on the interpretation of the vhf radar echoes from the equatorial lower e region 1 reanalysis of the recent radar observations reported by tsunoda and ecklund 1999 has been made to explain the vhf radar echoes from the collision dominated lower e region 95 km it is shown that the lower e region echoes extending down to 90 km can be explained using the gradient drift instability if the neutral wind is taken into consideration it is also shown that the inclusion of neutral wind in the growth rate of the gradient drift instability is capable of explaining the day to day variability of the occurrence of the irregularities extending to the lower altitudes interpretation is given of the low value of doppler velocities and the unusual velocity reversal observed by the radar at the lower altitudes that is consistent with the existing theory of the equatorial electrojet

state of the art of modelling two phase flow in fractured rock two phase flow in fractured rock is an important phenomenon for a range of practical problems not the least of which is non aqueous phase liquid napl contamination of groundwater although multiphase systems have long been studied in the petroleum field in the hydrogeological field progress has only just reaches the point where models are being developed scale effect is one of the main issues of concern although models presented in this paper have the potential to provide useful predictions they can only be used to investigate a variety of possible scenarios with parameters being specified in the form of distribution of values the calibration and validation of all but the simplest of these models poses a formidable task with great demands on hydrogeologists and geophysicists to provide adequate data

ionospheric annual anomaly new insights to the physical mechanisms the ionospheric annual anomaly or nonseasonal anomaly of the ionosphere is characterized by globally increased ionization in december solstice than in june solstice though this phenomenon was reported several decades ago the causal mechanisms have not been fully understood till today in this paper the f2 layer peak electron density nmf2 data from formosa satellite 3 constellation observing system for meteorology ionosphere and climate radio occultation observations during the low solar activity year 2009 were systematically analyzed to investigate the physical mechanisms responsible for annual anomaly and its local time latitudinal and longitudinal variability it is found that the annual anomaly is primarily dominant at southern hemisphere at all local times with significant enhancements at equatorial ionization anomaly crest latitudes during noon to afternoon hours and at high latitudes during nighttimes the annual anomaly in northern hemisphere occurs with relatively smaller magnitudes and confined only to morning to early afternoon hours 08 14 lt this study brings out the important roles of effective neutral winds due to the geomagnetic field configuration and the offset between geomagnetic equator and subsolar point for the enhanced plasma density in the southern hemisphere during december that majorly contributes to the ionospheric annual anomaly these results provide new insights to the responsible mechanisms behind the ionospheric annual anomaly and its local time latitudinal and longitudinal variation

threshold height h f c for the meridional wind to play a deterministic role in the bottom side equatorial spread f and its dependence on solar activity 1 detailed investigations have been carried out on the occurrence of bottom side equatorial spread f esf and the thermospheric meridional wind characteristics just before the former s initiation using ground based ionospheric data corresponding to the equinoctial periods of 1993 1998 from trivandrum 8 5 n 76 5 e dip 0 5 n and sriharikota 13 7 n 80 2 e dip 10 n in the indian longitudes critical analysis of the base height of the f region h f at the time of triggering of esf and the polarity of the meridional winds revealed that if the h f is above a certain level esf occurred under both equatorward and poleward wind conditions below that level esf occurred only when equatorward winds were present implying that the equatorward winds must somehow be able to offset the reduced growth rate of the plasma instability responsible for esf a plausible explanation linking equatorial ionization anomaly eia and the consequent equatorial temperature and wind anomaly etwa and the consequent neutral dynamics effectively enabling the instability even at lower height has been offered the threshold height h f c gleaned out on the basis of the polarity of the meridional winds has been shown to bear a linear relation to the solar activity and sheds light on the enigmatic short and long term variability of esf

transient pulse test and morphological analysis of single rock fractures abstract transient pulse tests were performed on single rock fractures at different confining pressures a new data analysis method based on polynomial fitting was introduced to investigate the relationship between flow velocity and hydraulic gradient 3d laser scanning was used to quantify the morphological changes of the fracture surface after the transient pulse test or under the hydro mechanical coupling effect the results show that the flow velocity versus hydraulic gradient data gradient shows a nonlinear relationship at very low hydraulic possibly due to strong solid water interaction but becomes approximately linear after the hydraulic gradient is high enough the permeability of a single fracture is sensitive to the confining pressure as the confining pressure increases the permeability first remarkably decreases when the confining pressure is lower than a certain value and then decreases at a much lower speed when the confining pressure is higher than that value both mechanical and hydraulic apertures decrease at a decreasing rate with the increase in confining pressure the effect of fracture roughness on the permeability is related to the magnitude of the confining pressure rougher fractures have lower permeability at low confining pressures but the opposite can be true when the confining pressure is high enough roughness is no longer critical to permeability when the confining pressure is over a certain value

equatorial spread f instability conditions as determined from ionograms conditions of plasma irregularity or spread f generation under the rayleigh taylor mechanism in the nighttime equatorial ionosphere are examined from ionogram data registered over fortaleza 4 s 38 w mag dip lat 1 7 brazil for a one year period the results show that local ionospheric conditions such as the bottomside f region electron density scale length and the ion neutral collision frequency at the base of the layer at sunset hours determine the generation of the spread f irregularities over the equator in the post sunset hours

an additional layer in the low latitude ionosphere in indian longitudes total electron content observations and modeling 1 the paper presents the observations and modeling of an additional layer in the low latitude ionosphere in indian longitudes the signatures of the additional layer are observed as ledges or humps between the equatorial ionization anomaly trough and crest eia in the latitudinal profiles of total electron content tec measured using a single ground based beacon receiver located at trivandrum 8 5 n 77 e dip 0 5 n in india the ground based ionograms also show the presence of the so called f 3 layer for a short duration corresponding to these signatures and the layer is found to drift upward to the topside ionosphere the study provides first observational evidence that the so called humps in the latitudinal variation of tec are nothing but the upward propagating f 3 layer this conclusion is supported by theoretical modeling using the sheffield university plasmasphere ionosphere model it is shown that upward exb drift and strong equatorward neutral wind perturbed by atmospheric waves can produce the humps in the latitudinal variation of tec through the reduction in the downward diffusion of ionization along geomagnetic field lines the model results also show that the f 3 layer drifts to the topside and forms topside ledges

fission track analysis of uranium distribution in granitic rocks abstract the natural uranium concentration and distribution in three granitoids from australia has been used to develop an understanding of the geochemical processes which control its behaviour in the natural environment and the potential behaviour of some analogue elements within a crystalline high level radioactive waste hlw repository environment in the coles bay granite olympic dam granite and the kambalda granodiorite fission track micromapping has been used to identify primary and secondary distribution between four main mineralogical locales 1 background u 2 resistate u 3 secondary u and 4 fracture u minor concentrations of total u are present as background u in the major rock forming minerals whereas resistate u contributed by the accessory minerals comprises up to 60 of total u two modes of redistribution of primary u are evident 1 in the secondary minerals particularly fe and ti hydroxides and 2 on alteration minerals which infill microfractures the association of u with these secondary and fracture infilling minerals indicates that it has been redistributed during post magmatic hydrothermal alteration and possibly by recent groundwater rock interaction the most important geochemical processes involved in this u redistribution include mobilisation and fixation through complex decoupling and redox reactions and retention by secondary minerals through adsorption and ionic exchange the effect of these processes upon natural u redistribution may be considered as an analogue of geochemical processes around a hlw repository this work shows that a degree of post magmatic alteration of a granite increases the proportion of secondary minerals of high sorption capacity present which may thus enhance the radionuclide retardation capability of the granitoids

rapid highly structured meridional winds and their modulation by non migrating tides measurements from the streak mission 1 measurements of the earth s low latitude thermosphere returned by the ionization gauge on the streak mission are reported and discussed the measurements are of the amount of gas rammed into the sensor by its passage through the thermospheric medium they were obtained in the dusk sector in the altitude range 130 330 km and are shown to be strongly structured by the geomagnetic field similarities to the structure of the equatorial ionization anomaly are discussed the structure is interpreted as being due to rapid several hundred meters per second meridional winds having an antisymmetric pattern with respect to the geomagnetic equator the measurements are interpreted in light of results from other missions and are shown to fit well with ideas based on complementary measurements from the dynamics explorer 2 mission discussed as the equatorial temperature and wind anomaly several features of these winds are described and discussed including their altitude dependence how they form convection cells that extend to high latitude and how the wind amplitudes vary with geographic longitude with an apparent wavenumber one variation the latter characteristic is shown to be consistent with being the signature of tidal variations observed by others approximate calculations utilizing published values for the pertinent parameters are used to show that heating from the dissipation due to ion drag within the ionospheric f region is a dominant driver of the inferred winds

on the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions the equatorial mass anomaly ema in the thermosphere and equatorial ionization anomaly eia in the ionosphere are two interesting phenomena in low equatorial latitude regions previous studies have shown that the ema appears between 1000 and 2000 local time lt and its location of trough is aligned with dip equator indicating the plausible role of the eia structure in the development of ema in this report we conducted a statistical study of the occurrence of postmidnight ema and eia on the basis of the champ in situ measurements during 2002 2008 our results revealed that clear ema and eia structures are sometimes visible in the postmidnight sector 0100 0600 lt during geomagnetic quiet periods kp 3 the postmidnight ema is not necessarily accompanied by the eia signature in both case study and statistics sense being distinct from the daytime situation in addition the occurrence rates of postmidnight ema and eia display contrasting behavior with respect to their local time longitudinal and solar activity dependences the highest occurrence rate for ema is 8 at around 0300 lt while the occurrence rate of the eia decreases gradually from about 30 at around 2300 lt to similar to 5 at 0600 lt longitudinal occurrence of postmidnight eia presents a wave like pattern however no salient feature appears for the longitudinal occurrence of ema postmidnight ema is more likely to occur at lower solar activity whereas an opposite trend presents in the eia on the basis of above results our findings imply that a simple eia ema cause effect relationship does not hold in the postmidnight sector

comment on double porosity models for a fissured groundwater reservoir with fracture skin by allen f moench this paper constitutes a commendable effort to summarize and expand the theoretical basis for the analysis of drawdown data for fractured terrane that can be characterized by matrix blocks the method applies porous media theory to fractured rocks by defining saturated hydraulic conductivity of the fracture system as the product of the hydraulic conductivity by the ratio of the total volume of the openings to the bulk volume of the rock block or fracture according to the method described by gringarten 1982 moench 1984 incorporated the effect of a mineralized film skin on the wall of the fractures where the skin has its own separate hydraulic conductivity and its own thickness the geometries of the block are considered in the controlling equation for the fissured network via the control of the geometry on permeability distribution and on boundary conditions in several respects this approach is similar to the standard approach for leaky aquifers when leakage is derived from storage in the confining layer except for the addition of the hydraulic properties and thickness of the mineralized layer on the walls of the fractures by varying the values of the hydraulic properties of the fracture system and the mineralized layer on the walls of the fractures virtually any drawdown curve can be simulated by the theory not surprisingly the drawdown curves produced by the method type curves are similar in shape to standard leaky aquifer curves within the influence of boundaries or with the influence of partial penetration the method could in fact produce curves identical to those of hantush 1960 see lohman 1979 given appropriate geometry and the absence of a skin on the fractures

hydromechanical interactions in a fractured carbonate reservoir inferred from hydraulic and mechanical measurements hydromechanical coupled processes in a shallow fractured carbonate reservoir rock were investigated through field experiments coupled with analytical and numerical analyses the experiments consist of hydraulic loading unloading of a water reservoir in which fluid flow occurs mainly inside a heterogeneous fracture network made up of vertical faults and bedding planes hydromechanical response of the reservoir was measured using six pressure normal displacement sensors located on discontinuities and two surface tiltmeters a dual hydraulic behavior was characterized for low permeability bedding planes well connected to highpermeability faults displacement responses show high variability nonlinear changes sometimes with high frequency oscillations and a large scattering of magnitudes initial normal stiffnesses and effective normal stresses along fault planes were estimated in the field by interpreting pressure normal displacement relations with a nonlinear function between effective normal stress and normal displacement two dimensional discontinuum modeling with transient fluid flow was performed to fit measurements during hydraulic loading tests results show that the hydromechanical behavior of the reservoir is restored if a high stiffness contrast is allocated between low and high permeability discontinuities thus a dual permeability network of discontinuities will likely also be a contrasting stiffness network in which the deformation of major flow conducting discontinuities is significantly influenced by the stiffness of the surrounding less permeable discontinuities

a new geometrical model for non linear fluid flow through rough fractures summary fractures in rock mass are the main flow paths and introduce as a most important attribute in rock mass hydraulic behavior the non linear fluid flow through rock fractures was studied in this paper computational domain of an artificial three dimensional fracture is generated and used for cfd simulations both laminar and turbulent flow simulations were performed for a wide range of flow rates also a new non linear fluid flow formulation was developed on the basis of some geometrical and kinematical assumptions for fracture and fluid flow respectively based on comparison between simulation results and developed formulation a new geometrical model has been proposed for non linear fluid flow through rough fractures which suggests a polynomial expression like forchheimer law to describe the dependence of pressure drop on flow rate finally this model has been evaluated with experimental results of a fracture with different geometries the results show that the predicted pressure drop for turbulent flow simulation was roughly 3 17 more than those for laminar one at the reynolds number of 4 5 89 5 respectively moreover a good accuracy was found between the proposed model and turbulent flow simulation results these findings may prove useful for computational studies of flows through real rock fractures or inclusions in simulators for large scale flow in fractured rocks

intra ordovician deformation in southeast ireland evidence from the geological setting geochemical affinities and u pb zircon age of the croghan kinshelagh granite the croghan kinshelagh alkali granite intrudes a cleaved volcano sedimentary sequenceon the border of counties wicklow and wexford in southeast ireland u pb dating of zircons fromthe granite indicate a mid caradoc emplacement age of 454 1 ma the duncannon group hostrocks form the southwestern end of the avoca volcanic belt a mid ordovician caradoc sequenceof acid and intermediate lavas and volcaniclastics dolerite dykes intrude the granite elsewhere in theregion dolerites are generally associated with volcanic rocks the main dl deformation within theduncannon group rocks is manifest as a steep dl cleavage generally regarded as a product of latecaledonian regional deformation in southeast ireland the croghan kinshelagh granite showsstrong geochemical coherence with subalkaline varieties of the caradoc volcanic rocks relativelyhigh th y nb and ree contents set it apart from any other known granite type in southeastireland together with the geochemical evidence the age determination of 454 ma indicates that thecroghan kinshelagh granite was generated and emplaced during ordovician volcanism in southeastireland volcanism was closely followed by penetrative deformation and emplacement of the granite the intra ordovician deformation may have been a consequence of closure of the iapetus ocean ormore localized events such as accretion on the hanging wall of the subduction zone the age of thecroghan kinshelagh granite provides an important datum for ordovician volcanism and subductionin southeast ireland

evolutionary phases of equatorial spread f including l band scintillations and plumes in the context of gps total electron content variability a case study 1 the evolution of large scale few kilometers medium scale few hundreds of meters and small scale meters size plasma density irregularities in the postsunset equatorial f region in the context of characteristic gps total electron content gtec variations are reported from indian longitudes the ionograms and gtec from a gps receiver installed as a part of the gps aided geo augmentation network gagan project for satellite based navigation are obtained from an equatorial station at trivandrum 8 5 n 76 91 e dip latitude 0 5 n the variations in the gtec with respect to tec are considered to represent the seed perturbations for the plasma instability that results in the equatorial spread f esf irregularities and are treated as a perturbation factor p the vhf radar at gadanki 13 5 n 79 17 e dip latitude 6 4 n provided the small scale structures of esf the background thermospheric conditions that affect the growth of the plasma instability through ion neutral collision frequency in are estimated using the f region base height h f and the representative scale height of the neutral atmosphere and are represented by a growth factor g the present case study reveals a close coupling between the background ionospheric conditions and the baseline perturbations in deciding the evolutionary phases of esf it has been shown that although large scale kilometer scale irregularities are formed without any constraints when the background ionospheric thermospheric conditions are favorable in the presence of fluctuations in gtec consistently the medium scale and small scale irregularities show remarkable similarity with the variations in the product of the perturbation and growth factors

super plasma fountain and equatorial ionization anomaly during penetration electric field 1 relative importance of diffusion electric field and neutral wind on equatorial plasma fountain and equatorial ionization anomaly eia during a strong daytime eastward prompt penetration electric field ppef event are evaluated using the sheffield university plasmasphere ionosphere model and the recorded ppef during the super geomagnetic storm of 9 november 2004 the fountain rapidly develops into a super fountain during the ppef event the super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces or stops the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss the eia crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the ppef event however the crests become stronger than normal only in the presence of an equatorward wind the results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during a daytime eastward ppef event the equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms

climatology of the equatorial thermospheric mass density anomaly 1 the equatorial anomaly is an interesting and important feature of the earth s thermosphere ionosphere coupling in tropical regions it is an anomalous latitudinal distribution found in both the ionized and unionized part of the atmosphere its equinox configuration consists of a minimum near the dip equator flanked by two maxima on both sides the ionospheric side of this anomaly often referred to as the equatorial ionization anomaly eia has long been recognized since the 1930s however its thermospheric counterpart was only to be glimpsed by the dynamic explorer 2 satellite in the 1970s a global picture of it has been rather recently revealed by the champ satellite in 2005 in this paper we complement previous studies by investigating the climatology of the equatorial mass anomaly ema in the thermosphere using 4 years of champ measurements our analysis has revealed strong variation of the ema with season and solar flux level the ema structure is most prominent around equinox with a crest to trough ratio about 1 05 for f10 7 150 near solstices it is asymmetric about the dip equator the density crest attains maximum 1 2 hours earlier and reaches higher values in the summer hemisphere than in the winter hemisphere the density in ema regions varies semiannually with maxima near equinoxes the latitudinal locations of the ema crests undergo a seasonal variation obviously following the movement of the subsolar point the ema structure has also been found to become more pronounced at higher solar flux levels both the location and magnitude of the ema crests closely follow those of the eia in corresponding seasons and solar flux levels hence demonstrating strong plasma neutral interaction furthermore two seasonal asymmetries clearly present in the globally averaged density with the density in march december being 15 20 higher than that in september june

modelling the elastic and hydraulic properties of fractured rocks abstract it is now commonly accepted that the earth s upper crust is permeated by discontinuities such as joints fractures and cracks in addition artificial fractures are usually created in low permeability reservoirs so that petroleum can be produced economically these discontinuties play a significant part in oil production and geothermal exploitation there is therefore great interest in using seismic measurements to characterize the discontinuities in reservoir rocks a model has been developed to relate the effective elastic properties of rocks containing aligned fractures or joints to their hydraulic properties at various pressures the model is considerably different from the earlier hertzian contact models because in addition to the deformation of asperities in contact due to compression the deformation of void surfaces has also been taken into account when evaluating the specific stiffness of fractures numerical results show that indentation of the void surfaces is the major factor affecting the evaluation of joint stiffness indicating that the previous hertzian contact models underestimate joint compliances the theory has been used to model the velocities and permeabilities measured on carefully fractured rock samples at various confining pressures very good fits between the predicted and measured results have been found

matrix diffusion rates in fractured volcanic rocks at the nevada test site evidence for a dominant influence of effective fracture apertures 1 solute matrix diffusion in saturated fractured volcanic rock at the nevada test site was evaluated from field tracer tests conducted at two different locations and from laboratory scale transport experiments using core samples from the two locations the laboratory tests included 15 separate tracer transport experiments conducted in 8 fractured cores 4 from each location and 17 diffusion cell experiments conducted in matrix material adjacent to the fractures all of the experiments featured two nonsorbing tracers with free diffusion coefficients differing by a factor of approximately 3 to allow the effects of diffusion to be distinguished from the effects of advection dispersion and source term tailing in the experiments when considering all the laboratory and field transport experiments collectively the lumped mass transfer parameter that characterizes matrix diffusion rates sec 1 2 where m is the matrix porosity b is the effective fracture half aperture and dm is the matrix diffusion coefficient appears to decrease as time and length scales of observation increase however these decreasing trends largely disappear when the laboratory and field data are considered separately and there is little difference in dm values measured at different timescales in laboratory experiments using the same rocks also the overall variability in m and dm in the laboratory experiments is not large enough to account for the order of magnitude smaller field scale values of compared to lab scale values we conclude that experimentally observed trends of versus time or distance scale in saturated fractured rocks at the nevada test site are dominated by differences in effective fracture apertures in the various experiments with a tendency toward larger apertures in the field experiments these results underscore the importance of acquiring a better understanding of the factors that control effective fracture apertures as a function of distance scale in fractured media if values of from laboratory and field tracer experiments are to be reliably extrapolated to time and distance scales in risk assessment models

on the combined effects of vertical shear and zonal electric field patterns on nonlinear equatorial spread f evolution in order to understand observations of modulated irregularities in a localized region on the bottomside of the equatorial ionosphere without the presence of vertically rising large scale plume events an investigation is carried out by means of a nonlinear numerical simulation model using different background ionospheric conditions the investigation revealed that the development of long wavelength 200 km perturbations can only be confined to the bottomside of the ionosphere in a localized region with the combined effects of shear in the zonal plasma drift and a nighttime westward electric field the variabilities in the occurrence characteristic are shown to depend on the variabilities in the prereversal enhancement in the zonal electric field further the resurgence of a plume event at a later time as seen by the jicamarca radar is explained on the basis of confined preseeded structures subject to a fresh instability source first evidence is presented that a source of fresh instability may actually be a wind and or a temperature disturbance launched hours earlier by a small substorm

impact of the vertical dynamics on the thermosphere at low and middle latitudes gitm simulations in this study the influences of the electric fields at low and middle latitudes on the ionosphere and thermosphere are investigated by using the non hydrostatic global ionosphere and thermosphere model gitm the equatorial ionization anomaly eia and the equatorial thermosphere anomaly eta are well reproduced in the simulation when the electric fields are included the term analysis of the continuity equation of the neutral mass density shows that the daytime upward vertical wind near the geomagnetic equator tends to increase the local neutral mass density at 400 km altitude while the divergence in the meridional wind associated with the meridional ion drag force tends to transport the neutral mass density away from the geomagnetic equator which might contribute to the formation of the eta trough the vertical dynamics is modulated by the vertical forces including ion drag force and pressure gradient force acting on the neutrals and the changing vertical dynamics can also feedback to vertical ion drag and pressure gradient forces particularly near the geomagnetic equator the daytime vertical ion drag force near the geomagnetic equator is generally upward while the daytime vertical pressure gradient force near the geomagnetic equator is reduced at most times after adding in the electric fields at low and middle latitudes meanwhile the sudden introduction of the electric fields at low and middle latitudes induces an acoustic wave

interpreting tracer breakthrough tailing from different forced gradient tracer experiment configurations in fractured bedrock 1 conceptual and mathematical models are presented that explain tracer breakthrough tailing in the absence of significant matrix diffusion model predictions are compared to field results from radially convergent weak dipole and push pull tracer experiments conducted in a saturated crystalline bedrock the models are based upon the assumption that flow is highly channelized that the mass of tracer in a channel is proportional to the cube of the mean channel aperture and the mean transport time in the channel is related to the square of the mean channel aperture these models predict the consistent 2 straight line power law slope observed in breakthrough from radially convergent and weak dipole tracer experiments and the variable straight line power law slope observed in push pull tracer experiments with varying injection volumes the power law breakthrough slope is predicted in the absence of matrix diffusion a comparison of tracer experiments in which the flow field was reversed to those in which it was not indicates that the apparent dispersion in the breakthrough curve is partially reversible we hypothesize that the observed breakthrough tailing is due to a combination of local hydrodynamic dispersion which always increases in the direction of fluid velocity and heterogeneous advection which is partially reversed when the flow field is reversed in spite of our attempt to account for heterogeneous advection using a multipath approach a much smaller estimate of hydrodynamic dispersivity was obtained from push pull experiments than from radially convergent or weak dipole experiments these results suggest that although we can explain breakthrough tailing as an advective phenomenon we cannot ignore the relationship between hydrodynamic dispersion and flow field geometry at this site the design of the tracer experiment can severely impact the estimation of hydrodynamic dispersion and matrix diffusion in highly heterogeneous geologic media

toward a synthesis of equatorial spread f onset and suppression during geomagnetic storms 1 we present initial steps toward unifying our understanding of storm time equatorial spread f esf by searching for the common elements in past case studies and statistical occurrence patterns we show that the development or inhibition of equatorial irregularities during magnetically active periods can be understood using the ae parameterized fejer scherliess model for disturbance vertical drifts versus storm time and local time this model takes into account the different sources of perturbation electric fields magnetospheric and ionospheric dynamos that ultimately drive the equatorial vertical drifts showing prompt and delayed effects in the premidnight sector where both generation and suppression can occur as well as in the postmidnight period where generation dominates the postsunset period exhibits the greatest variability for storm time esf versus longitude and thus we demonstrate the fejer scherliess model s applicability in a test case 6 april 2000 that had an ae pattern compatible with their parameterization scheme the model successfully accounts for the pronounced longitude confinement in the observed postsunset esf patterns finally we move beyond the empirically derived relationships between geomagnetic indices and the occurrence of esf aarons 1991 into a framework of true solar terrestrial parameters that drive such effects additional case studies taken from the published literature are then used to show a consistent linkage between postsunset esf onset and the interplanetary electric field ief esw while ae dst kp and dst dt indices were used in earlier studies to determine the dusk longitude sector of disturbance electric fields here we attribute to the ief the main role in the determination of this longitude sector

characteristics of intense space weather events as observed from a low latitude station during solar minimum 1 using a dual frequency high resolution software based gps receiver tec and phase have been monitored from calcutta india situated near the northern crest of the equatorial ionization anomaly for studying some space weather events during 2008 2010 data from a dual frequency ionospheric tec and scintillation monitor operational at this station under the international scinda program of the u s air force have also been used this paper presents two cases of intense space weather events occurring in the equatorial latitudes under magnetically quiet conditions during the abnormally prolonged minimum of solar cycle 24 high values of s4 with maximum 0 8 were noted on gps links located almost due south of calcutta 22 58 n 88 38 e geographic magnetic dip 32 n when the look angles of the satellites are more or less aligned with the axis of the anisotropic field aligned irregularities over the magnetic equator associated bite outs in tec of amplitude 40 units were recorded in the local post sunset hours well defined patches of phase scintillations and associated cycle slips were identified on these days higher values of ambient ionization were noted and the diurnal maximum of the electrojet strength was found to be delayed followed by a significant rise of the f region with a high upward drift velocity over the magnetic equator around sunset indicated by ionosonde measurements of in situ ion density using leo dmsp corroborate the f region height rise presence of irregularities in ionization density distributions around 450km was found from c nofs measurements

on the generation and growth of equatorial backscatter plumes 1 wave structure in the bottomside f layer we examine the initial conditions that lead to backscatter plume development in the equatorial f region ionosphere by analyzing altair radar data we obtained the following principal results 1 prior to plume development an altitude modulation of electron density contours exists in the bottomside f layer these quasi periodic variations were mapped spatially over a 1200 km east west distance by using incoherent scatter measurements and found to consist of three cycles with an average spatial wavelength of 400 km 2 the wave structure observed in the bottomside electron density contours grew in amplitude at a rate consistent with that predicted by the generalized gradient drift instability 3 bottomside backscatter developed on the west walls of all three altitude modulated regions followed by plume development from near the crests of these regions

a study on ionospheric scintillation near the eia crest in relation to equatorial electrodynamics equatorial electrojet eej data which are considered as a proxy index of equatorial electric field are analyzed in conjunction with equatorial ionosonde total electron content tec and scintillation data near the equatorial ionization anomaly eia crest for the equinoctial months of high solar activity years 2011 2012 to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern eia crest only geomagnetically quiet and normal electrojet days are considered the diurnal profiles of eej on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks a series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of eej latitudinal profile of tec exhibits resurgence in eia structure around the postsunset period diurnal tec profile near the eia crest resembles postsunset secondary enhancement on the days with afternoon enhancement in eej occurrence of equatorial spread f and postsunset scintillation near the eia crest seems to follow the secondary enhancement events in eej both the magnitude and duration of enhanced eej are found to be important for postsunset intensification of eia structure and subsequent occurrence of equatorial irregularities a critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the eia crest the results are validated using archived data for the years 1989 1990 and explained in terms of modulation effects of enhanced equatorial fountain

neutral temperature anomaly in the equatorial thermosphere a source of vertical winds data obtained from the wats wind and temperature spectrometer instrument on de 2 dynamics explorer during high solar activity show new evidence for the presence of vertical winds of a significant magnitude in the equatorial thermosphere they reveal a latitudinal structure that can be related to the recently discovered phenomena of the equatorial temperature and wind anomaly etwa in the local evening hours the vertical winds usually are downward around the dip equator and collocated with the temperature minimum of etwa in general they are upward at about 24 dip latitude away from the dip equator and are collocated with the etwa temperature crests the magnitude of the vertical winds is in the 10 40 m s range it is proposed that the temperature and pressure ridges formed by the excess ion drag on the zonal winds around the two crests and ordered by the relatively lower ion drag at the trough of the well known equatorial ionization anomaly eia drive a new wind system in the meridional plane and that the measured vertical winds form part of this wind system

evidence for orographic wave heating in the equatorial thermosphere at solar maximum fabry perot interferometer observations of equatorial 630 nm airglow thermospheric winds and temperatures were made at arequipa peru 16 5 s 71 5 w during the solar maximum years of 1989 and 1990 examination of the thermospheric winds measured from doppler shifts of the 630 nm airglow emission in the two directions east and west of arequipa shows that the zonal wind is often significantly weaker over the andes east than over the pacific west in winter between 19 lt and 24 lt the typical reductions in speed found were 40 to 70 m s in the same time period the temperature results show elevated values of 200 500 k for the three directions north east and zenith over mountainous terrain compared with those of the two directions west and south over water this effect fades near equinoctial periods examination of the standard deviation of the temperature ohservations for the five directions showed an increase in this value above the measurement error hy a factor of three for the direction toward the andes east but not for the direction over water south this elevation is consistent with wave activity as a source of the heating viscous dissipation of waves propagating into the thermosphere region from below is suggested as an explanation for the localized regions of heating

variation in aperture estimate ratios from hydraulic and tracer tests in a single fracture previous theoretical discussion of flow and transport in a single fracture has led to a difference of opinion as to whether the aperture estimated from a tracer test need always be less than or greater than the aperture estimated from a concurrent hydraulic test interpretation of previously published field results has to our knowledge not provided a defensible example where the ratio of these two aperture estimates has varied from less than 1 0 to greater than 1 0 in the same fracture using the same analysis techniques in the present paper field experiments involving concurrent hydraulic and tracer tests have been run in two different directions within an isolated fracture aperture estimates were derived from both the hydraulic and tracer tests the ratio of the aperture estimated from the tracer test to the aperture estimated from the hydraulic test is shown to be greater than 1 0 in the first experiment and less than 1 0 in the second experiment despite noise in the hydraulic test of the first experiment it is argued that our interpretation is reasonable as such this represents the first set of experimental results known to us in which a defensible interpretation leads to the conclusion that the aperture ratio varies from greater than 1 0 to less than 1 0 within the same fracture

fracture network characterization using 1d and 2d data of the moragy granite body southern hungary abstract a disposal system for low and medium level nuclear waste in hungary is being constructed inside the fractured rock body of the lower carboniferous moragy granite previous studies proved that the granitoid massif is rather heterogeneous in terms of lithological composition brittle structure and hydrodynamic behaviour a significant part of the body consists of monzogranite while other portions are more mafic in composition and are monzonites as a result of at least three significant brittle deformation events the area is at present crosscut by wide shear zones that separate intensively fractured zones and poorly deformed domains among them due to late mineralization processes some of these fractured zones are totally sealed and cannot conduct fluids while others are excellent migration pathways the spatial distribution of these two types nevertheless does not show any systematics hydrodynamic behaviour clearly reflects this heterogeneous picture in some places hydraulic jumps as great as 25 m at compartment boundaries can be detected in this study the fracture network of the moragy granite body is evaluated from a geometric aspect using datasets measured at a wide range of scales 2d digitized images of a hand specimen one large 20 60 m and 12 smaller subvertical wall rocks outcrops and 120 images from tunnel faces representing the ground level of the underground repository site were analysed moreover 1d data from 13 wells that all penetrate the granitoid massif were studied based on measured geometric data spatial position length orientation and aperture fracture networks are simulated to study connectivity relations and for computing the fractured porosity and permeability at different scales the results prove the scale invariant geometry of the fracture system geostatistical calculations indicate that measurable fracture geometry parameters behave as regionalized variables and so can be extended spatially estimated localities of connected subsystems fit very well with fault zones mapped previously moreover the spatial position of regimes of different hydrodynamic behaviours can be explained by connectivity relations both regionally and within wells

assessing the validity of the channel model of fracture aperture under field conditions in recent investigations of fluid and solute movement in discrete fractures spatial heterogeneity of the fracture aperture has been conceptualized as a series of noninterconnecting constant aperture flow paths or channels two methods of estimating the distribution of the aperture sizes are presented using information from a single hole pumping test and a radially converging tracer test the first method uses the transmissivity of the fracture and mean arrival time of the tracer while the second method uses the mean and variance of the solute arrival time if the fracture can be conceptualized as a series of nonintersecting flow paths of constant aperture the two methods should yield identical estimates for the parameters of the distribution the validity of the channel model can be assessed by comparing the parameters of the distribution that are estimated by the two methods this technique was demonstrated using hydraulic and tracer tests conducted in a discrete areally extensive horizontal fracture in the silurian dolomite in the northeastern illinois a lognormal and a truncated gamma distribution were used to describe the distribution of constant aperture flow paths the lognormal distribution could not reproduce the abrupt rising limb and maximum rate of mass arrival that characterized the tracer tests the gamma distribution more accurately predicted the shape of the breakthrough curves however the two methods of estimating the parameters of the distribution provided significantly different estimates of the variances of the aperture sizes the mean aperture as estimated by the two methods was similar the difference in the variance of the aperture as estimated by the two methods indicates that alternative conceptual models of aperture heterogeneity are required to more accurately describe both fluid and solute movement in this field situation

effect of tortuosity on the stress dependent permeability of tight sandstones analytical modelling and experimentation abstract accurately modelling stress dependent permeability is of great significance to predicting the oil gas production of unconventional tight sandstone reservoirs with time dependent pressure depletion the classic theory indicates that the porosity exponents of the capillary tube model and the fracture model are 2 and 3 respectively however experimental results demonstrate that the value of the porosity exponent usually varies greatly the effect of the nonuniform distribution of tortuosity on stress dependent permeability is rarely studied assuming that tight sandstones with natural microfractures can be represented by a bundle of tortuous capillary tubes and parallel plate fractures a new stress dependent permeability model of tight sandstones is proposed based on fractal theory considering the tortuosity effect the research results show that the porosity exponents of the tortuous capillary tube model and the tortuous plate fracture model are 3 d t 2 and 2 d t respectively here d t is the tortuosity fractal dimension for the capillary tube model and the plate fracture model without tortuosity d t 1 their porosity exponents can be simplified to 2 and 3 respectively the tortuosity fractal dimension is one of the reasons causing the porosity exponent to deviate from the classic theoretical value the newly developed stress dependent permeability model is verified with experimental data determined using tight sandstone core samples from the yanchang formation in the ordos basin china the average error of the permeability prediction under different effective stresses is only 3 78 thus the newly developed model can accurately predict the stress dependent permeability of tight sandstones

modeling gas water processes in fractures with fracture flow properties obtained through upscaling 1 many environmental systems are driven by complex gas water processes in fractured aquifers one example is degassing processes occurring in fractures in the vicinity of radioactive waste disposal sites these fractures can represent a potential fast track for radioactive substances to reach the surface due to buoyancy effects the created gas phase can move relatively quickly to the surface the aim of this paper is to investigate and model the involved processes first a model for a single fracture is developed based on statistical properties of real fractures an aperture distribution raster element model is created a percolation renormalization model yields effective properties such as relative permeabilities and capillary pressure and provides the size of a representative elementary volume these effective relationships represent the basis for modeling the migration of the created gas phase through the fractured aquifer of the subsurface an example modeling degassing and flow in a single fracture is shown and compared to experimental data the presented model represents a conceptual method for degassing processes and the subsequent migration of the gas phase in fracture matrix systems improving predictions on the fate of radioactive substances

nonwetting phase retention and mobilization in rock fractures perchloroethylene pce was injected into fractured limestone samples approximately 0 3 m 0 3 m square under controlled conditions to assess nonwetting phase fracture retention capacity testing was performed using two rock samples containing a single fracture in each one fractured along a bedding plane and the other fractured along a prominent stylolitic joint residual pce saturation decreased from 21 of the fracture volume at horizontal to 3 at completely vertical in the bedding plane fracture and decreased from 27 to 10 of the fracture volume under the same conditions in the stylolitic fracture a portion of the retained residual was removed by waterflooding the fractures the pce retention capacity of both fractures exhibited a strong correlation with combined capillary and bond number nc krwnb provided that initial residual saturation was defined in the absence of both buoyant and viscous forces residual pce saturation decreased as the magnitude of nc krwnb increased however even at nc krwnb values approaching 10 2 all residual pce was not completely removed from the fractures

a physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 1 a physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi instrument observations theoretical modeling and basic principles according to the mechanism an equatorward neutral wind is required to produce positive ionospheric storms the mechanical effects of the wind 1 reduce or stop the downward diffusion of plasma along the geomagnetic field lines 2 raise the ionosphere to high altitudes of reduced chemical loss and hence 3 accumulate the plasma at altitudes near and above the ionospheric peak centered at around 30 magnetic latitudes daytime eastward prompt penetration electric field ppef if it occurs also shifts the equatorial ionization anomaly crests to higher than normal latitudes up to approximately 30 latitudes the positive ionospheric storms are most likely in the longitudes where the onset of the geomagnetic storms falls in the ionization production dominated morning noon local time sector when the plasma accumulation due to the mechanical effects of the wind largely exceeds the plasma loss due to the chemical effect of the wind the mechanism agrees with the multi instrument observations made during the supergeomagnetic storm of 7 8 november 2004 with 18 h long initial phase ip and 10 h long main phase mp the observations which are mainly in the japanese australian longitudes where the mp onset was in the morning 0600 lt 2100 ut show 1 strong positive ionospheric storms in ne nmax hmax global positioning system total electron content gps tec and 630 nm airglow intensity in both northern and southern hemispheres started at the morning 0600 lt mp onset and lasted for a day 2 repeated occurrence of strong eastward ppef events penetrated after the mp onset and superposed with westward electric field started before the mp onset and 3 storm time equatorward neutral winds inferred from 1 and 2 repeated occurrence of an unusually strong f3 layer with large density depletions around the equator was also observed during the morning noon mp

source or sink an assessment of the role of the old red sandstone in the genesis of the irish zn pb deposits the zn pb ba deposits of central ireland are hosted by lower carboniferous waulsortian limestone and navan group carbonate sediments the deposits are located near the margins of subbasins in close association with extensional faults the source of metals and the flow pathways utilized by the hydrothermal fluids responsible for ore genesis have long been a matter of conjecture the devonian to lower carboniferous old red sandstone has been suggested as a possible regional aquifer and metals source therefore a petrographic and lead isotope study of this unit was conducted to assess its putative role in ore formation hydrothermally unaltered old red sandstone has 206pb 204pb 207pb 204pb and 208pb 204pb ratios ranging from 18 71 to 22 45 15 52 to 15 86 and 38 57 to 42 71 respectively the sedimentological characteristics of the red beds coupled with results of isotopic modeling support the conclusion that the lead isotope signature of the unit is predominantly controlled by radiogenic caledonian granite detritus that has an avalonian like character the modeled lead isotope composition of the old red sandstone at the time of the lower carboniferous ore forming event is too radiogenic for it to have acted as the main source of lead for the irish ore field examination of drill core outcrop and underground exposures reveals that hydrothermal alteration within the old red sandstone forms a halo around faults indicating that fluid flow in the unit was predominantly structurally focused these hydrothermally altered sediments have 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 18 21 to 21 77 15 54 to 15 91 and 38 02 to 41 57 respectively unlike the unaltered sediments several altered samples have lead isotope compositions similar to galena from the lower carboniferous deposits petrographic examination reveals that these samples contain trace hydrothermal sulfides that are probably responsible for the orelike signature therefore it appears that at least locally the old red sandstone functioned as a sink for lead during the lower carboniferous mineralizing event the conclusions from this study eliminate the old red sandstone as the main source of lead in the ore field and suggest that deposit lead is derived primarily from lower paleozoic rocks precambrian crystalline basement in view of these results regional gravity driven fluid flow models calling upon an old red sandstone focused flow regime and metals source can be discounted rather deep circulation of fluids through the fractured basement underlying central ireland plays an integral role in the evolution of the ore forming system

deterministic prediction of post sunset esf based on the strength and asymmetry of eia from ground based tec measurements preliminary results 1 this paper provides the first observations of eia asymmetry by receiving beacon transmissions onboard low earth orbiting satellites from a single station ground based receiver the eia strength and asymmetry are derived from the latitudinal profiles of tec obtained from a radio beacon receiver at trivandrum 8 5 n 77 e diplat 0 5 n these two parameters obtained well ahead of the onset time ol esf are shown to have a definite role on the subsequent esf activity in the present paper both these factors are combined to define a new threshold parameter for the generation ol esf it has been shown that this parameter can define the state of the background ionosphere conducive for the generation of esf irregularities much prior to its onset

the geochemistry of the blackstairs unit of the leinster granite ireland the blackstairs unit is the southernmost of the five units which comprise the leinster granite four granite types are recognized which in order of decreasing age are graiguenamanagh granite porphyritic microcline granite non porphyritic granite and type 1 granite using whole rock geochemical data in conjunction with field and petrographic evidence a model is proposed whereby partial melting of a lower palaeozoic immature sedimentary source produced a parental granitic melt which crystallized without further differentiation to form the non porphyritic granites of the northeastern end of the pluton at the sw end this parental melt fractionated to form the porphyritic microcline granite leaving the melt depleted in k 2 o which then crystallized to form a slightly more acidic non porphyritic granite than that at the ne end a mixture of restite minerals plus melt from this partial melting process crystallized forming the graiguenamanagh granite fractionation of thorium into restite allanite in the graiguenamanagh granite accounts for the low th and th u levels which characterize the non porphyritic granite and the leinster granite in general a high degree of partial melting of similar source material produced the low volume type 1 granite magmas which were subsequently intruded along faults a similar petrogenesis is envisaged for the whole of the leinster granite

laboratory measurement of two phase flow parameters in rock joints based on high pressure triaxial testing the accurate flow measurement of each individual phase is important in unsaturated flow through rock joints where both air and water phases flow together an increase in the quantity of one fluid phase decreases the relative permeability of the other phase the relative permeability is important in numerical models to analyze the risk of ground water inundation and uncontrollable gas flows in underground excavations in jointed rock a new apparatus the high pressure two phase triaxial apparatus hptpta has been designed for examining the strength and coefficient of permeability characteristics of fractured and intact rocks under two phase flows in single phase triaxial equipment the rock specimen is subjected to a single fluid flow either water oil or gas through the fractures in the hptpta two fluids e g water 1 air water 1 oil and oil 1 air can be forced to flow through the specimen and the flow rates of the fluids can be measured independently the scope of tests that can be carried out in this apparatus is wide including the evaluation of 1 stress strain behavior subject to internal fluid flow 2 relative permeability of each fluid phase under different degrees of saturation and 3 the associated volume change of the specimen in this paper the design concepts of the hptpta and the results based on the testing of fractured rock specimens are discussed the laboratory results are compared to a simplified mathematical model developed by the writers based on the laboratory results it is shown that the well known darcy s law can be modified for estimating the two phase flow rates using the relative permeability concept

role of equatorial ionization anomaly in the initiation of equatorial spread f a comparative study is made of the changes in the latitudinal structure of the f region electron density at fixed altitudes in the indian equatorial region on days with and without postsunset onset of equatorial spread f using n h profile data of ahmedabad dip latitude 18 6 n waltair dip latitude 10 6 n and kodaikanal dip latitude 1 5 n it is found that on spread f days the ratio of the electron density in the altitude region 270 300 km between ahmedabad and waltair showed a sudden enhancement starting at 1700 lt by a factor of 8 to 30 at 1900 lt from a near constant value of about 2 during the daytime no such enhancement of the density ratio was evidenced on days without spread f the enhancement of the electron density ratio prior to the onset of spread f is interpreted as an intensification of the northern crest of the equatorial anomaly with the ionization in the bottomside f region as far north as 9 from the dip equator participating in the crest intensification process the rapid intensification of the ionization anomaly engenders a similar augmentation of the neutral anomaly around sunset hours this in turn creates a localized cell of altitude dependent equatorward neutral wind that aids further intensification of the crests of both the anomalies and augmentation of ionization in the magnetic field line tube passing through the height of maximum plasma density of the f2 layer over the equator the net result of these coupling processes is a weakening of the ambient transequatorial wind particularly during northern winter months and reduction of the north south asymmetry of the ionization anomaly crests a condition favorable for the onset of spread f maruyama and matuura 1984 the present study thus indicates a significant role of the anomaly intensification at altitudes much below the f region peak and associated neutral dynamics in the initiation of spread f

latitudinal variations of middle thermosphere observations and modeling 1 ching and carter 1974 reported an equatorial bugle of midnight mass density at about 230 km on the basis of ion gauge measurements in april 1972 however since then few succeeding studies of the variation of equatorial mass density in this region have been pursued in this report observations from the satellite electrostatic triaxial accelerometer seta satellite during 1 september 1983 to 31 october 1983 are used to examine the variations of the equatorial density at around 210 km for the daytime 1030 lt and nighttime 2230 lt sectors it is found that mass densities show an equatorial trough around the geographic equator and two crests aside the trough during both daytime and nighttime the thermosphere ionosphere mesosphere electrodynamics general circulation model timegcm reproduces the features seen in the seta data our simulation reveals that the observed double hump structures in both daytime and nighttime sectors are mainly associated with the tides excited locally in the lower and middle thermosphere region although they are modulated by the tides originating from the lower atmosphere

genesis mineralogy and geochemistry of uranium in the gortdrum stratiform copper deposit ireland the gortdrum cu ag as sb hg u orebody occurs in lower carboniferous strata on the downthrown side of an ene transcurrent fault system in southern county tipperary republic of ireland the deposit comprises a linear discordant zone of brecciated carbonates and country rocks that are altered and mineralised research has indicated anomalous radioelement concentrations associated with the main copper orebody and in particular with the altered breccias within this zone the metal association cu ag as sb hg u is considered unique for irish carboniferous carbonate hosted copper deposits however the low temperature mineral assemblage of early uranium bearing minerals with later sulphide stages is reminiscent of many vein type hydrothermal ore deposits the geochemistry of uranium enriched rocks indicates that the alteration of the basic dykes was a most significant event in the trapping of uranium within the limestones propylitization of the early basic dykes by co2 bearing fluids produced the alteration which led to the development of hematite leucoxene and clay minerals the reducing environments attendant with such mineralogy created a favourable environment for uranium precipitation the reduction of u 6 to u 4 by oxidation of reduced fe in dolomitized brecciated limestone occurred prior to the main sulphide mineral sequences the genesis of uranium in the deposit is linked to radioelement remobilization from uranium bearing heavy minerals in sediments of upper devonian lower carboniferous age the uranium became available to low temperature hydrothermal fluids which carried then deposited the uranium along a transcurrent fault system the source of the heavy minerals is considered to be the leinster granite to the east by which time in the carboniferous unroofing of the main pluton had commenced

longitudinal variability of annual changes in activity of equatorial spread f and plasma bubbles global distribution maps of equatorial spread f esf activity for various annual periods were derived from the topside soundings by the ionosphere sounding satellite b iss b in 1978 1980 the esf activity during the northern winter period reveals maximum enhancement at the atlantic longitudes of large westward geomagnetic declination and during the northern summer at the pacific longitudes of large eastward declination on several orbits passing over the region of the esf activity enhancement abrupt depletions of the electron density or equatorial plasma bubbles were observed at the satellite altitude of about 1100 km it has also been found that the background electron density distributions tend to be symmetric with respect to the magnetic equator in the region of the enhanced esf activity and asymmetric in the region of the suppressed esf activity these observations are taken account of by the influence of a transequatorial thermospheric wind upon the suppression of the rayleigh taylor type plasma instability

fracture distribution along an upper jurassic carbonate ramp ne spain abstract understanding the distribution of natural fractures in sedimentary systems is of high relevance for the exploration and production of fluids in the subsurface this study focuses on a kimmeridgian mixed siliciclastic carbonate ramp system which is part of the jurassic limestones outcropping in the northeastern iberian chain the study area is located north of the ricla village fifty kilometers southwest of zaragoza the outcrop stretches over six kilometers in length it allows for recording detailed fracture patterns and facies variations a gis based software package digifract is used to measure and digitize fractures in vertical outcrops fracture orientation measurements obtained from vertical and horizontal outcrops are used to create a conceptual three dimensional image of the fracture distribution of the mixed ramp system the fracture data are processed by integrating outcrop logs and sample data obtained from thin sections and rock property analysis the continuous facies belts of the shallow low angle ramp system show limited lateral variations the studied sediments are subdivided in four main facies tracts ft s ft 1 bioclastic siltstones ft 2 alternating sandy limestones and marls ft 3 cross bedded and channelled oolitic bioclastic sand and grainstones and ft 4 coralgal float to mudstones with eventites measured fracture orientations of the vertical and horizontal outcrops are identical throughout the entire exposure two main fracture sets are identified the first set set 1 has a n s direction and the second set set 2 has a ne sw direction the lateral homogeneity of the sedimentary system thus facies layer thickness and slope angle can be translated to the observed fracture patterns within one single facies belt fractures tend to behave the same in the proximal middle and distal part of the ramp system however vertical facies variations are an important factor for the measured vertical fracture heterogeneity fine grained mud supported facies correspond to periods of a sea level highstand coarse grained cemented facies on the other hand are related to a sea level lowstand the physical contrast of the sediments caused by sea level fluctuations forces fractures to solely concentrate in the brittle layers fracture density and termination patterns observed on this ramp stand in contrast to fracture geometries observed in flat topped carbonate platforms lateral facies heterogeneity and platform anatomy of flat topped carbonate platforms are key parameters for the eventual fracture distribution for the studied mixed ramp type system the vertical facies variations are key parameter

extreme channelization of fluid and the problem of element mobility during barrovian metamorphism geochemical profiles across chemically altered zones selvages surrounding amphibolite facies quartz kyanite veins were investigated to determine major minor and trace element mass transfer and volume strain due to channelized fluid flow the three profiles are perpendicular to two veins cutting the wepawaug schist connecticut u s a which underwent barrovian style metamorphism during the acadian orogeny selvages are highly aluminous with considerably more kyanite staurolite and garnet and less quartz plagioclase and mica than surrounding wallrocks kyanite crystals increase in size toward veins and reach several centimeters in length within veins mass balance analysis indicates 50 silica loss and 34 volume loss from selvages on average silica transferred locally from selvages to veins accounts for 40 to 80 of the vein silica the remainder must have been precipitated from fluids that flowed through the veins during regional devolatilization fluid flow also transported elements into the rock mass which were concentrated in the selvages gains of fe mn y and hree were due to the growth of selvage garnet fe zn and li were sequestered into staurolite kyanite staurolite and garnet growth resulted in al mass gains destruction of mica particularly muscovite and of plagioclase in the selvages resulted in losses of k na ba pb sn and volatiles and losses of na sr and eu respectively thin na and sr enrichment zones associated with increased modal plagioclase are found along the margins between selvages and less altered wallrock and may represent either chemical self organization produced during diffusive mass transfer and reaction or are relics from a possible earlier period of na enrichment in the selvages simple two dimensional numerical modeling of flow in a fractured porous medium indicates that fluxes vary significantly over short distances 1 m adjacent to veins fluids channelized into the high permeability fracture conduits carry the bulk of the fluid flow mass transfer to and from selvages adjacent to the conduits occurred by some combination of diffusion and flow in contrast areas distal to the conduits are impoverished in fluid and undergo much more limited infiltration as a consequence different workers can come to vastly different conclusions about the magnitude of fluid fluxes and element transfer depending on the part of a fractured outcrop studied this extreme spatial variability due to channelization can largely explain contrasting views that have arisen in the literature regarding the nature and intensity of non volatile element mass transfer during barrovian metamorphism determining average time integrated fluid fluxes and levels of element transport across outcrops remains as important research challenges due to the spatial variability of flow

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

flow through fractures flow through fractures is often idealized as flow between two parallel plates plane poiseuille flow the opening or aperture between parallel plates is unambiguous and its relation to flowrate is well known however fractures in rock have uneven walls and a variable aperture a model for flow in a fracture is proposed wherein the fracture is represented by a set of parallel plate openings with different apertures the model leads to a modified poiseuille equation for flow which includes an aperture frequency distribution for the fracture any arbitrary aperture distribution can be used in order to simplify computation and demonstrate the properties of the model a log normal form of distribution is assumed even when an analytical form of the distribution is assumed two parameters rather than a single value representing aperture size are required to determine flowrate models of aperture change for a fracture undergoing compression fracture walls deforming and extension fracture walls separating are developed which constrain the additional parameter and allow calculation of flowrate as a function of mean aperture the theoretical relationships developed between mean aperture and flowrate can be used to interpret published laboratory data for single fractures

analysis of the hydromechanical behavior of a flat lying fracture during a slug test slug tests dilate and contract fractures in aquifers we developed a coupled hydromechanical analysis of an idealized fracture to evaluate effects of these deformations in fractured crystalline rock aquifers the analysis shows the abrupt increase in pressure at the beginning of a slug test causes a slight opening of a fracture but the fracture continues to open as the pressure falls in the wellbore this happens because the pressure increases over an ever widening area even though it decreases in the wellbore eventually decreasing pressure in the vicinity of the wellbore offsets the spreading pressure and the fracture starts to close ultimately returning to its initial aperture when the pressure equilibrates the displacement in the wellbore when the pressure head is rising is always smaller than when the head is falling and this produces a loop like hysteresis when displacement is plotted as a function of pressure a sensitivity analysis shows the displacement at the wellbore is sensitive to the magnitude and distribution of aquifer properties suggesting that the displacement signal could be combined with pressure measurements to improve the interpretation of slug tests during aquifer characterization

response of the equatorial and low latitude ionosphere in the indian sector to the geomagnetic storms of january 2005 1 the equatorial and low latitude ionospheric response to three moderate geomagnetic storms 17 18 and 22 january during the period from 16 to 23 january 2005 is investigated in the context of development inhibition of the equatorial ionization anomaly eia and the subsequent occurrence nonoccurrence of equatorial spread f esf irregularities on these days the study is carried out using the total electron content tec measured with the gps receivers along the 80 e longitude sector and the f layer bottom height obtained from the ionosonde located over the dip equatorial location of trivandrum 8 5 n 77 e dip latitude 0 5 n in india it is observed that for the storms on days 17 and 22 the development of the anomaly was inhibited probably due to the westward disturbance dynamo electric fields subsequently the post sunset enhancement in the vertical drift of the equatorial f region was also inhibited significantly compared to the quiet day pattern and as anticipated no esf was observed on these days a large vertical drift of the equatorial f region followed by nearly simultaneous onset of weak esf was observed on day 18 the late development of the eia on this day could be due to the eastward prompt penetration electric field associated with the southward turning of the interplanetary magnetic field also strong and distinct f3 layer appeared for a short time in the morning reappeared later in the noon time and then quickly ascended to the topside ionosphere during the main phase of the storm on day 18

injection and thermal breakthrough in fractured geothermal reservoirs lbl 12698 preprint submitted to the journal of geophysical research injection and thermal breakthrough in fractured geothermal reservoirs gudmundur s bodvarsson and chin fu tsang may 1981 two week loan copy this is a library circulating copy which may be borrowed for two weeks for a personal retention copy call tech info division ext 6782 prepared for the u s department of energy under contract w 7405 eng 48

closed form flow model of a damped slug test in a fractured bedrock borehole summary an existing closed form model is modified to describe the damped response of groundwater in a fractured bedrock borehole with variable apertures and dips to a slug test the existing theory which requires single sized horizontal fractures is accurately calibrated by slug test data from three uncased bedrock boreholes in the dedham granite and an observation well screened just below the contact surface with a till drumlin apertures and dips vary however so the ability of the modified theory to accommodate different sizes and inclinations improves upon the physical validity of its predecessor when fracture information accompanies slug test data geophysical logs identify a large number and dip of fractures in the uncased boreholes in the dedham granite in this regard a lognormally distributed horizontal aperture calibration of the slug tests in the uncased boreholes retains the accuracy of the single size model and yields aperture statistics more consistent with literature values the slug test in the screened observation well is accurately calibrated with the modified horizontal theory for discrete two sizes based upon the average fracture spacing found in the uncased boreholes all four results yield comparable compressibility estimates which depend on fracture spacing but not size or dip the calibrated aperture size and calculated fracture porosity and permeability decrease with length of the borehole into the dedham granite the measured dip and aperture for flowing and nonflowing fractures in one of the boreholes accurately calibrates the modified theory the inclusion of dip reduces the calibrated permeability because of the increased ellipsoidal area at the interface of the borehole and the inclined fractures

stochastic analysis of early tracer arrival in a segmented fracture pathway a stochastic model for transport and retention in fractured rock is proposed as an alternative to more elaborate numerical simulations contaminants are transported by advection through a series of n rock fractures the microscopic processes of matrix diffusion and sorption act together to retain contaminants in the host rock the transport pathway is characterized by large scale fluctuations in the advection velocity caused by spatial variability in the fracture attributes along the pathway the moments of the time of arrival of an initial solute pulse are related in a generic way to the joint distribution of fracture aperture and length these moments are controlled primarily by a dimensionless retention parameter that incorporates all the deterministic model parameters and by correlation between fracture length and aperture the results show that a systematic bias in the predicted contaminant transport can be introduced by neglecting spatial variability in fracture attributes the relative contributions of fracture to fracture variability and within fracture variability are also explored the proposed stochastic methodology can be merged with relatively simple numerical simulations to broaden the applicability

characterization and impact on reservoir quality of fractures in the cretaceous qamchuqa formation zagros folded belt abstract reservoir quality in tight fractured carbonate rocks is controlled by the fracture properties the tectonic origin of fractures the relationship of fractures to other sedimentary features within the rockmass and diagenesis in this study fracture analysis porosity and permeability of the qamchuqa formation in the miran west block of the zagros folded belt in kurdistan has been studied this was undertaken using core analysis micro resistivity image logs drill stem tests dst mud logging data repeat formation test rft drilled cutting samples and wireline log data the integrated analysis shows that the qamchuqa formation is characterized by heterogeneous sedimentary and tectonic features the sedimentary features include burial stylolites dissolution seams and some fractures which formed at early stages of burial and diagenesis phase 1 open fractures partially open mineralized fractures veins and tectonic stylolites were formed by later tectonic activity phase 2 the finding of this study highlight that the fracture properties including aperture length frequency and origin play an important role in controlling the reservoir s quality the open fractures and partially open mineralized fractures enhance permeability providing an inter connected fracture network leading to a high fracture permeability that controls fluid flow in this tight carbonate reservoir rock the fracture network had little impact on the volume of hydrocarbon storage which is controlled by the pore matrix in contrast structures including stylolites dissolution seams and veins generally have a negative impact on the reservoir quality by blocking the fluid flow this work emphasizes the importance of understanding the regional geological history and the role of sedimentary and tectonic features when investigating in tight carbonate reservoirs