroids neas reveal a very strong correlation of circular polarization ratio with visible infrared taxonomic class establishing distinct differences in the centimeter to several decimeter structural complexity of objects in different spectral classes the correlation may be due to the intrinsic mechanical properties of different mineralogical assemblages but also may reflect very different formation ages and collisional histories the highest ratios are measured for groups associated with achondritic igneous rocky meteorites the e class whose parent body may be 3103 eger and the v class derived from the mainbelt asteroid and dawn mission target 4 vesta

contaminant tailing in highly heterogeneous porous formations sensitivity on model selection and material properties summary coupled impacts of slow advection diffusion and sorption were investigated using two heterogeneity models that differ in structure and in the mathematical framework that was used to simulate flow and transport and to quantify contaminant tailing both models were built using data from a highly heterogeneous exposure of the borden aquifer at a site located 2 km north west of the stanford waterloo experimental site at canadian forces base borden ontario canada the inclusions based model used a simplified representation of the different materials found at the site while the second model was based on transitional probability geostatistics of the formation these two models were used to investigate sensitivity of contaminant tailing on model selection and on geometric and material properties while simulations were based on data collected at borden models were exercised beyond the geometric and material properties that characterize the site various realizations have identified very low conductive silty clay found at volume fraction of 23 4 as the material with dominant influence on tailing and vertical diffusion in and out of low conductive units affected by sorption as the dominant transport mechanism causing tailing the two models yielded almost identical transport results when vertical correlation lengths of silty clay were matched several practical implications relevant for characterization of low conductive units were identified and briefly discussed

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

imaging of small scale features on 433 eros from near evidence for a complex regolith on 25 october 2000 the near earth asteroid rendevous near shoemaker spacecraft executed a low altitude flyover of asteroid 433 eros making it possible to image the surface at a resolution of about 1 meter per pixel the images reveal an evolved surface distinguished by an abundance of ejecta blocks a dearth of small craters and smooth material infilling some topographic lows the subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter sized blocks

spatial distributions of perchloroethylene reactive transport parameters in the borden aquifer 1 we determined the descriptive statistical and spatial geostatistical properties of the perchloroethene ln kd and the ln k of a 1 5 m thick by 10 m horizontal transect of the borden aquifer near the location of the stanford waterloo sw tracer experiment the ln kd distribution is not normal and is right skewed because of a few high values that occur localized in two regions of the transect in contrast the ln k data can be characterized by a normal distribution a linear regression of ln kd on ln k yields a statistically significant positive correlation also shown at small lags in the cross correlogram no significant vertical or horizontal trend in the ln kd data was detected the semivariogram ranges of ln k and ln kd differ from one another in the vertical direction 0 33 0 06 m and 0 20 0 04 m respectively and are much less than the horizontal ranges a few meters despite significant effort the horizontal range of ln kd remains poorly characterized because of limitations of the sample locations many of the characteristics described above do not match those assumed in prior theoretical studies that examined the importance of various aquifer characteristics on sw tracer transport we suggest that there is knowledge to be gained by revisiting the conclusions of these prior studies in light of the new information presented here

a travel time based approach to model kinetic sorption in highly heterogeneous porous media via reactive hydrofacies we present a semi analytical model for the transport of solutes being subject to sorption in porous aquifers we couple a travel time based model of advective transport with a spherical diffusion model of kinetic sorption in non uniform material mixtures the model is formulated in the laplace domain and transformed to the time domain by numerical inversion by this three dimensional transport of solutes undergoing mass transfer between aqueous and solid phases can be simulated very efficiently the model addresses both hydraulic and reactive heterogeneity of porous aquifers by means of hydrofacies which function as homogeneous but non uniform subunits the total exposure time to each of these subunits controls the magnitude of sorption effects whereas the particular sequence of facies through which the solute passes is irrelevant we apply the model to simulate the transport of phenanthrene in a fluvio glacial aquifer for which the hydrofacies distribution is known at high resolution the lithological composition of each facies has been analyzed and sorption properties of the lithological components are available taking the fully resolved hydrofacies model as reference we evaluate different approximations referring to lower information levels reflecting shortcomings in typical modeling projects the most important feature for a good description of both the main breakthrough and tailing of phenanthrene is the non uniformity of the porous medium while spatial heterogeneity of chemical properties might be neglected without introducing a large error an approximation of the facies composition in terms of a uniform substitute material considerably compromises the quality of the modeling result this article is protected by copyright all rights reserved

two shell ionospheric model for indian region a novel approach in the u s wide area augmentation system european geostationary navigation overlay service and indian global positioning system aided geo augmented navigation a near real time grid based single shell model is proposed to correct the ionospheric delay at the user aircrafts the single shell model is based on the assumption that the whole ionosphere is compressed at a fixed altitude at 350 km this assumption may not be appropriate for the indian region which falls in the equatorial ionospheric anomaly belt in this paper a two shell model which incorporates two different shells at 300 and 500 km altitudes having different weights at different time domains has been implemented a statistical comparison between single and two shell models has been done for all quiet days of year 2005 based on the results it is observed that there is at least 60 improvement in the performance of the two shell model in comparison to the single shell model for the indian region

ionospheric response to the geomagnetic storm on august 21 2003 over china using gnss based tomographic technique the impacts of the august 21 2003 geomagnetic storm on the ionosphere over china have been first investigated by using the so called computerized ionospheric tomography cit technique and the observations of the crustal movement observation network of china tomographic results show that the main ionospheric effects of this geomagnetic storm over china are as follows 1 the negative storm phase effect appears in the f region and 2 the positive storm phase effect occurs above the f region meanwhile some key features in the ionospheric structure have been revealed in the ionospheric images during the storm this includes the disturbances and an elongated region of the reduced electron density at the latitude around 32 n statistical comparisons are carried out to confirm the reliability of the global navigation satellite system based cit reconstruction results using the profile obtained from ionosonde observations

plume persistence due to aquitard back diffusion following dense nonaqueous phase liquid source removal or isolation 1 at an industrial site on a sand aquifer overlying a clayey silt aquitard in connecticut a zone of trichloroethylene dense nonaqueous phase liquid dnapl at the aquifer bottom was isolated in late 1994 by installation of a steel sheet piling enclosure in response to this dnapl isolation three aquifer monitoring wells located approximately 330 m downgradient exhibited strong tce declines over the next 2 3 years from trichloroethylene tce concentrations between 5000 and 30 000 g l to values leveling off between 200 and 2000 g l tce concentrations from analysis of vertical cores from the aquitard below the plume and also from depth discrete multilevel systems in the aquifer sampled in 2000 were represented in a numerical model this shows that vertical back diffusion from the aquitard combined with horizontal advection and vertical transverse dispersion account for the tce distribution in the aquifer and that the aquifer tce will remain much above the mcl for centuries

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

three dimensional waveform modeling of ionospheric signature induced by the 2004 sumatra tsunami 1 the sumatra december 26th 2004 tsunami produced internal gravity waves in the neutral atmosphere and large disturbances in the overlying ionospheric plasma to corroborate the tsunamigenic hypothesis of these perturbations we reproduce with a 3d numerical modeling of the ocean atmosphere ionosphere coupling the tsunami signature in the total electron content tec data measured by the jason 1 and topex poseidon satellite altimeters the agreement between the observed and synthetic tec shows that ionospheric remote sensing can provide new tools for offshore tsunami detection and monitoring

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

the inner small satellites of saturn a variety of worlds more than a dozen small 150 km mean radius satellites occupy distinct dynamical positions extending from within saturn s classical rings to the orbit of dione the cassini mission has gradually accumulated image and spectral coverage of these objects to the point where some generalizations on surface morphology may be made objects in different dynamical niches have different surface morphologies satellites within the main rings display equatorial ridges the f ring shepherding satellites show structural forms and heavily cratered surfaces the co orbitals janus and epimetheus are the most lunar like of the small satellites satellites occupying libration zones trojan satellites have deep covering of debris subject to downslope transport small satellites embedded in ring arcs are distinctively smooth ellipsoids that are unique among small well observed solar system bodies and are probably relaxed effectively fluid equilibrium shapes indicative of mean densities of about 300 kg m 3

the rubble pile asteroid itokawa as observed by hayabusa during the interval from september through early december 2005 the hayabusa spacecraft was in close proximity to near earth asteroid 25143 itokawa and a variety of data were taken on its shape mass and surface topography as well as its mineralogic and elemental abundances the asteroid9s orthogonal axes are 535 294 and 209 meters the mass is 3 51 1010 kilograms and the estimated bulk density is 1 9 0 13 grams per cubic centimeter the correspondence between the smooth areas on the surface muses sea and sagamihara and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting itokawa is considered to be a rubble pile body because of its low bulk density high porosity boulder rich appearance and shape the existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re agglomeration into a rubble pile object

observations of the f region height redistribution in the storm time ionosphere over europe and the usa using gps imaging 1 ionospheric imaging with gps provides a near global view of the three dimensional time evolving ionosphere this is of particular interest during storms the focus of this paper is on the height redistribution of the plasma and in particular the longitudinal and latitudinal variations in the time of plasma uplifts three storms 15 july 2000 30 october 2003 and 20 november 2003 are studied here dramatic elevation of the f layer by more than one hundred kilometers was seen in the images during daytime over europe and the usa for all three storms all three showed an east west time delay of around one hour in the peak height elevation over some 85 longitude the 20 november 2003 storm also showed a north south time delay in the change in the f region height with the uplift seen first at high latitudes and then low latitudes independent evidence from other instruments and techniques are provided as supporting evidence that the peak height uplifts occurred candidate mechanisms of the peak height changes are electric fields and neutral winds and the roles of these drivers will be investigated in future modelling studies

global observation of the ionospheric electronic response to solar events using ground and leo gps data we present in this work the temporal evolution of the three dimensional electron density at global scale during two ionospheric storms october 18 19 1995 and january 10 1997 computed using only actual global positioning system data the tomographic model is solved by means of a kaiman filtering with a filter updating time of 1 hour in a sun fixed reference frame and with a resolution of 10 10 deg in latitude local time and 100 km in height including also a protonospheric component eight layers the data set contains the data from the international gps service igs with more than 100 ground gps stations worldwide distributed and the gps met low orbiting gps receiver both positive and negative elevation observations are used this means for each storm 1 000 000 of delays 400 occultations and 3000 unknowns per batch the international reference ionosphere and data coming from the ionosonde of the ebre observatory are used to show the reliability of the results