structural characterization of natural loess and remolded loess under triaxial tests this paper characterizes the microstructural evolution of saturated natural loess from a site in jingyang china during triaxial test along two stress paths for comparison the same soil in remolded state is also characterized mercury intrusion porosimetry mip scanning electron microscopy sem and environmental scanning electron microscopy esem were used for the microstructure investigation results show that the microstructure of natural loess is similar to that of remolded loess before the consolidated undrained cu triaxial tests including conventional triaxial compression ctc test and reduced triaxial compression rtc test on the contrary their microstructures are different after the tests deeper examination shows that loading led to a significant change of inter aggregate pores without modifying the intra aggregate pores in addition the volume of inter aggregate pores after the rtc test is greater than that after the ctc test under the same consolidation stress the microstructure features of natural and remolded loess after the tests are further used to analyze the macro mechanical behavior for better understanding the relationship between them the results show that it is the cementation bonds of which breakage is influenced by stress path and confining pressure that play important roles in the strength and deformation behavior

centrifuge model study on settlement of strip footing subject to rising water table in loess owing to man made activities and natural conditions the groundwater table experiences considerable changes in lanzhou centrifugal model tests were performed to investigate the settlement of strip

wetting induced collapse behavior associated with infiltration a case study abstract limited information is available in the literature for interpreting the influence of water infiltration process that contributes to in situ collapse in loess deposits for this reason the focus of the present investigation has been directed to studying the collapse deformation with respect to time in heifangtai china where significant wetting induced collapse deformation is widespread due to multiple years of irrigation activities a method that is based on easy to obtain parameters from constant water content oedometer tests and the wetting soil water characteristic curve is used for predicting the long term wetting induced collapse deformation the proposed method is validated using a field infiltration test the wetting induced collapse behavior in heifangtai is interpreted using the proposed method results of the study suggest that there is a significant difference in total subsidence between the irrigation and non irrigation areas the collapse in the irrigation area occurs during the period when the wetting front advances and the groundwater table gwt forms and rises until the formation of a new hydraulic equilibrium state which is significantly different from its initial condition however the collapse in the non irrigation area is mainly related to the gwt variation the difference in the total subsidence between the irrigation and non irrigation areas is predominantly associated with the propagation of the wetting front the proposed method is simple and can be extended in practical applications for reliably estimating the in situ collapse deformation associated with the water infiltration process

authigenic potassium feldspar a tracer for the timing of palaeofluid flow in carbonate rocks northern calcareous alps austria

tracking of polar cap ionospheric patches using data assimilation 1 ionospheric f region patches are 2 10 larger than background electron densities in the polar ionosphere the eiscat svalbard incoherent radar esr observed a sequence of patches between 2000 2200 ut on 12 december 2001 in this paper the source of these structures is investigated using several other data sets together with a convection driven trajectory analysis the data are assimilated into ionospheric data assimilation three dimensional ida3d the background model used is the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model ncar timegcm the trajectory analysis is based on maps of ionospheric convection obtained from the assimilative mapping of ionospheric electrodynamics amie in addition to patches a tongue of ionization toi is investigated it is shown that patches formed part of the toi it is tempting to conclude the toi and the patches originate at midlatitudes however the ida3d and trajectory analysis suggest that they were transported toward noon from the morning and afternoon sectors near 62 geographic latitude thus for this case the toi and patches did not originate at midlatitudes this work represents advances in the field of patch research a new capability to perform an analysis of patch origin and fate using three dimensional 3 d ionospheric assimilation and 2 d trajectory analysis codes is demonstrated for a sequence of patches observed 12 december 2001 the current resolution of the technique is not able to identify detailed patch formation mechanisms however by it can track the plasma back in time to locations and times where patch formation mechanisms operate

formation of polar cap patches associated with north to south transitions of the interplanetary magnetic field on january 15 1991 the sondrestrom incoherent scatter radar probed the midday high latitude ionosphere to gather evidence for the formation and entry of polar cap patches during the experiment the interplanetary magnetic field imf bz was positive and steady for few hours until 1548 ut when a short negative excursion of bz occurred prior to the bz excursion and when this parameter was directed northward the sondrestrom radar detected a quasi stationary density feature situated near the poleward boundary of the oval convergent electric fields and slightly elevated te values were seen accompanying the f region density feature a numerical model of the high latitude ionosphere that uses a steady north bz heppner and maynard convection pattern suggests that under these imf conditions a tongue of ionization toi can be formed near the midday sector but it is confined to the poleward boundary of the auroral oval it does not traverse into the polar cap this simulated bz northward toi resembles the density feature seen in the radar data prior to the bz negative excursion when the bz value was oriented southward the radar detected the density feature moving poleward and then disappearing to the north of the radar field of view at this time of bz negative the radar data also displayed elevated ti values and a new pattern of line of sight velocities nearly 34 min after the density feature departed from the field of view of the sondrestrom radar the qaanaaq digisonde measured a factor of 2 increase in the of2 values similar enhancements are typically attributed to the passage of a patch we also conducted a numerical simulation of the transit of the density feature from its initial location near the polar cap boundary up to its passage through the qaanaaq station the time that the density feature reaches qaanaaq in our simulations is in good agreement with the actual time that the enhanced patch like number density was observed at qaanaaq the bz switching mechanism does not dispute the validity of other patch formation mechanisms it merely suggests that a bz northward toi can end up as a polar cap patch if a timely reversal of bz occurs

direct observations of the evolution of polar cap ionization patches patches of ionization are common in the polar ionosphere where their motion and associated density gradients give variable disturbances to high frequency hf radio communications over the horizon radar location errors and disruption and errors to satellite navigation and communication their formation and evolution are poorly understood particularly under disturbed space weather conditions we report direct observations of the full evolution of patches during a geomagnetic storm including formation polar cap entry transpolar evolution polar cap exit and sunward return flow our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a tongue of ionization toi

ionospheric response to the corotating interaction region driven geomagnetic storm of october 2002 unlike the geomagnetic storms produced by coronal mass ejections cmes the storms generated by corotating interaction regions cirs are not manifested by dramatic enhancements of the ring current the cir driven storms are however capable of producing other phenomena typical for the magnetic storms such as relativistic particle acceleration enhanced magnetospheric convection and ionospheric heating this paper examines ionospheric plasma anomalies produced by a cir driven storm in the middle and high latitude ionosphere with a specific focus on the polar cap region the moderate magnetic storm which took place on 14 17 october 2002 has been used as an example of the cir driven event four dimensional tomographic reconstructions of the ionospheric plasma density using measurements of the total electron content along ray paths of gps signals allow us to reveal the large scale structure of storm induced ionospheric anomalies the tomographic reconstructions are compared with the data obtained by digital ionosonde located at eureka station near the geomagnetic north pole the morphology and dynamics of the observed ionospheric anomalies is compared qualitatively to the ionospheric anomalies produced by major cme driven storms it is demonstrated that the cir driven storm of october 2002 was able to produce ionospheric anomalies comparable to those produced by cme driven storms of much greater dst magnitude this study represents an important step in linking the tomographic gps reconstructions with the data from ground based network of digital ionosondes

on the entry and transit of high density plasma across the polar cap 1 observations are presented from superdarn and the eiscat svalbard radar of two intense polar cap patch events on 6 february 2001 the interplanetary magnetic field imf was dominated by a large positive by component and for both events the electron density exceeded 1012 m 3 in the f region with superdarn we tracked the events all the way across the polar cap from the dayside svalbard sector to the nightside alaska sector the flow speed was highly dynamic and pulsed and both patches underwent substantial rotation in the polar cap on the nightside the leading edge had become the trailing edge it suggests that the first patch to enter the polar cap on the dayside may not always be the first patch to reach the nightside plasma might be stagnant in the polar cap or even overtaken the study also provides evidence that momentum transfer in the dayside polar cap can last significantly longer than 10 min after reconnection especially for extremely long field lines where imf by is dominating i e on old open field lines knowledge of the solar wind driver and the coupling processes is therefore extremely important for predicting the motion of a polar cap patch event across the polar cap gradients in the plasma flow associated with the rotation of the extreme density may in itself lead to a stronger growth of ionospheric irregularities these irregularities may continue to grow all the way across the polar cap the result is more efficient creation of ionospheric irregularities

geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison abstract derbyshire e and mellors t w 1988 geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison eng geol 25 135 175 loess and loessic deposits cover some 630 000 km 2 of the surface of mainland china the loess plateau of shanxi shaanxi gansu and ningxia being the type region of this formation loess thickness generally exceeds 100 m over large areas of the loess plateau the maximum recorded thickness being 335 m in eastern gansu province near the city of lanzhou in britain loess and loessic deposits form part of a group of materials collectively known as brickearth they occur predominantly as sporadic accumulations in the southeast of england and rarely attain a thickness of more than four metres despite their geographical separation the deposits from china and britain have a remarkable similarity in some of their physical and geotechnical characteristics samples from both locations have been examined and tested in the laboratory and the results are presented the scope of the testing programme involved mineralogical analyses soil microfabric studies using a scanning electron microscope index testing including plasticity grading and density measurements and the investigation of the compressibility characteristics of the soils with particular reference to their susceptibility to collapse a soil structure model based on scanning electron microscope studies is presented and discussed in relation to the perceived mode of formation of the soils and their postdepositional history

on the symmetry of ionospheric polar cap patch exits around magnetic midnight in this paper we examine how polar cap patches which have been frozen into the antisolar flow over the polar cap are transported into the nighttime auroral oval first we present a detailed case study from 12 january 2002 with continuous observations of polar cap patches exiting into the nighttime auroral oval in the scandinavian sector satellite images of the auroral oval and all sky camera observations of 630 0 nm airglow patches are superimposed onto super dual auroral radar network convection maps these composite plots reveal that polar cap patches exit on both the dusk and on the dawn convection cells then we present statistics based on 8 years of data from the meridian scanning photometer at ny aalesund svalbard to investigate the possible interplanetary magnetic field imf by influence on the distribution of patch exits around magnetic midnight the magnetic local time distribution of patch exits is almost symmetric around magnetic midnight independent of imf by polarity synthesizing these observations with previous results we propose a three step mechanism for why patch material exits symmetrically around midnight first intake of patch material occurs on both convection cells for both imf by polarities second plasma intake by transient magnetopause reconnection stretches the newly cut polar cap patches into dawn dusk elongated forms during their transport into the polar cap and finally at exit dawn dusk elongated patches are split and diverted toward both the dawn and dusk flanks when grabbed by transient tail reconnection

multiradar observations of the polar tongue of ionization 1 we present a global view of large scale ionospheric disturbances during the main phase of a major geomagnetic storm we find that the low latitude auroral and polar latitude regions are coupled by processes that redistribute thermal plasma throughout the system for the large geomagnetic storm on 20 november 2003 we examine data from the high latitude incoherent scatter radars at millstone hill sondrestrom and eiscat tromso with superdarn hf radar observations of the high latitude convection pattern and dmsp observations of in situ plasma parameters in the topside ionosphere we combine these with north polar maps of stormtime plumes of enhanced total electron content tec derived from a network of gps receivers the polar tongue of ionization toi is seen to be a continuous stream of dense cold plasma entrained in the global convection pattern the dayside source of the toi is the plume of storm enhanced density sed transported from low latitudes in the postnoon sector by the subauroral disturbance electric field convection carries this material through the dayside cusp and across the polar cap to the nightside where the auroral f region is significantly enhanced by the sed material the three incoherent scatter radars provided full altitude profiles of plasma density temperatures and vertical velocity as the toi plume crossed their different positions under the cusp in the center of the polar cap and at the midnight oval polar cap boundary greatly elevated f peak density 1 5e12 m 3 and low electron and ion temperatures 2500 k at the f peak altitude characterize the sed toi plasma observed at all points along its high latitude trajectory for this event sed toi f region tec 150 1000 km was 50 tecu both in the cusp and in the center of the polar cap large upward directed fluxes of o 1 e14 m 2 s 1 were observed in the topside ionosphere

summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests this paper summarizes experimental studies on wetting induced collapsibility in loess using single oedometer double oedometer and triaxial wetting tests artificially structural loess samples with interparticle bonding calcite caco3 and a large void ratio were tested in the laboratory to avoid sampling disturbance of natural loess the comparison between the single and double oedometer tests confirms that the wetting induced deformation is independent of the sequence of wetting and loading the conventional triaxial apparatus was enhanced for investigating the collapse deformation in response to different water content increments when subjected to different stress levels the wetting induced strain subjected to high confining pressure develops in two steps it increases with increasing water content and reaches a relatively stable plateau and then increases rapidly again until a final stable state is reached the initial collapse surface was found by plotting the wetting induced strain vectors obser

investigating storm enhanced density and polar tongue of ionization development during the 22 october 1999 great storm we investigate large scale plasma density increases occurring during the 22 october 1999 great storm and focus on storm enhanced density sed and polar tongue of ionization toi development observations include two hourly global ionosphere map series coupled with multi instrument in situ space based and ground based data plots with super dual auroral radar network two cell convection maps and with model generated neutral wind vector maps results demonstrate the equatorial electrojet events occurring in the australian and american sectors the high density plasma features and their underlying plasma transportation processes during the main phase a series of four prompt penetration electric field ppef events occurred with subauroral polarization stream e field development forming a plasmaspheric drainage plume these e field events caused the repeated development of equatorial ionization anomaly eia sed bulge and sed plume during the local dusk midnight hours in those sectors that covered these local times showing a westward movement in accordance with their local time dependence the eia sed structure developed first in the american sector later on over the pacific and finally in the australian sector the sed plume plasma found its way into the polar cap through the dayside cusp region created in the north some large polar cap enhancements reaching up to seven times of the quiet time levels and evolved in each hemisphere into a polar toi we speculate that the enhanced growth of eia transporting high density solar produced plasma to the sed bulge via strong net eastward e field effects and the mechanical effects of equatorward neutral winds contributed to the polar toi s increasingly better development

cyclic variability in microstructure and physio mechanical properties of the xiashu loess palaeosol sequence in nanjing china abstract for the xiashu loess palaeosol sequence in nanjing china further to our work on the cyclic variability in its chemical composition and swelling shrinkage properties xia j huang g l liu z t chen x m 2007 cyclic variability in chemical composition and swelling shrinkage properties of the xiashu loess stratum near nanjing china pedosphere 17 5 666 672 this paper studies the cyclic variability in its microstructure and physico mechanical properties and the corresponding influence on its engineering behaviour for geotechnical and geological practices in addition the cyclic variability in the soil s grain size distribution and geochemical characteristics is compared with that of the loess palaeosol sequences at two other sites in china indicating a geographical pattern of cyclic variation of the sequences

global ionospheric response to the 2009 sudden stratospheric warming event using ionospheric data assimilation four dimensional ida4d algorithm a data assimilation algorithm is used to delineate the time dependent three dimensional ionospheric response to the 2009 sudden stratospheric warming ssw event we use the ionospheric data assimilation four dimensional ida4d algorithm to study the global ionospheric response to the 2009 ssw this is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere ionosphere coupling via tidal modifications during the 2009 ssw event model results reveal that the dominant mode of ionospheric variability during the 2009 ssw is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1 the ida4d results completely characterize the tidal perturbation during the 2009 ssw for the first time and show the global 3 d structure of the tide in total electron content tec and electron density the largest ionospheric responses were seen at low latitudes where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere the ionospheric response to the warming was characterized by an increase in tec in the morning early afternoon sector and a decrease during the late afternoon evening period the effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km the ida4d results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 ssw event we suggest that this could be a result of the equatorial fountain effect being further modified by the summer to winter meridional neutral winds

ionospheric storm time dynamics as seen by gps tomography and in situ spacecraft observations 1 during major geomagnetic storms anomalous enhancements of the ionospheric density are seen at high and middle latitudes a number of physical mechanisms have been invoked to explain these storm time density anomalies including an expansion of high latitude electric plasma convection to midlatitudes thermospheric neutral winds and changes in the ionospheric composition however it remains unclear which mechanism plays the dominant role in the formation of storm time density anomalies partly because of insufficient coverage of the measurements of global electric convection and thermospheric winds at midlatitudes this paper describes a novel technique for extracting the storm time e b convection boundary from in situ measurements of plasma bulk motion obtained by leo dmsp satellites the convection boundary estimated from the dmsp data during major magnetic storm of 20 november 2003 has been compared with the global distributions of the ionospheric plasma deduced from characteristics of gps signals acquired by a ground based network of gps receivers the tomographic inversion of gps data using a three dimensional time dependent inversion technique reveals the spatial and temporal evolution of the storm time density anomaly comparison between the tomographic reconstructions of the ionospheric plasma distributions and in situ dmsp measurements of plasma bulk motion suggests that the convective flow expanded low enough in latitude to encompass in part the formation of the midlatitude tec anomaly some features of the tec dynamics observed during the 20 november 2003 storm however suggest that mechanisms other than the expanded ionospheric convection such as thermospheric neutral winds are also involved in the formation of the midlatitude anomaly

behaviour and engineering implications of recent floodplain soft soil along lower reaches of the yangtze river in western nanjing china recent floodplain soft soil is widespread along the lower reaches of the yangtze river in western nanjing china an area of new residential development and underground space utilisation such as subway lines and tunnels under rivers in nanjing city construction experience in this area in the last two decades shows that ground and underground engineering are susceptible to accidents the accidents are fundamentally due to the lack of a clear and detailed understanding of the geotechnical and geological properties in particular the differential consolidation settlement of the soft soil in this context this paper studies the behaviour and engineering implications of such soil first we present the soil s geological background and sedimentary features test its geotechnical properties and identify its material composition by x ray diffraction and sem then we investigate changes of microstructure at different depths and under different applied loadings and corresponding engineering implications under consolidation and compression finally by referring to a microstructure classification system for marine sediment we suggest a combined type of microstructure for the floodplain soft soil

geotechnical characterization and collapsibility of a natural dispersive loess abstract during preliminary investigation phase of the national chabahar zahedan railway line serious geotechnical problems including non uniform settlements tensile cracks and local collapse were reported in parts of the path near the coastline a follow up field investigation revealed that the in situ soil at construction site has a metastable structure being sensitive to saturation and loading therefore a comprehensive series of physical chemical electro chemical and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state the natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics given its significant collapse potential the soil was assigned into the category with severe trouble for construction purposes importantly our tests revealed that a threefold reduction in pore water salinity results in 4 rise in collapse potential of similar specimens reduction in salt concentration increases the thickness of diffuse double layer and hence collapsibility in addition strain softening shear behavior was observed for elevated confining stresses under undrained triaxial stress state in fact this brittle type failure mechanism associated with continuous generation of pore water pressure is undesirable as catastrophic failures could happen with no advance warning

average characteristics and activity dependence of the subauroral polarization stream 1 data from the millstone hill incoherent scatter radar taken over two solar cycles 1979 2000 are examined to determine the average characteristics of the disturbance convection electric field in the midlatitude ionosphere radar azimuth scans provide a regular database of ionospheric plasma convection observations spanning auroral and subauroral latitudes and these scans have been examined for all local times and activity conditions we examine the occurrence and characteristics of a persistent secondary westward convection peak which lies equatorward of the auroral two cell convection individual scans and average patterns of plasma flow identify and characterize this latitudinally broad and persistent subauroral polarization stream saps which spans the nightside from dusk to the early morning sector for all kp greater than 4 premidnight the saps westward convection lies equatorward of l 4 60 invariant latitude spans 3 5 of latitude and has an average peak amplitude of 900 m s in the predawn sector saps is seen as a region of antisunward convection equatorward of l 3 55 spanning 3 of latitude with an average peak amplitude of 400 m s

deducing storm time f region ionospheric dynamics from 3 d time varying imaging 1 the inversion algorithm for estimating model parameters from ionospheric reverse engineering empire has been created to gain insight into ionospheric dynamics particularly when direct measurement is unavailable we extend the capabilities of empire here in order to demonstrate its effectiveness on densities obtained from real data we apply this method to real ionospheric data assimilation 4 dimensional ida4d data from storm time measurements focusing on the midlatitude f2 layer empire is used to estimate midlatitude field aligned and field perpendicular drifts the estimated upward drifts from empire are validated against measurements obtained from the millstone hill incoherent scatter radar zenith antenna the horizontal drifts are compared to the assimilative mapping of ionospheric electrodynamics amie model which estimates drifts from data sources independent of those used in ida4d results show that the direction and magnitude of the drifts and therefore the electric fields may be deduced from imaging based primarily on total electron content data although altitude variation is not significantly discernible we also indicate that the initial uplift of the storm enhanced density may have been more strongly influenced by field aligned contributions of neutral winds and diffusion than the electric fields

temporal variation in the permeability anisotropy behavior of the malan loess in northern shaanxi province china an experimental study by analyzing a fresh soil section and soil samples from yan an new area northwest china an engineering shallow loess slope was investigated temporal variation in the saturated horizontal hydraulic conductivity kh and saturated vertical hydraulic conductivity kv of loess samples were measured using variable head permeability tests the kh and kv values indicate that the loess exhibited permeability anisotropy in space and time and kh and kv at different depths decreased as seepage time increased kh time showed an exponentially decreasing trend and kv time showed a linearly decreasing trend analysis of the initial state and micromorphological features of the loess indicate that the orientation of soil particles in the deposition process may be inherently anisotropic the kh and kv values of the loess tended to decrease with depth as described by an exponential decay model

dynamic temporal evolution of polar cap tongue of ionization during magnetic storm 1 during a magnetic storm on 14 16 december 2006 a polar cap tongue of ionization toi was detected by an all sky imager asi at resolute bay canada 74 73 n 265 07 e we investigate the temporal evolution and spatial structure of the toi in detail by combining the optical data with other observations e g solar wind gps total electron content superdarn and dmsp and noaa poes satellites the toi was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm this interval corresponded to a period of prolonged stable large amplitude southward imf during a coronal mass ejection cme one to one and a half hours before the appearance of toi the polar cap boundary expanded rapidly far equatorward and a positive ionospheric storm occurred this implies that both the expansion of the high latitude plasma convection and build up of the source plasma in the midlatitudes are necessary conditions for the formation of a toi because both of them were triggered by a major southward turning of the imf the prolonged large amplitude southward imf orientation in the trailing part of the cme was primarily responsible for the generation of toi after its appearance the toi exhibited dynamic motion in the dawn to dusk direction simultaneous superdarn data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion the optical toi was found to be a continuous stream elongated in the noon midnight direction although it contained some mesoscale patterns absence of large scale temporal changes in the cusp plasma flow during the stable imf period allowed the toi to remain continuous without being broken into polar cap patches the mesoscale structures within the toi were probably produced by small scale velocity fluctuations in the cusp plasma flow the toi as visualized with the all sky airglow imager was found to be much more dynamic and much more complicated than we ever thought the current study indicates that such a behavior of the toi was presumably caused by a combination of temporal variations in the global scale plasma circulation system expansion and contraction of the polar cap area and plasma density changes in the dayside low to midlatitudes

transformation of high latitude ionospheric f region patches into blobs during the march 21 1990 storm discrete f region electron density enhancements of a factor of 2 or more have been observed in the high latitude ionosphere these enhancements have been termed patches if they occur within the polar cap and blobs if they occur outside of the polar cap it is important to understand the formation and evolution of these structures because they are associated with large phase and amplitude scintillation in transionospheric radio signals blobs are generally thought to result from the breakup of patches as they exit the polar cap however this process has not previously been observed detailed study of high latitude ionospheric plasma transport is generally difficult because of the sparseness spatial and temporal of electron density and velocity observations in this paper we present electron density enhancements measured from the qaanaaq digisonde the millstone hill incoherent scatter radar and the dmsp f8 satellite during a 5 hour interval of the march 21 1990 storm period and show definitively how a patch is transformed into a blob we present a new trajectory analysis package that is capable of using ionospheric convection patterns to determine the motion of ionospheric plasma over a period of several hours the new package uses convection patterns from the assimilative mapping of ionospheric electrodynamics amie technique to track the motion of observed patches from one site to another and thus determines where the measured electron density enhancements originated and where they went after being observed the trajectory analysis also establishes that there is a direct connection between the enhancements observed by the different instruments at different locations in this case within 4 hours plasma observed by a digisonde near the pole is convected through 35 of latitude to the northeastern united states where it is observed by the millstone hill radar then roughly equal portions are transported westward to alaska and eastward to scandinavia where they are observed by the dmsp satellite this study demonstrates that the changing convection pattern can significantly distort the patch shape and trajectory and illustrates the high degree of mixing of ionospheric plasma by convection the changing convection pattern leads to the simultaneous existence of a boundary blob and a subauroral blob which are both observed by the millstone hill radar this work is very relevant to our future ability to specify and forecast ionospheric conditions at high latitudes it represents a critical step from a merely qualitative ability to model the evolution of patches and blobs to a quantitative ability

storm time plasma transport at middle and high latitudes associated with the large scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions solar produced f region plasma is transported to and through the noontime cleft from a source region at middle and low latitudes in the afternoon sector as a result of the offset between the geomagnetic and geographic poles the afternoon sector region of strong sunward convection is shifted to increasingly lower geographic latitude throughout the interval between 12 ut and 24 ut a snowplow effect occurs in which the convection cell continually encounters fresh corotating ionospheric plasma along its equatorward edge producing a latitudinally narrow region of storm enhanced plasma density sed and increased total electron content which is advected toward higher latitudes in the noon sector the millstone hill incoherent scatter radar regularly observes sed as a spatially continuous large scale feature spanning local times between noon and midnight and at latitudes between the polar cap and its mid or low latitude source region for local times away from noon the latitude of most probable sed occurrence moves equatorward by 6 for an increase of 2 in the kp index during strong disturbances the topside sed is observed to be convecting sunward at 750 m s 1 with a flux of 1014 m 2 s 1 this feature accounts for the pronounced enhancement of ionospheric density near dusk at middle latitudes observed during the early stages of magnetic storms called the dusk effect and constitutes a source for the enhanced f region plasma observed in the polar cap during disturbed conditions

formation and development of the structure of collapsing loess in china abstract gao g 1988 formation and development of the structure of collapsing loess in china eng geol 25 235 245 it is well known that in china the regional variations in microstructure of loess are in phase with the overall tendency for collapsibility gradually decreasing from the northwest to the southeast these differences are consistent with variations in climatic conditions this indicates that the structure of collapsing loess is closely related to the climatic condition and geological environment based on the microstructure analyses it can be assumed that the formation and development of the structure of collapsing loess in china has undergone five stages the loessization stage the formation stage the development stage the degeneration stage and the clayization stage the five stages of loess regularly exist in different regions of the loess plateau this also shows that under the modern climatic condition the collapsing loess in the northwest of the loess plateau in china is still developing however the feature of collapsing loess is gradually disappearing in the southeast of the loess plateau

the distribution and geotechnical properties of loess soils lateritic soils and clayey soils in china in china various soils covering vast regions occur loess soils of the yellow river in northern china lateritic soils in southern china and clayey soils in central china the special geotechnical properties of these soils are briefly described the relationship of their material components and microstructural features with their geotechnical properties is studied it is shown that the special geotechnical properties of these soils depend mainly on their material component and microstructural features the distribution of these soils is studied in relation to geographical environment and climatic conditions it is suggested that the formation of the geotechnical properties of these soils have undergone three different development stages

collapsibility composition and microfabric of the coastal zone loess around the bohai sea china abstract coastal loess is a special loess deposit that is distributed around the bohai sea the primary objective of this study was to investigate the physical index mineralogical characteristics and collapse potential of coastal loess the secondary objective was to survey the effect of fine silt particles particle size 5 10 m 6 64 7 64 on the collapse process we tested the specific gravity moisture content dry density atterberg limits grain size distribution mineralogy and collapsibility characteristics in a laboratory generated scanning electron microscopy sem images and performed mercury intrusion porosometry mip tests the results of this investigation indicated that coastal loess has a moderately severe collapse potential the collapsibility coefficient decreases with an increase in the initial water content it initially increases and then decreases with an increase in vertical pressure as revealed by the mip test the collapse produces a smaller porosity and the middle pores are primarily responsible for the collapse the relationship of the collapsibility coefficient and particles with a diameter 7 64 have the same tendency in terms of their effect on collapse these results and analyses are important to improve the engineering construction safety in coastal zone loess areas and achieve a better understanding of loess properties compared with loess from a typical loess paleosol section

evidence against the dorag mixing zone model for dolomitization along the wisconsin arch a case for hydrothermal diagenesis ordovician carbonates near the wisconsin arch represent the type locality in ancient rocks for the dorag or mixing zone model for dolomitization field petrographic and geochemical evidence suggests a genetic link between the pervasive dolomite trace mississippi valley type mvt minerals and potassium k silicate minerals in these rocks which preserve a regional hydrothermal signature constraints were placed on the conditions of water rock interaction using fluid inclusion methods cathodoluminescence and plane light petrography stable isotopic analyses and organic maturity data homogenization temperatures of two phase aqueous fluid inclusions in dolomite sphalerite and quartz range between 65 and 120c freezing data suggest a na ca mg cl h2o fluid with salinities between 13 and 28 wt nacl equivalent the pervasive dolomitization of paleozoic rocks on and adjacent to the wisconsin arch was the result of water rock interaction with dense brines at elevated temperatures and it was coeval with regional trace mvt mineralization and k silicate diagenesis a reevaluation of the dorag mixing zone model for dolomitization in conjunction with convincing new petrographic and geochemical evidence has ruled out the dorag model as the process responsible for pervasive dolomitization along the wisconsin arch and adds to the abundant body of literature that casts serious doubt about the viability of the dorag model in general

k ca ar systematics of authigenic sanidine from waukau wisconsin and the diffusivity of argon authigenic sanidine occurs in almost monomineralic beds in the basal st peter sandstone near waukau wisconsin the high purity of this k feldspar indicates that it formed at low temperature either contemporaneously with deposition or during later diagenesis k ca analyses of two samples from the same bed yield discordant ages of 436 4 and 407 3 ma because sup 40 ca loss is unlikely at the low temperatures to which these minerals have been subjected these ages are interpreted as the times of formation of the sanidine both ages are younger than the estimated stratigraphic age of the st peter sandstone k ar analyses of splits of these same two samples give ages of 402 and 377 ma respectively these ages are lower by about 8 than the k ca ages because of the diffusive loss of radiogenic argon over geologic time an estimate of the diffusion coefficient for argon in the sanidine on the basis of the differences between the k ca and k ar ages suggests that diffusion of argon is about five orders of magnitude faster at low temperatures than an extrapolation of high temperature experimental data would indicate comparison of k ca and k ar ages may be useful in general for distinguishingmore diffusive loss from recrystallization events in feldspars less