low latitude zonal and vertical ion drifts seen by de 2 horizontal and vertical ion drift data from the de 2 spacecraft have been used to determine average zonal and vertical plasma flow electric field characteristics in the plus minus 26 degree dip latitude region during a time of high solar activity the data base consists of over 800 equatorial passes horizontal ion drift data were projected along magnetic field lines to the magnetic equator using a dipole model to yield their apex height dependence the average data local time profile for an apex height bin centered at 400 km indicates westward plasma flow from 0600 to 1900 solar local time slt with a maximum westward velocity of 80 m s in the early afternoon there is a sharp change to eastward flow at approximately 1900 hours with an early evening peak of 170 m s a secondary nighttime maximum exists a 0430 slt preceeding the reversal to westward flow this profile is in good agreement with jicamarca radar measurements made under similar solar maximum conditions harmonic analysis indicates a net superrotation which is strongest at lower apex altitudes the diurnal term is dominant but higher order terms through th quatradiurnal are significant vertical ion data taken at low plus minus 5 degree dip latitudes while possessing greatermore scatter generally agree wtih jicamarca values copyright american geophysical union 1989 less

equatorial zonal plasma drifts measured by the c nofs satellite during the 2008 2011 solar minimum 1 we use the measurements by the vector electric field investigation vefi on board the communication navigation outage forecasting system c nofs satellite to study the local time and seasonal and longitudinal dependent climatology of equatorial f region zonal plasma drifts during 2008 2011 these drifts are essentially westward during the day and eastward at night over jicamarca radio observatory the satellite measurements are in good agreement with incoherent scatter radar drifts our data show strong longitudinal variations particularly in the south american sector during the solstices the equinoctial data exhibit short lived and largely enhanced westward drifts near sunrise and wave 4 structures from the early afternoon to late night equinoctial periods the nighttime eastward drifts are largest near the western american sector at all seasons the june solstice postmidnight eastward drifts decrease sharply at longitudes of about 310 and have much smaller values in the entire eastern hemisphere we also briefly discuss the relationship between the longitude dependent vertical and zonal plasma drifts

volumetric flattening an interpretation tool volumetric flattening is a novel method for automatically flattening 3d seismic cubes that converts seismic volumes to volumes of horizon slices with little or no effort an interpreter can scan over the resulting horizon slices to see channels and other geologic features as they were laid down furthermore the flattening transformation captures the shapes of all horizons in the cube this transformation leads naturally to numerous interpretation applications ranging from isopach analysis to stratigraphic attributes this algorithm is currently able to reconstruct across nearly vertical faults and incorporate hard constraints such as manual picks and well ties in summary this data driven method exploits the computer s ability to honor all of the data in all three dimensions to remap the data to a more geologically intuitive format

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

area selection for diamond exploration using deep probing electromagnetic surveying abstract previously proposed methods of area selection for diamond prospective regions have predominantly relied on till geochemistry airborne geophysics and or an appraisal of tectonic setting herein we suggest that a novel deep probing geophysical technique electromagnetic studies using the natural source magnetotelluric mt method can contribute to such an activity essentially diamondiferous regions must have 1 old lithosphere 2 thick lithosphere and 3 lithosphere that contains high concentrations of carbon deep probing mt studies are able to address all three of these the second and the third of these can be accomplished independently using mt but for the first the geometries produced from modelling the mt observations must be interpreted with appropriate interaction with geologists geochemists and other geophysicists examples are given from the slave and superior cratons in north america with a brief mention of an area of the rae craton and general speculations about possible diamondiferous regions

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

seismic evidence for the stratified lithosphere in the south of the north china craton 1 the north china craton ncc formed in the paleoproterozoic and suffered cratonic destruction in the mesozoic it consists of the western ncc wncc the trans north china orogen tnco and the eastern ncc encc we investigated the upper mantle structures in the southern ncc by using receiver functions analysis polarization analysis was applied to increase the quality of receiver functions the seismic images show significant stratified structures in the upper mantle in the south of the ncc in the south of the wncc the lithosphere is 280 km thick and contains a low velocity zone at 110 220 km depth this low velocity zone is interpreted as an intracratonic partial melting zone in the south of the tnco and encc there is a low velocity zone at 60 200 km depth which results from the partial melting during the mesozoic cratonic destruction its upper boundary is interpreted as new lithosphere asthenosphere boundary at 60 100 km depth below this low velocity zone there are the remains of archean lithosphere ral blocks of ral stagnate in the asthenosphere and reach depths over 300 km a high velocity slab extends from the uppermost mantle of the wncc into the ral with a dip angle of 20 this slab is interpreted as the paleoproterozoic slab which indicates an eastward subduction between the wncc and the encc the wncc is stable the lithosphere in the south of the tnco and encc suffered the mesozoic cratonic destruction while the destruction is relatively weaker than that in the north of the encc

domain transform a tool for imaging and interpreting geomorphology and stratigraphy in seismic volumes the presence of complex structure on seismic data often makes it difficult to recognize and interpret depositional systems in the volume a number of techniques under the broad topic of chronostratigraphy have been developed in recent years to address this problem and enable more complete imaging and interpretation of seismic geomorphology and stratigraphy a domain transform dt is an interpretation guided process designed to remove some or all structural deformation from a seismic volume it improves the imaging of paleo depositional systems by creating a volume that consists of approximations of paleo depositional surfaces such volumes are ideal for imaging analysis and interpretation of seismic geomorphology and stratigraphy

comparison of nighttime zonal neutral winds and equatorial plasma bubble drift velocities over brazil 1 we present results from the first extended period of coincident observations of thermospheric zonal neutral winds and equatorial plasma bubble epb zonal drift velocities over northeastern brazil during the october to december months of 2009 and 2010 the epb zonal drift velocities are estimated utilizing images of the o i 630 0 nm emissions recorded by a wide angle imaging system at cajazeiras thermospheric neutral wind estimates are based upon common volume observations made by a bistatic fabry perot interferometer fpi experiment using fpis located at cajazeiras and cariri in brazil observing the doppler shift of the o i 630 0 nm emission the results illustrate a similar pattern of nighttime and night to night variations in the zonal neutral winds and epb zonal drift velocities in general the geomagnetic zonal neutral winds and the epb velocities show an excellent agreement illustrating that the f region dynamo is fully developed however in the early evening hours the epb zonal speed is slower than that of the background winds on several occasions we conclude that this indicates that during the bubble evolution period in the early evening the f region dynamo is not fully activated

east west ion drifts at mid latitudes observed by dynamics explorer 2 zonal ion drifts measured from the polar orbiting de 2 spacecraft are examined to determine the effects of dynamo electric fields and penetration of high latitude electric fields at middle latitudes construction of a local time distribution from satellite data results in a mixture of local time and season as well as a range of magnetic activity encompassing kp le 2 and kp ge 3 thus some combination of magnetospheric effects expected to dominate during disturbed times are seen during both quiet and disturbed times and solar tidal influences are most easily observed during quiet times during quiet times at invariant latitudes near 25 degrees the solar diurnal tide dominates the local time distribution of the ion drift at latitudes above 50 degrees a diurnal component of comparable magnitude is also present but its magnetospheric origin produces a shift in phase of almost 180 degrees from the lower latitude diurnal tide in the intervening region between 20 degrees and 50 degrees invariant latitude semidurnal and terdiurnal components in the local time distribution of the drift velocity are also seen these components are generally larger than those seen by ground based radars during quiet times and may be attributable in part to a difference in solarmore activity and in part to a combination of the solar tides and magnetospheric penetration fields less

dependence of the evening prereversal enhancement of the vertical plasma drift on geophysical parameters 1 the variability of the evening prereversal enhancement pre of the vertical plasma drift has been investigated by using the average velocity at a fixed local time range but this method does not provide a clear distinction between the pre occurrence frequency and magnitude in this study we examine the dependence of the occurrence frequency occurrence local time and magnitude of the pre on geophysical parameters by using the retrievals of the individual pre from the first republic of china satellite data our result shows that the seasonal longitudinal variation of the average vertical velocity in the evening that has been identified in previous studies is associated with both the pre occurrence frequency and pre magnitude the magnitude of the pre shows an increasing trend with an increase of the solar flux and with a decrease of the conjugate e region sunset time lag the seasonal longitudinal variation of the occurrence local time of the peak pre shows a dependence on the e region sunset time at the magnetic equator rather than on the magnetic declination or the sunset time lag in the conjugate e regions this observation indicates that the optimum time for the creation of the peak pre is when the sunset terminator at the e region height and the magnetic meridian intersect near the magnetic equator

building 3d subsurface models conforming to seismic structural and stratigraphic features abstractsubsurface modeling from seismic and borehole data is important for reservoir prediction geophysical exploration and production a reasonable model should honor borehole rock properties and conform to seismic structural and stratigraphic features such a subsurface model can be difficult to build in cases complicated by faults and unconformities automatic and semiautomatic methods have been proposed to build subsurface models from seismic and borehole data however seismic structural and stratigraphic features and borehole measurements are not fully used in most methods i have developed a workflow to fully use seismic and borehole data to build subsurface models that honor borehole measurements and conform to seismic horizons faults unconformities and stratigraphic features such as channels in this workflow i first automatically remove the faulting and folding in seismic and borehole data and map them into an unfaulted and flattened space in which seismic reflectors and borehole measure

equatorial f region vertical plasma drifts seasonal and longitudinal asymmetries in the american sector longitudinal and seasonal asymmetries in the evening ionospheric f region plasma vertical drift v sub z enhancements between two longitudinally separated stations situated along the magnetic equator in the american sector are investigated under solar maximum conditions based on results obtained from the analysis of ionosonde data for these stations the two stations are huancayo peru and fortaleza brazil which have markedly different magnetic declination angles the observed asymmetries are interpreted using a detailed numerical simulation of the e and f region electrodynamic coupling process that takes into account also its asymmetry about the magnetic equator arising from the finite magnetic declination angle the results of the simulation show in agreement with observations that the occurrence time of the evening f region vertical drift prereversal peak and its seasonal variation at a station are controlled by the magnetic declination angle at that station which determines the seasonal variation of the sunset times and hence the integrated pedersen conductivity longitudinal gradient at its magnetic conjugate e layers the amplitude of the prereversal peak on the other hand undergoes the influence of the magnetic declination angle as well as of the thermospheric zonal wind component

superrotation of the ionosphere and quiet time zonal ion drifts at low and middle latitudes observed by republic of china satellite 1 rocsat 1 1 local time variations of zonal drifts at different latitudes longitudes and seasons are investigated using ion drift measurements from the republic of china satellite 1 rocsat 1 we select a quiet time period defined when dst 100 nt and kp 3 the ion drifts in the magnetic zonal direction are latitude apex height dependent and differ for different longitude sectors and seasons superrotation of the ionosphere is observed in the zonal drift measurements particularly at the lower latitudes the ionospheric superrotation generally decreases with increasing latitude and is attributed mainly to the f region dynamo where the features of the neutral wind and conductance affect the characteristics of the superrotation at different latitudes longitudes and seasons we suggest that the latitudinal variation of the superrotation is mainly produced by the decrease in latitude of the neutral winds in the f region a decrease of conductance with increasing latitude is also present but evidence shows that neutral winds decrease faster with latitude than the conductance for high solar flux conditions the longitudinal and seasonal variations of the superrotation are more influenced by changes in the f region conductance that is modified by vertical e b ion drift motions and neutral wind induced ion drift motions along magnetic field lines

equatorial ionospheric zonal drift by monitoring local gps reference networks 1 the propagation of electromagnetic waves through the turbulent ionosphere produces scintillations through diffraction and understanding the physical nature of scintillations is important for engineers and technologists as well as for scientists in recent years the establishment of the global positioning system gps provided a new technique that can be used to study ionospheric scintillations the usual way of doing that is the deployment of gps receivers closely spaced in east west magnetic direction and then estimating the zonal drift velocities based on the signal power observations one of the weaknesses of this method is that high rate sampling such as 20 hz is required for close spaced stations and generally no such data are available for studying ionospheric scintillation in the past years in this research work a scintillation monitoring method based on slant tec stec observations of local gps continuously operating reference station cors network is proposed first the past research works on the equatorial ionospheric drift velocities are summarized then by comparing the scintillation pattern of the signal power and stec observations of california local gps reference network we find that the stec is a good choice for estimating the ionospheric zonal drift velocity then it is illustrated how to calculate the ionospheric scintillation velocity based on stec finally the proposed method is applied to hong kong gps reference network and several cases of the calculated ionospheric zonal velocities are given

longitudinal and seasonal variations of the equatorial ionospheric ion density and eastward drift velocity in the dusk sector 1 the longitudinal and seasonal variations of the plasma density and drift velocity in the evening equatorial ionosphere show complex characteristics in this paper we analyze the ionospheric ion density and velocity measured by the defense meteorological satellites program dmsp f13 and f17 satellites at 1800 lt our analysis focuses on whether the longitudinal structure of the equatorial ionospheric density and velocity has multiple wave number components how the longitudinal structure of the equatorial ion eastward drift varies with season and year and what causes the longitudinal variations of the ion density and velocity we find that the longitudinal structure of the ion density and velocity show a wave 4 pattern during the equinox months march april september and october a wave 3 pattern in northern summer may august and a wave 2 pattern in northern winter november february the longitudinal structure of the ion density and velocity becomes significantly different from the wave 4 pattern in the longitude regions with large magnetic declination in the summer and winter the variation of the equatorial ionospheric ion density shows an in phase correspondence with the ion eastward velocity and an anti phase correspondence with the ion upward velocity we suggest that the enhanced upward drift causes the density decrease through the fountain effect and that the enhanced eastward drift causes the density increase through horizontal transport the change of the ion eastward velocity with longitude can be as high as 180 m s 1 over a longitudinal range of 120 and is related to the solar activity the results of this study reveal a number of new characteristics of the equatorial plasma horizontal drift in the east west direction

stratal slicing benefits and challenges in the petroleum industry seismic interpretation meth odology varies according to a subject s scale in basinal to field scale hundreds of meters the goal is to map gross stratigraphic and structural features that are associated with petroleum systems including stratigraphy and depositional history hydrocarbon generation migration and entrapment seismic stratigraphy and sequence stratigraphy are common tools for this purpose at the reservoir scale meters to tens of meters the goal becomes characterizing distribution and physical properties related to volumetrics and production in a reservoir system in this task details are crucial seismic lithology and inversion seismic geomorphology and sedimentology and attribute analysis are some of the tools developed for this purpose

influences of geomagnetic fields on longitudinal variations of vertical plasma drifts in the presunset equatorial topside ionosphere on the basis of the measurements from the ion drift meter on the defense meteorological satellite program f13 satellite from 2000 to 2002 the relative longitudinal variations of e x b vertical plasma drifts in the presunset equatorial topside ionosphere at 1745 lt are examined obvious influences of geomagnetic fields on longitudinal variations of e x b vertical plasma drifts which also show a seasonal dependence have been found during the june solstice the relative vertical plasma drifts is most significantly influenced by the geomagnetic field declination however the relative vertical plasma drifts during the december solstice more strongly correlates with the geomagnetic field strength although the relative vertical plasma drifts during equinox are also influenced by the geomagnetic field declination an underlying dependence on magnetic field magnitude as seen in december is also present

the earth s thermospheric superrotation from dynamics explorer 2 neutral thermospheric zonal winds measured from the wind and temperature experiment on dynamics explorer 2 have been analyzed to provide a measure of the superrotation of the neutral thermosphere the data were averaged in local time in 10 degree bands from the equator to 40 degrees latitude the results show an average wind velocity on the order of 18 m s to the east at the equator and a westward wind of the same magnitude at mid latitudes within the range of altitudes of the data base 200 to 700 km no evidence of any significant altitude dependence was found averaging our data over the latitude bands studied indicates a net corotation of the thermosphere this result is not in agreement with the superrotation value reported by king hele and walker on the basis of satellite drag analysis

altitudinal dependence of evening equatorial f region vertical plasma drifts we use jicamarca incoherent scatter radar measurements to study for the first time the altitudinal variations of late afternoon and early night equatorial f region vertical plasma drifts we also present the initial vertical drift measurements over the altitudinal range from about 200 to 2000 km these data show that the afternoon drifts decrease weakly with altitude near their evening prereversal enhancements the vertical drifts generally increase with altitude below about the f layer peak decrease with height near the f layer peak and above and are nearly height independent in the solar flux dependent topside ionosphere the transition altitudes from height decreasing to height independent evening upward drifts decrease with altitude from solar maximum to solar minimum after their reversal to downward the vertical drifts do not change much with height the altitudinal dependence of the evening vertical drifts has large day to day variability and is closely related to the time dependence of the zonal drifts as expected from the curl free electric field condition

the wheeler diagram flattening theory and time abstract wheeler diagrams are excellent tools to represent time stratigraphy these diagrams are produced by considering interpreted surfaces as snapshots of geologic times linked with transit cycles of the base level the base level defined in the nineteenth century can be regarded as an ultimate time reference for stratigraphic units the application of the base level concept to deep marine settings is a more recent development even though the same definition applies to all depositional environments flat timelines are also known as flattening theories can produce similar looking diagrams and have an edge that they operate in 3d however flattening of a dataset can be achieved with various techniques which are reviewed and the optimum algorithm which has a future application for hydrocarbon and research communities is improved to honor geological constraints such as faults and horizons a secondary aspect of the wheeler diagrams is the dual nature of geological timelines the diagrams are originally plotted on a relative geological time scale and no formal technique has yet been recommended for time calibration in this paper a nomogram approach is proposed to calibrate the timelines the representation of unconformities that are parallel to bedding planes is another important idea presented in this paper

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

equatorial f region zonal plasma drifts we have examined in detail the f region plasma drifts measured at jicamarca peru during 1978 1981 a period of high solar activity and compared these drifts with jicamarca data taken during periods of lower activity as well as with other equatorial zonal neutral wind and plasma drift measurements the increase in solar activity causes larger nighttime eastward plasma drifts at jicamarca and delays the morning reversal time from eastward nighttime to westward daytime drifts the radar data seem to be in good agreement with nighttime neutral wind measurements made by the de 2 satellite but are systematically smaller than spaced receiver drifts measured with both the scintillation and the vhf polarimeter techniques for integration times of 20 30 min but perhaps not for shorter integrations the jicamarca zonal plasma drifts measured with both the incoherent scatter and the radar interferometer technique change little with altitude near the f region electron density peak and above however at nighttime below the f peak there is a clear shear in the zonal plasma drifts with decreasing eastward drifts below the f peak reversing to westward drifts at lower altitudes the nighttime profiles of the equatorial plasma drifts are in good agreement with the results from recent numerical models of the equatorial ionosphere

equatorial ionospheric vertical plasma drift model over the brazilian region comparison between equatorial inospheric f region vertical plasma drift from satellite measurements fejer et al 1995 for the brazilian longitude sector and the drifts derived from ionosonde measurements around sunset shows significant differences on the prereversal peak behavior during solstices of high solar activity periods using ionosonde measurements around sunset and satellite measurements at other local times we constructed an ionospheric vertical plasma drift model that is representative of the equatorial region over the brazilian longitudes where the magnetic declination is around 20 the so derived drift model here called idm ionosonde drift model is used as an input to the sheffield university plasmasphere ionosphere model supim it is shown that the f layer heights given by supim with idm are in good agreement with ionosonde measurements over the brazilian longitudes and that idm better simulates the f layer heights than the averaged drifts given by the satellite drift model fejer et al 1995

an experimental study of partitioning of fluorine between k richterite apatite phlogopite and melt at 20 kbar phase relations have been determined at 20 kbar and primarily under suprasolidus conditions in the fe ti free f bearing k richterite phlogopite and k richterite apatite systems in order to assess the partitioning of f among phlogopite k richterite apatite and melt under upper mantle conditions both systems are pseudoternary because they contain forsterite enstatite and a diopside rich clinopyroxene from the breakdown of the mica and k richterite the f bearing k richterite systems have lower minimum melting temperatures than the f bearing phlogopite apatite system at the same pressure however in the systems studied f in phlogopite appears the most effective component in altering minimum liquid compositions whereas comparison between the present study and previous systems suggests that the presence of p2o5 during melting may result in more k enriched melts variations in the compositions of the f bearing phases are primarily controlled by the bulk compositions of the end member minerals and by temperature although buffering by non f bearing minerals e g clinopyroxene may be effective distribution coefficients as wt ratios between f bearing minerals and coexisting liquids have been determined as functions of bulk composition and temperature for products of experiments distribution coefficients between k richterite liquid apatite liquid and phlogopite liquid are 1 to slightly 1 for most bulk compositions indicating thatf is generally a compatible element this conclusion is in agreement with the sequence off distribution for similar phases in ultrapotassic rocks these results preclude f bearing mineral reservoirs in the mantle at depths corresponding to 20 kbar being capable of producing f enrichment in ultrapotassic magmas or being effective in redox melting processes

on the height variation of the equatorial f region vertical plasma drifts we have used improved incoherent scatter radar measurements at the jicamarca radio observatory to study the height variation of the f region vertical plasma drift velocity driven by the zonal electric field during moderately quiet conditions preliminary results indicate a nearly linear change of the vertical drift velocity with altitude between 200 and 700 km but with considerable day to day variations in the value of the slope on the average the velocity gradients are positive in the late night and morning periods and negative during the afternoon and evening hours simultaneous vertical and zonal drift measurements confirm that the measured height variation of the vertical drift is consistent with the existence of a curl free electric field in the low latitude ionosphere the time dependence of the jicamarca vertical drifts extrapolated to higher altitudes closely resembles the diurnal variation of the drift component due to the zonal electric field observed at f region heights over arecibo

the prereversal enhancement of the zonal electric field in the equatorial ionosphere the electric fields in the ionospheric e and f regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward normally daytime field reverses to westward several theoretical models of the low latitude fields suggest that this enhancement is caused mainly or entirely by f region winds the f region dynamo but some authors have suggested that it could be produced solely by e region tidal winds we give here additional calculations and arguments in support of the f region source the enhancement of the eastward field for an eastward f region wind turns out to be a simple direct consequence of the fact that after sunset the ionospheric conductivity decreases far more rapidly in the e region than in the f region

chemical and isotopic evidence for major mass transfer between mafic enclaves and felsic magma abstract in both the strontian and criffell zoned granitoid plutons certain chemical elements notably k rb ca sr and pb display a correlation between their concentration in microdiorite enclaves and their concentration in the immediately enclosing host granitic rock this appears to represent the effects of post incorporation mixing and exchange between the enclave and its host magma enclave initial 87 sr 86 sr ratios are indistinguishable from those of the host while enclave initial 143 nd 144 nd ratios are systematically more radiogenic establishing that these enclaves are not melt segregations nor restite the isotopic data are in agreement with the chemical data in indicating that sr is almost entirely derived from the host despite clear evidence of major mass transfer of alkali metals alkali earths and transition metals a comparison of the concentrations and ratios of hfse and ree and nd isotopic ratios with those of a number of potential starting protoliths allows the enclave precursors to be positively discriminated in this regard enclave hfse and ree compositions may allow for models of granitoid production by the injection of hot mantle derived magmas into the crust to be tested

a statistical analysis of equatorial plasma bubble structures based on an all sky airglow imager network in china this paper investigates the statistical features of equatorial plasma bubbles epbs using airglow images from 2012 to 2014 from a ground based network of four imagers in the equatorial region of china it is found that 1 epbs mainly occur during 21 00 00 00 local time lt in equinoxes there is an asymmetry in occurrence rates between march june and september equinoxes december solstices 2 most epbs occur in groups of two to six depletions the distance between adjacent epb depletions is 100 700 km and the average is 200 300 km the zonal extension of an epb group is usually less than 1500 km but can reach 3000 km 3 epbs usually have a maximum drift velocity near 100 m s at 21 00 22 00 lt in 9 5 1 5 geomagnetic latitude and then decrease to 50 70 m s toward sunrise 4 the averaged westward tilt angle of most epbs with respect to the geographic north south increased from 5 10 to 23 30 with lt between 20 00 and 03 00 lt then decreasing to 10 20 toward sunrise 5 when 90 140 the maximum pmle increases by 3 4 5 5 when f10 7 changes from 90 to 190 6 the epb occurrence patterns and zonal drift velocities are significantly different from those at kolhapur india which locates west to our stations by 20 0 32 0 in longitude

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

relative geologic time age volumes relating every seismic sample to a geologically reasonable horizon the age volume described in this paper can significantly increase the amount of useful geologic information extracted from a seismic data volume this paper has three goals the first is to introduce and describe the relative geologic time volume referred to herein as either an rgt volume or an age volume every seismic sample in an age volume contains an estimate of the relative geologic time for that sample which automatically relates every sample to a geologic horizon the second goal is to discuss some of the applications and advantages of using a rgt volume to store and access seismic interpretation for example it can be used to sculpt a seismic volume along a desired horizon or view depositional changes as a function of geologic time the third goal is to describe two methods for generating such a volume the first employing standard interpretation techniques and the second relying on unwrapping instantaneous phase unwrapping the instantaneous phase is a new holistic approach to interpreting seismic data that can produce a very detailed seismic interpretation the goal of building and using an rgt volume is to extract significantly more geologic information from the seismic data than is available from conventional methods the rgt volume is both a way of storing and retrieving seismic horizons to generate such a volume each seismic sample needs to be assigned an estimate of relative geologic time which in essence connects it to a geologically reasonable horizon in normal sections these relative geologic time values will increase with depth or traveltime high gradients in the rgt volume could be indicative of faults unconformities fluid contacts or interpretation errors while a constant value surface in a rgt volume is a seismic horizon figure 1 contains a portion of the seismic data used to illustrate the

radar and satellite global equatorial f region vertical drift model we present the first global empirical model for the quiet time f region equatorial vertical drifts based on combined incoherent scatter radar observations at jicamarca and ion drift meter observations on board the atmospheric explorer e satellite this analytical model based on products of cubic b splines and with nearly conservative electric fields describes the diurnal and seasonal variations of the equatorial vertical drifts for a continuous range of all longitudes and solar flux values our results indicate that during solar minimum the evening prereversal velocity enhancement exhibits only small longitudinal variations during equinox with amplitudes of about 15 20 m s is observed only in the american sector during december solstice with amplitudes of about 5 10 m s and is absent at all longitudes during june solstice the solar minimum evening reversal times are fairly independent of longitude except during december solstice during solar maximum the evening upward vertical drifts and reversal times exhibit large longitudinal variations particularly during the solstices in this case for a solar flux index of 180 the june solstice evening peak drifts maximize in the pacific region with drift amplitudes of up to 35 m s whereas the december solstice velocities maximize in the american sector with comparable magnitudes the equinoctial peak velocities vary between about 35 and 45 m s the morning reversal times and the daytime drifts exhibit only small variations with the phase of the solar cycle the daytime drifts have largest amplitudes between about 0900 and 1100 lt with typical values of 25 30 m s we also show that our model results are in good agreement with other equatorial ground based observations over india brazil and kwajalein

comparison of zonal neutral winds with equatorial plasma bubble and plasma drift velocities 1 a one year dataset spanning march 2011 to march 2012 of coincident observations of nighttime thermospheric zonal neutral winds equatorial plasma bubble epb velocities and zonal plasma drifts is used to examine the relationship between the thermosphere and the ionosphere near the geomagnetic equator over peru thermospheric neutral winds are determined by using a bistatic fabry perot interferometer fpi experiment located at merihill and nazca in peru the ambient plasma drift velocities were obtained using the incoherent scatter radar at the jicamarca radio observatory in peru the epb zonal velocities were estimated utilizing images of the oi 630 0 nm emission recorded by a narrow field optical imaging system at the cerro tololo inter american observatory in chile the joint analysis of these datasets illustrates that the nighttime and night to night variations in the zonal neutral winds epb velocities and plasma drifts are well correlated this consistent result of the local time variations of the neutral winds with that of epb and plasma drifts illustrates that the f region dynamo is in general fully activated however at times the magnitude of the epb velocities and the plasma drifts are different from the neutral winds it is plausible that such a difference is due either to the effect of polarization electric fields developed inside the epb or due to the latitudinal gradient of the neutral winds and epb velocity measurements since the epb velocities are estimated at a higher latitude corresponding to an apex altitude of 400 km than the wind estimates which derive from an apex altitude of 250 km

incoherent scatter radar ionosonde and satellite measurements of equatorial f region vertical plasma drifts in the evening sector studies of equatorial f region evening vertical plasma drifts using different measurement techniques have produced conflicting results we examine the relationship of incoherent scatter radar and ionosonde drift observations over the peruvian equatorial region and ae e satellite drifts for different geophysical conditions our data show that there is large day to day variability on the ratios of radar and ionosonde drifts but on the average the measurements from these two techniques are in fair agreement during low and moderate solar flux conditions for high solar activity however the jicamarca evening drifts during equinox and december solstice are significantly larger than the ionosonde drifts these results can be explained by the different height ranges of the radar and ionosonde measurements and the increase of the upward drift velocity with height below the f region peak this altitudinal variation is related to the longitudinal gradient of the zonal plasma drifts as a result of the curl free electric field condition our results also indicate that during equinox the increase of the vertical prereversal velocity enhancement with solar activity is largely longitude independent

quiet time equatorial f region vertical plasma drift model derived from rocsat 1 observations 1 we have used five years of measurements on board the rocsat 1 satellite to develop a detailed quiet time global empirical model for equatorial f region vertical plasma drifts this model describes the local time seasonal and longitudinal dependence of the vertical drifts for an altitude of 600 km under moderate and high solar flux conditions the model results are in excellent agreement with measurements from the jicamarca radar and also from other ground based and in situ probes we show that the longitudinal dependence of the daytime and nighttime vertical drifts is much stronger than reported earlier especially during december and june solstice the late night downward drift velocities are larger in the eastern than in the western hemisphere at all seasons the morning and afternoon december solstice drifts have significantly different longitudinal dependence and the daytime upward drifts have strong wave number four signatures during equinox and june solstice the largest evening upward drifts occur during equinox and december solstice near the american sector the longitudinal variations of the evening prereversal velocity peaks during december and june solstice are anti correlated which further indicates the importance of conductivity effects on the electrodynamics of the equatorial ionosphere

simulation study of the longitudinal variation of evening vertical ionospheric drifts at the magnetic equator during equinox 1 quiet time low latitude ionospheric electric fields and vertical drifts in the evening sector at equinox are examined as a function of longitude and solar activity using simulations from the magnetosphere thermosphere ionosphere electrodynamics general circulation model mtiegcm the model inputs are held fixed with respect to universal time in order to evaluate the contributions to longitudinal variations of the equatorial electric fields and drifts associated with zonal variations in the geomagnetic field the simulated upward evening drift is somewhat larger than observations it increases with solar activity at a similar rate in all longitude sectors this rate about 0 32 0 37 m s per unit of 10 7 cm solar flux is quantitatively consistent with observations in the peruvian sector but is considerably greater than observations in the indian sector the simulations agree with observations in finding larger vertical drifts in the american atlantic sector than in the east asian pacific sector generally associated with longitudinal variations in the strength of the geomagnetic field relations among the longitude variations of the vertical drift the conductivity the eastward wind velocity the geomagnetic declination and gradients of the wind and declination are examined revealing few clear correlations however extrema of many of these quantities are noted in the american atlantic sector