interferometer studies of equatorial f region irregularities and drifts a radar interferometer technique developed at jicamarca peru and first used to study electrojet irregularities has now been used successfully to study plasma turbulence in the equatorial f region our first results have shown that the most turbulent echoes appear to come from a region that extends for tens of kilometers in altitude but for only a kilometer or less in the east west direction this slab may very well be the wall of a depleted region a plasma bubble sometimes the irregularities can be tracked as they move eastward or westward velocity profiles for the evening period obtained in this way show a strong shear with westward velocities at the lowest altitudes observed and eastward velocities above a plausible explanation for this shear is that the westward drifts are driven by electric fields produced by westward e region winds and mapped up along magnetic field lines while at higher heights where the electron density is greater the drifts are controlled by the f region dynamo driven by eastward winds

3d simulation of tbm excavation in brittle rock associated with fault zones the brenner exploratory tunnel case abstract brittle fault zones represent a major challenging geological environment for tbm tunnelling in deep alpine tunnels particularly when the faults are near parallel to or cross the tunnel axis at a low angle this is the case of the brenner exploratory tunnel in italy serious local instabilities occurred at the left side wall during tbm drive in the granitic rocks associated with a sub vertical fault zone parallel to the tunnel axis the segmental lining was collapsed at a distance of more than 2d d is tunnel diameter behind the face without any evidence the deformation and failure then propagated intensively to nearby previously stabilized sections with a length of approximately 60 m in the longitudinal direction leading to a subsequent damage of the shields and grippers of the machine and to a stoppage of the excavation in almost 4 months to deal with these severe geotechnical problems encountered when tunnelling through a fault zone a realistic 3d numerical simulation based on a site investigation and characterisation of the fault zone can provide a helpful decision aid as they give a quantitative assessment of the potential mode of failure in the case of the brenner exploratory tunnel the behaviour of the rock mass is neither ductile nor brittle but governed by the combination due to the presence of the brittle fault zone this paper focuses on the 3d simulation of such complex failure evolution special emphasis is placed on the modelling of the fault zone and of the tbm excavation process the results demonstrate the role that the local rock mass condition and the complex interaction between the rock mass the tbm components and the tunnel support play on the characterization of this instability phenomenon

high resolution oi 630 nm image measurements of f region depletion drifts during the guara campaign a high performance all sky imaging system has provided data on the evolution and drift motions of f region depletions above the magnetic dip equator at alc ntara brazil 2 3 s 44 5 w monochromatic images of depletions in the oi 630 nm nightglow were recorded on eight nights during 1 16 october 1994 as part of the guara campaign the drift motions of the depletions were typically 80 100 m s eastward prior to local midnight and reduced to a minimum of 30 50 m s in the morning hours in accord with previous observations however on october 2 3 and 12 13 the depletions were observed to reverse direction for 60 90 min achieving westward speeds of 30 m s before the motion reverted to eastward around 0100 lt and accelerated to 35 45 m s near dawn magnetic activity and other evidence suggests that these reversals in the motion of the airglow depletions probably result from reversals in the f region dynamo rather than from shifts in the altitude of the shear in the nighttime f region plasma drift

dam to delta sediment inputs and storage in the lower trinity river texas livingston dam on the trinity river in se texas usa disrupts the transport of sediment to the lower trinity river and the trinity bay galveston bay estuary however a sediment budget of the lower basin shows that the effects of this disruption are undetectable in the lower river sediment trapped in lake livingston is partly offset by channel erosion downstream of the dam and by inputs from the lower basin most importantly however the lower coastal plain reaches of the trinity are characterized by extensive alluvial storage and are a bottleneck that buffers the bay from effects of upstream changes in sediment flux storage is so extensive that the upper trinity basin and the lowermost river reaches were essentially decoupled in the sense that very little upper basin sediment reached the lower river long before the dam was constructed whereas sediment storage in lake livingston is extensive alluvial storage on the trinity flood plain is even more extensive dam related sediment starvation effects are noted for about 52 km downstream and the sediment budget suggests that a majority of the sediment in this reach is likely derived from channel scour and bank erosion the capacious alluvial storage in the lower trinity not only limits flux to the bay but the large amount of remobilizable alluvium also allows the system to adjust to localized sediment shortages as illustrated in the dam to romayor reach internal adjustments within the lower trinity river valley thus buffer the bay from changes in sediment supply upstream

geomorphic and vegetative characteristics along three northern virginia streams geometry sediment and woody vegetation data were collected from bottomland geomorphic surfaces at valley sections along three gaged perennial streams of northern virginia the basins of the streams differ widely in topography and physiography mean discharges vary from 0 196 to 323 m3 per sec prevalent surfaces identified were the depositional bar the active channel shelf the flood plain and terraces the stages corresponding to active channel shelf levels were equivalent to flow durations of 5 to 13 stages corresponding to flood plain levels were equivalent to discharges with 1 4 to 2 0 yr recurrence intervals the discharge data and statistical tests of geomorphicsurface sediment and vegetative data suggest that the various alluvial features are formed and maintained by hydraulically controlled sorting processes analysis of woody plant and geomorphic data shows that each surface supports characteristic species some of which are nearly unique to a surface tests of sediment type with species distribution showed lower correlation than that of geomorphic surface with species it is inferred that plant distributions largely are controlled by flow frequency and intensity and that plants may help to identify geomorphic levels and potential for flood damage

ionospheric conditions affecting the evolution of equatorial plasma depletions model studies have been carried out to specify the ionospheric conditions and electrodynamical processes required to describe the geometry of westward tilting and bifurcating equatorial plasma depletions inferred from airglow imaging measurements taken on ascension island in early 1981 the results indicate that if the westward tilts are to be associated with eastward plasma drifts that decrease with altitude above the f peak this shear must be set up by a zonal wind pattern of decreasing speed at increasing distances from the equator below the peak calculations of flux tube integrated pedersen conductivity including both e and f region contributions are in agreement with the simulations of zalesak et al 1982 that show bifurcated depletions to be associated with a mild gradient in the bottomside conductivity profile

effect of rock mass and discontinuity mechanical properties and delayed rock supporting on tunnel stability in an underground mine abstract in this paper the rock mass stability around the tunnels in an underground mine is investigated using the distinct element method a three dimensional model was developed based on the available geological geotechnical and mine construction information it incorporates the inclined lithologies including a weak interlayer the persistent and non persistent faults and a complex tunnel system the strain softening constitutive model was prescribed for the rock masses in the numerical model the continuously yielding joint model was used to describe the non linear behavior of the faults to account for the deformations occurred between the excavations and rock supporting the delayed installation of supports was implemented by using the stress relaxation method numerical analyses were performed to study the effects of the post failure constitutive parameters of the rock masses the mechanical properties of faults and the delayed supporting on tunnel stability the following results are presented a the rock mass deformations and failure zones around the excavations b the joint shear displacements of the major fault and c the failure conditions of the applied supports satisfactory comparisons are obtained between the predictions based on numerical modeling and the field deformation measurements the analysis procedures presented in this study are applicable for stability assessment of various underground rock excavation projects located in different parts of the world having different geological settings and complex engineering situations

first detection of the supersonic upward plasma flow structures in the early morning sector we present the first observations of the supersonic updrafting plasma drifts in the predawn sector two dmsp satellites quasi simultaneously detected two fast speed events one of 385 km spatial extension and with the maximum upward velocity of 1683 m s appeared at 3 lt and the other of 1500 km large with maximum speed of 1770 m s occurred at 5 lt both supersonic structures were observed above the eastern pacific region separated by 35 of longitude in space and by 45 min in time the events occurred at the recovery phase of the geomagnetic storm of 19 february 2014 during rapid oscillations of the interplanetary magnetic field b z and the interplanetary electric field e y components which increased the eastward electric field in the equatorial nighttime ionosphere and triggered the generation of plasma irregularities the storm time penetration electric fields seem to be the principal driver of the observed supersonic events

sheet erosion rates determined by using dendrogeomorphological analysis of exposed tree roots two examples from central spain this paper describes the determination of sheet erosion rates by using dendrogeomorphological methods on exposed tree roots two sites on the northern slope of the guadarrama mountains central spain were studied a popular trail in a scots pine forest senda schmidt valsain growing on granites and gneisses and an open holm oak forest on granitic slopes monterrubio these sites were selected because they showed high denudation morphologies due to accelerated soil erosion processes caused by human influence trampling by continuous trekking and overgrazing resulting in exposed roots the method applied is based on the morphological pattern of roots defined by the growth ring series of the sampled roots in order to confirm the validity of the criteria used and to make the estimations of erosion more accurate several anatomical indicators of exposed and non exposed pinus sylvestris roots were characterized the study entailed a statistical analysis of exposure time and erosion depth the influence of environmental factors affecting the variation in velocity of the erosion processes was also examined

equatorial ionospheric plasma bubble irregularity occurrence and zonal velocities under quiet and disturbed conditions from polarimeter observations amplitude scintillation and faraday rotation angle fluctuations of satellite vhf beacons registered by electronic polarimeters operated at two stations spaced 110 km apart in the magnetic east west direction namely cachoeira paulista 22 41 s 45 w dip angle of 26 and sao jose dos campos 23 12 s 45 51 w dip angle of 26 in brazil are analyzed for equinoctial and summer months of 1982 1983 to determine the irregularity patch occurrence characteristics and their zonal velocities under varying levels of magnetic disturbances the scintillation patch occurrences and total electron content fluctuations representing plasma depletion structures decrease during premidnight hours and are enhanced in the postmidnight period the occurrences often extend to morning hours with increasing magnetic activity index while the night events are associated with eastward irregularity patch motion the morning events have westward velocities the reversal occurring around 0400 lt reflecting the morning velocity reversal in the f region bulk plasma motion reported earlier from jicamarca radar measurements the westward plasma bubble motions reported here represent the first observation of this kind another important finding from the present investigation is a clear tendency for the zonal plasma motion namely the equatorial meridional electric field to become enhanced mainly in the premidnight hours immediately following strong magnetic activity

the headward extent of fluvial landforms and associated vegetation on massanutten mountain virginia variation in fluvial landforms and associated vegetation in the headward upstream direction has received little study and the controlling factors are not well understood the relations among channel gradient basin area stream order and the headward extent of fluvial landforms and vegetation was studied in 18 small basins and larger nearby stream reaches in the massanutten mountain area northern shenandoah valley virginia low order streams were traversed to their basin heads notice was made of the point or region of the disappearance of fluvial landforms indicator species were used to confirm landform identification the studied landforms include the channel bar channel shelf floodplain and terraces basin geomorphic characteristics were determined from topographic and geologic maps and ground surveys results suggest that gradient is the most important factor controlling the development of fluvial landforms floodplains have not developed along stream reaches where average channel gradients exceed 0 15 channel shelves and associated vegetation occur farther upstream than floodplains

hydrologic inferences from tree ring studies on the hawkesbury river sydney australia abstract introduced salix trees in australian alluvial environments can be used to make a number of hydrologic inferences dendrochronological studies along the hawkesbury river near windsor suggest that the salix growth form and annual growth ring variability are closely associated with the local hydrologic regime detailed analyses of 33 trees showed that tree growth is suppressed close to water and increases with height above mean low stage levels because of the decreasing influence of flooding alluvial levels contain discrete vegetation patterns and growth characteristics that are not explained by variations in soil and climate growth of salix in thickets on low in channel benches is flood limited with fitted exponential growth curves having positive or zero slopes the high in channel bench contains vegetation influenced by flooding but growing according to classical exponential decay functions trees on floodplain levees show full canopy development and the most rapid growth because of fertile soils the high availability of water and limited influence of floods overtopping levee tops elevation and tree growth relations are used to develop a relation between growth and flood frequency this is applicable to catchments of similar size soil type and climate analyses of tree form and root distribution indicated that dendrochronological techniques may be used to determine the minimum land surface age and rates of accretion around the tree bole in alluvial areas of southeastern australia

soil deformation measurement using particle image velocimetry piv and photogrammetry a deformation measurement system based on particle image velocimetry piv and close range photogrammetry has been developed for use in geotechnical testing in this paper the theory underlying this system is described and the performance is validated digital photography is used to capture images of planar soil deformation using piv the movement of a fine mesh of soil patches is measured to a high precision since piv operates on the image texture intrusive target markers need not be installed in the observed soil the resulting displacement vectors are converted from image space to object space using a photogrammetric transformation a series of validation experiments are reported these demonstrate that the precision accuracy and resolution of the system are an order of magnitude higher than previous image based deformation methods and are comparable to local instrumentation used in element testing this performance is achieved concurrent with an order of magnitude increase in the number of meas

thirty sixth canadian geotechnical colloquium advances in visualization of geotechnical processes through digital image correlation1 digital image correlation dic is an image processing technique that calculates fields of incremental displacement by comparing two digital images and locating numerous small regions in both image

floodplain dynamics of a wandering river dendrochronology of the morice river british columbia canada dendrochronological techniques are used to develop a history of flood occurrence and relative stage for the middle section of the morice river based on flood scars bank undercutting dates and tree establishment dates on fluvial features the morice river is the major tributary of the bulkley river skeena river system northwest british columbia canada reach 2 of the morice river drainage area 3499 km2 is forested and little disturbed by human activity it is presently a wandering multiple channel river and shows evidence of frequent channel changes which have reworked most of the floodplain several times in the last 180 years airphoto analysis and dendrochronology demonstrate that many channels show evidence of two or more periods of activity reoccupation and re excavation of pre existing channel segments is more frequent than development of new channels thirty one significant floods over the past 105 years were detected through dendrochronology of flood scarred trees on the morice river flood scars are predominantly caused by flood transported logs abundant log transport results in damage to channel margin trees during events only slightly above bankfull discharge the record of flood scars on channel margin trees and establishment dates of forest stands on abandoned channels and surfaces show that the morice river has maintained its present regimen for the past 115 years during the neoglacial the morice river was more active than in recent times and its channels occupied twice the present area tree establishment dates show that neoglacial surfaces and channels of the morice river were abandoned during the 1820 s the modern floodplain configuration was assumed by 1870

erosion rates and sediment budgets in vineyards at 1 m resolution based on stock unearthing burgundy france abstract a new and simple method is developed to efficiently quantify erosion and deposition rates based on stock unearthing measurements this is applicable to spatial scales ranging from plot to hillslopes and to time scales ranging from single hydrologic events to centennial scales the method is applied to a plot area on vineyard hillslopes in burgundy monthelie france with measurement of 4328 vine plants a sediment budget established at the plot scale shows a mean soil lowering of 3 44 1 cm over 20 years involving a minimal erosion rate of 1 7 0 5 mm yr 1 locally erosion rates can reach up to 8 2 0 5 mm yr 1 this approach allows the sediment redistribution to be mapped and analyzed at 1 m resolution it provides novel insights into the characterization of erosion patterns on pluri decennial scales and into the analysis of spatial distribution of erosion processes on cultivated hillslopes

global positioning system measurements of the ionospheric zonal apparent velocity at cachoeira paulista in brazil ionospheric irregularities and their zonal apparent drift were studied using global positioning system gps measurements at cachoeira paulista 22 41 s 45 00 w 26 dip angle in brazil during november 6 19 1998 radio scintillations at the gps l1 frequency 1 575 ghz were monitored using four gps receivers spaced geomagnetically east west and north south total electron content tec was measured through the ionospheric advance of the gps l1 and l2 1 227 ghz phases strong amplitude scintillations coincided with tec fluctuations associated with spread f bubbles elongated along the magnetic field movement of the presnel scale 400 m ionospheric irregularity layers caused the scintillation to drift and their zonal apparent drift velocities were measured using a cross correlation technique our measurements show that the apparent eastward velocity varies from 200 m s to 150 m s at 2000 lt and then it decreases to 100 50 m s at midnight on a magnetically disturbed day reversal of the zonal apparent drift was observed just after midnight and the apparent westward velocities observed at early in the morning showed large variations with location in the sky from the receivers spaced in the geomagnetic north south direction we measured near zero time shifts from which we conclude that the correlation length of several hundred meter scale irregularities is much larger than 70 m separation between the north and south receivers

3d characterization of microbially induced carbonate precipitation in rock fracture and the resulted permeability reduction abstract a new seepage control method for fractured rock is biogrouting through a microbially induced calcite precipitation micp process a study on the spatial distribution of biogrout in a rock fracture and its effect on permeability reduction is presented in this paper a series of experiments together with 3d scanning and 3d flow simulation were performed on rock fractures with various initial apertures treated by bio grouting a lognormal distribution of micp precipitates along the flow direction in a fracture was observed the 3d flow simulation of biogrouted fracture has revealed that the routinely adopted parallel plate model cubic law for estimating permeability of channel flow is no longer applicable when the fracture aperture is less than the critical value of 0 7 mm based on this study this is because partially clogging will occur when the fracture aperture is less than the critical value resulting in a transition of the flow type from surface flow to channel flow a semi empirical equation which can account for the effect of flow type has been proposed for estimating the permeability reduction due to bio grouting for rock fractures

ionospheric scintillation observations at natal we report ionospheric scintillation observations made at natal brazil during a period of 2 years the nighttime scintillations of satellite signals at 250 mhz commonly exceeded 20 db peak to peak seasonally it showed a typical behavior for the south american sector with a single peak centered around october november months and the local evening hours of 2100 2300 lmt this seasonal behavior was different from that of the african sector and very different from that of the pacific sector on a spacing of 278 m the eastward irregularity drift speed was measured by the method of similar fades this together with the determination of fresnel frequency from the power spectrum analysis was used to calculate the height of the irregularity patch a value of 294 km was obtained multisatellite scintillation observations indicated that even though the initiation of an irregularity cloud commonly occurred earlier on signals transmitted by the eastern satellite there were substantial cases when the reverse was observed one case which was analyzed in detail suggested that the irregularity clouds formed independently along two radio paths separated by 520 km

ionospheric zonal velocities at conjugate points over brazil during the copex campaign experimental observations and theoretical validations 1 we analyze in detail the zonal velocities of large scale ionospheric plasma depletions over two conjugate stations inferred from oi 630 nm airglow all sky images obtained during the conjugate point equatorial experiment copex campaign carried out in brazil between october and november 2002 the conjugate stations were boa vista bv geogr 2 8n 60 7w dip angle 22 0 n and campo grande cg geogr 20 5s 54 7w dip angle 22 32 s over campo grande the zonal velocities were measured also by a system of spaced gps scintillation receivers the airglow zonal velocities at the conjugate sites were seen to agree very closely except for a slightly increased velocity over cg which we attribute to the presence of the geomagnetic anomaly the results show a high degree of alignment of the bubbles along the geomagnetic field lines during the bubble development phase and as the bubbles travel eastward thereby suggesting that the neutral zonal wind effect in the zonal plasma motion is an integrated effect along the flux tube the zonal velocities obtained from the gps technique were always larger than those calculated by the airglow technique which permitted observation of zonal plasma velocity shear between the altitudes of the airglow emitting layer and of the gps scintillation theoretical ambient plasma zonal velocities calculated using the formulations by haerendel et al 1992 and eccles 1998 are compared with the experimental results our results also reveal some degree of dependence of the zonal velocities on the solar flux f10 7 and magnetic kp indices during the copex period

on the latitudinal variations of the ionospheric electric field during magnetospheric disturbances a joint alert campaign was organized during the month of october 1980 by the incoherent scatter radars in the american sector namely jicamarca arecibo millstone hill and chatanika the campaign which met with success was designed to study the behavior of the ionospheric electric field as a function of latitude during magnetically active conditions the arecibo data in this campaign support present and previous observations at jicamarca that suggest that when the convection e field suddenly decreases the alfven layer shielding field becomes unbalanced and penetrates the plasmasphere while this type of observation is reasonably convincing others are more difficult to categorize we suggest that beside the high latitude electric fields time varying auroral conductivity models will have to be considered in order to understand the morphology of the low latitude e field disturbances we present the first correlation analysis and determination of the amplitude ratio of the disturbed zonal electric field at 30 geometric latitude arecibo to the field at 0 jicamarca other highlights of the paper are a discussion of dp2 which may help clarify the controversy surrounding it and a discussion of the sensitivity of low and mid latitude radars to disturbances of magnetospheric origin we show that this sensitivity maximizes at the magnetic equator

f region east west drifts at jicamarca f region east west drifts have been measured at jicamarca for almost 10 years using incoherent scatter the drifts are westward during the day and eastward at night the daytime drift velocities are about 50 m s and change very little with season or solar cycle the evening reversal occurs at about 1600 local time throughout the solar cycle the maximum nighttime eastward drifts are about 105 and 130 m s during solar minimum and maximum respectively the daytime and nighttime drifts show very litle variation with magnetic activity these jicamarca incoherent scatter results especially the reversal times differ appreciably from results obtained using other techniques but there appear to be fairly simple explanations for the apparent disagreements

airglow characteristics of equatorial plasma depletions a new low light level all sky 6300 a airglow imaging system has been developed for ground based studies of the optical signatures of equatorial plasma depletions the system was designed for narrowband interference filters 6 a full width at half power with interchangeable all sky 180 and narrow field 60 lenses and records images photographically by using a standard 35 mm camera a field test of the apparatus was conducted on ascension island 8 0 s 14 4 w from january 24 to february 10 1981 the photographs were analyzed for broad morphological characteristics by using simple overlay techniques augmented by digital image processing methods to extract more quantitative detail the initial results to come from these observations show that airglow depletions occur most often during the 2030 2330 lt period often covering one fourth of the visible sky they extend from the magnetic equator to beyond the crest of the equatorial anomaly with east west cross sections of 100 km to several hundred kilometers they are usually not aligned with magnetic meridians showing a progressive skewness to the west at further distances from the equator several cases of apparently twisting overlapping and bifurcating depletions were observed the depletions drifted to the east with speeds that decreased from 190 m s at 2100 lt to 80 m s at 0100 lt the airglow intensities within depletions were typically 40 50 of the background levels and the western walls of the depletions usually had a steeper gradient than the corresponding eastern walls

high resolution quantitative reconstruction of erosion rates based on anatomical changes in exposed roots at draix alpes de haute provence critical review of existing approaches and independent quality control of results extensive areas of french alps are underlain by jurassic black marls wherever these terres noires crop out they become subject to intense erosion causing major sedimentation in regional reservoirs and river systems in the badlands near draix alpes de haute provence france measured sediment rates were obtained at the plot scale by surface elevation change based methods and at the catchment scale by monitoring sedimentation in dams in this study we use a dendrogeomorphic approach based on anatomical changes in exposed roots of pinus sylvestris l to accurately quantify continuous denudation rates a total of 123 cross sections 75 from buried and 48 from exposed roots of 23 trees were sampled in the moulin basin the size and position of roots at the time of exposure was determined via anatomical variations in the annual growth rings of roots in cross sections of buried roots a sharp reduction of earlywood tracheid lumen area a growth signature which has traditionally been used to determine the moment of root denudation was observed as soon as erosion reduced soil cover to 3 cm as a consequence estimates of eroded soil thickness had to be adjusted to take account of this bias bias adjusted averaged medium term erosion rates derived from exposed roots vary between 6 and 7 mm y 1 at moulin basin depending on the importance accorded to the uplift of roots after exposure values are significantly correlated to slope angle and match with erosion rates derived from monitored iron stakes 5 7 mm y 1 or measurements of sediment yield in retention dams 4 7 mm y 1 at the outlet of the moulin basin besides demonstrating that the interpretation of anatomical signatures in tree roots to erosion have to be revised this paper also shows that dendrogeomorphic analyses of roots are indeed a powerful tool for the quantification of minimal rates of soil erosion in environments where measurements of past activity are not available

mid latitude ionospheric irregularities persisting into late morning during the magnetic storm on 19 march 2001 1 post sunrise intense ionospheric irregularities at low to mid latitudes are reported for the first time a method based on spaced receiver technique is proposed to estimate the apparent drift velocity of the irregularities by using the correlation of the slant total electron content tec from 3 gps receivers the irregularities were detected at 23 45 n by the gps earth observation network geonet of japan from 0455 lt to 1051 lt on 21 march 2001 during the recovery phase of the magnetic storm at the corresponding time spread f was observed with 3 ionosondes located meridionally at okinawa 127 8 e 26 3 n 20 7 n magnetic latitude kokubunji 139 5 e 35 7 n 30 0 n magnetic latitude and wakkanai 141 7 e 45 4 n 40 5 n magnetic latitude while an intense negative ionospheric storm was processing and propagating from mid to lower latitudes the irregularities were seen as plasma bubbles by the defense meteorological satellite program dmsp in situ measurements westward drift with the speed of 100 m s was estimated by spaced receivers from geonet and confirmed by dmsp during the evolution of the irregularities the plasma bubbles at mid latitude sustained 1 5 hour after sunrise and at the lower latitudes they survived more than 4 hours after sunrise the observations suggested that the irregularities were generated by an eastward electric field associated with the disturbance dynamo and the long time existence of the irregularities after sunrise seemed to be related to the daytime intense negative ionospheric storm on 21 march

magnetospheric disturbance induced equatorial plasma bubble development and dynamics a case study in brazilian sector 1 equatorial ionospheric plasma bubble irregularity development and dynamics during the major magnetospheric storm of 26 august 1998 are investigated using the data collected by a multistation and multi instrument diagnostic network operated at equatorial and low latitude sites in brazil and auroral electrojet activity au al imf and dst indices a magnetospheric disturbance onset in the morning of 26 august 1998 was initiated by a solar wind shock and associated imf bz polarity reversals and ssc that were soon followed by a succession of substorm like auroral electrojet ae intensifications and dst development an imf bz southward turning and associated ae intensifications in the brazilian dusk sector produced intense prompt penetration eastward electric field that caused large f region vertical drift and consequently the developments of intense postsunset equatorial anomaly and a series of intense plasma bubbles the latter event lasting the entire night as observed by digital ionosondes at sao luis 2 33 s 315 8 e dip angle 5 and fortaleza 3 9 s 321 55 w dip angle 9 and an all sky imager two scanning photometers and a digisonde at the low latitude site cachoeira paulista 22 6 s 315 e dip angle 28 a notable aspect of the dynamics of the bubbles was their initially very low eastward drift velocity which turned into steadily increasing westward velocity that lasted till early morning hours the results show for the first time a relationship between the zonal drift velocities of optically observed large scale bubbles tens to hundreds of kilometers and that of the smaller scale kilometer sizes structures as observed by a digital ionosonde the results point to the dominant role of a disturbance dynamo associated westward thermospheric wind to maintain the plasma irregularity drift increasingly westward going into postmidnight hours as an important finding the results further show that significant contribution to the westward plasma bubble irregularity drift normally attributed to disturbance dynamo effect could arise from prompt penetration disturbance zonal electric field in the course of a disturbance sequence lasting several hours such effect is attributed to hall electric field arising from the primary disturbance zonal electric field under enhanced nighttime ionospheric conductivities produced possibly by storm associated particle precipitation in the brazilian longitude sector in agreement with recent evidences abdu et al 1998b

experimental analysis of progressive failure behavior of rock tunnel with a fault zone using non contact dic technique abstract geological discontinuities govern the strength and deformation of rock mass and play an important role in the stability of geotechnical excavations such as tunnels caverns slopes and mines in this paper the failure mechanism of a tunnel in the vicinity of a fault zone is investigated by physical model tests with dimensions of 3 m 2 4 m 0 4 m in which the non contact digital image correlation dic technique is employed to provide full field displacement measurements results show that the fault zone near the tunnel shoulder has a significant influence on the stability of the surrounding rock in terms of strain localization and failure initiation with the increase of surcharge loading cracks initiate at the two sidewalls following by the initiation of cracks at the left shoulder and the crown cracks propagate to the fault zone eventually leading to asymmetrical collapse the stress loosening zone slz in the surrounding rock after tunnel excavation is significantly influenced by the fault zone near the left shoulder of the tunnel showing the occurrence of stress redistribution it is recommended to implement reinforcement in the rock mass between the tunnel and the fault to improve the stability

time evolution and dynamics of equatorial backscatter plumes 1 growth phase much of our understanding of equatorial spread f phenomena has resulted from vhf radar studies of backscatter plumes i e patterns of backscatter that appear to extend from the bottomside into the topside of the f layer by using altair a fully steerable backscatter radar to map selected plumes repeatedly it was found that the dynamic behavior of plumes can be characterized by a growth and a decay phase the growth phase characteristics described in this paper are found to be generally consistent with equatorial irregularity generation as predicted by the rayleigh taylor and gradient drift instabilities in particular 1 plumes are generated primarily in the local time around f layer sunset 2 plumes develop from local perturbations in plasma density in the bottomside of the f layer 3 plumes develop upward with growth velocities ranging from 125 to 350 m s and 4 backscatter strength increases during upward plume development and decreases when upward plume growth slows or ceases however certain characteristics namely an east west asymmetry in backscatter strength found in the bottomside f layer have been found that suggest key roles played by the eastward neutral wind and by altitude modulation of the bottomside f layer in establishing the initial conditions for plume growth

biodiversity and terrestrial ecology of a mid cretaceous high latitude floodplain alexander island antarctica the biodiversity and terrestrial ecology of the late albian triton point formation fossil bluff group alexander island antarctica is analysed to improve our understanding of polar biomes during the mid cretaceous thermal optimum this formation was deposited on a high latitude 75 s floodplain and consists of two facies associations a lower braided alluvial plain unit and an upper coastal meander belt unit analysis of fossil plants in well exposed palaeosols reveals the existence of spatially complex plant communities braidplains supported patchy low density 91 trees ha stands of podocarp and taxodioid conifers on floodbasin substrates and conifer cycadophyte fern angiosperm thickets in riparian settings coastal meander belts supported medium density 568 trees ha podocarp araucarian conifer forests on mature floodbasin soils and fern angiosperm ginkgo thickets in riparian settings growth ring analysis indicates plants experienced stressful growing conditions on the braidplain characterized by high frequency flood events but more favourable growing conditions on the coastal plain additional vegetation disturbances were caused by arthropod fungal attack frost and wildfire in terms of structure composition ecology and productivity these predominantly evergreen broad leafed conifer forests bear similarities to the extant temperate rainforests of new zealand

effects of solar and geomagnetic activities on the zonal drift of equatorial plasma bubbles equatorial plasma bubbles are mostly generated in the postsunset sector and then move in the zonal direction plasma bubbles can last for several hours and move over hundreds of kilometers even more than 1000 km in this study we use measurements of ion density by the communication navigation outage forecasting system satellite to determine the orbit averaged drift velocity of plasma bubbles the objective of the study is to identify the dependence of the bubble drift on the solar radio flux and geomagnetic activities in total 5463 drift velocities are derived over may 2008 to april 2014 and a statistical analysis is performed the average pattern of the bubble drift is in good agreement with the zonal drift of the equatorial f region plasma the zonal drift velocity of plasma bubbles increases with the solar radio flux however the increase shows different features at different local times geomagnetic activities cause a decrease of the eastward drift velocity of plasma bubbles equivalent to the occurrence of a westward drift through disturbance dynamo process in particular the decrease of the eastward drift velocity appears to become accelerated when the dst index is smaller than 60 nt or kp is larger than 4

influence of a fault system on rock mass response to shaft excavation in soft sedimentary rock horonobe area northern japan abstract this paper focuses on the stress field that produced a fault system in the horonobe area of japan and considers the relationship between the fault system and the rock mass response to shaft excavation in soft sedimentary rocks in this area hydraulic fracturing investigations in boreholes and tectonic plate movements indicate that the major horizontal principal stress is oriented e w however during shaft excavation the greatest convergence in the shaft was oriented nne ssw therefore it is necessary to understand the influence of the fault system on the rock mass response to shaft excavation we performed a fault slip analysis of faults in the shaft wall and reconstructed the paleostress field that produced the fault system the maximum horizontal principal stress was oriented mainly nne ssw and the minimum horizontal principal stress was oriented mainly wnw ese these directions are similar to the directions of maximum and minimum convergence in the shaft respectively the results show that a fault system can affect the rock mass response to shaft excavation in soft rock and it is considered that the rock mass deformation is controlled by the fault system in addition it may be possible to assess and predict the rock mass behavior by focusing on paleostress field that produced the fault system

effect of geomagnetic activity on equatorial radio vhf scintillations and spread f the paper discusses the occurrence of scintillations of ats 3 137 mhz beacons recorded at huancayo on geomagnetically quiet and disturbed days during the years 1969 1976 and compares the results with the corresponding occurrence of range and frequency spread f at huancayo during the equinoctial months and the december solsticial months the geomagnetic activity reduces the equatorial scintillations during premidnight hours but increases their occurrence during the postmidnight hours these features are very similar to the effect of geomagnetic activity on the occurrence of the range type of equatorial spread f rather than on the occurrence of frequency spread which decreases for any hour of the night during geomagnetic active periods during the june solsticial months the occurrence of both scintillations and spread f is very much reduced however both the phenomena are more frequent on disturbed than on quiet days for any of the hours of the night these effects are consistently the same for any of the years within the solar cycle it is suggested that the equatorial radio scintillations at 137 mhz during the nighttime are produced primarily by the occurrence of the range type of spread f the geomagnetic effects are due to the modifications of the equatorial electric field by the geomagnetic disturbance and thereby affect the development of f region irregularities causing scintillations