error analysis for a long range lightning monitoring network of ground based receivers in europe 1 an experimental long range lightning detection system consisting of a network zeus of six ground based radio receivers has been deployed in europe and has been operated since june 2001 the receivers detect and measure the electromagnetic signal emitted by a lightning source in the very low frequency band between 5 and 15 khz sferics which propagates over thousands of kilometers in the earth ionosphere waveguide in this study lightning location retrievals from the zeus network are compared against more definitive sources in order to investigate issues on long range lightning retrieval accuracy and detection efficiency the validation study is carried out over three regions the u s east coast northwestern atlantic the african continent and within the network spain data originate from the u s national lightning detection network the lighting imaging sensor aboard the tropical rainfall measurement mission satellite and the spanish national lightning network we investigate the nature of the errors involved in the lightning location retrieval and propose a new approach for moderating some of these effects location errors are shown to vary between 40 and 400 km mode at 220 km for very long ranges 5000 km within the network the distance error does not exceed 40 km mode at 20 km random simulation results are shown to be in good agreement with validation data error reduction of 12 or 20 km at long range can be achieved by accommodating for the varying propagation velocities in the sferics wave the long range detection efficiency is shown to have a mode at approximately 20 and a relatively small spread with no obvious deviation from day to night

comparing e field changes aloft to lightning mapping data 1 a newly developed balloon borne instrument contains electric and magnetic sensors for determining how lightning alters electric field vectors relative to a coordinate system fixed with the earth by combining data from this instrument with results from the compact lightning mapping array lma at langmuir laboratory in central new mexico and the national lightning detection network nldn charge transported to ground by several strokes in a cloud to ground cg lightning flash can be quantified as the flash progresses the locations of the charge centers drained by successive strokes are seen to move further from the ground strike point using this new instrument and two different models to map lma source points onto charge centers the charge transported in an intracloud ic flash is also estimated details of the instrument design and data analysis are also presented

coordinated observations of sprites and in cloud lightning flash structure 1 the temporal and spatial development of sprite producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system mcs on 29 june 2011 near the oklahoma lightning mapping array lma sprites produced by a total of 26 lightning flashes were observed simultaneously on video from bennett colorado and hawley texas enabling a triangulation of sprites in comparison with temporal development of parent lightning in particular negatively charged stepped leaders in three dimensional space in general prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced typically 30 km however both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant lma sources with affinity to negative stepped leaders during the prior 100 ms interval multiple sprites appearing as dancing jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash by a single stroke through a series of current surges superposed on an intense continuing current or by both our observations imply that sprites elongated in one direction are sometimes linked to in cloud leader structure with the same elongation and sprites that were more symmetric were produced above the progression of multiple negative leaders this suggests that the large scale structure of sprites could be affected by the in cloud geometry of positive charge removal based on an expanded dataset of 39 sprite parent flashes by including more sprites recorded by one single camera over the same mcs the altitude above mean sea level msl of positively charged cloud region tapped by sprite producing strokes declined gradually from 10 km msl 35 c to around 6 km msl 10 c as the mcs evolved through the mature stage on average the positive charge removal by causative strokes of sprites observed on 29 june is centered at 3 6 km above the freezing level or at 7 9 km above ground level

very low frequency sferic bursts sprites and their association with lightning activity 1 recent observations have revealed the occurrence of burst like vlf activity lasting from tens of milliseconds up to a few seconds associated with the onset of many sprites these sferic bursts are thought to be due to the horizontal in cloud component of lightning activity since they have been observed to propagate only short distances a few hundred kilometers in the earth ionosphere waveguide and are generally not reported by lightning detection networks the possible involvement of in cloud lightning in sprite production has been previously suggested on the basis of the observed long delays and spatial displacement between causative cloud to ground cg discharges and sprite events in this work we investigate the association between sprites and sferic bursts using vlf data and a large set of sprite observations between 1995 and 2000 we compare the occurrence of sferic bursts in association with sprites for thousands of observations through many different dates and thunderstorms results indicate that sprite causative cgs are more commonly found in association with bursts of sferic activity than those cg discharges without sprites and that furthermore the distribution of sferic burst vlf energy is significantly higher for sprite associated events we further investigate the source of these bursts by comparing vlf data to lightning mapping array lma data of vhf pulses due to lightning such comparisons show that most sferic burst events can be explained as radiation from the horizonal in cloud components of cg lightning as detected by the lma

mesospheric sprite current triangulation a network of three time synchronized high precision induction coil magnetometers is installed in north america to measure sprite associated lightning flash waveforms in the frequency range 0 1 1000 hz during the energetics of upper atmosphere excitation by lightning 1998 sprite campaign in july 1998 simultaneous intensified video observations on board an aircraft are used to investigate 16 sprites with long time delays 33 33 ms relative to the parent lightning discharge reported by the national lightning detection network three different long delayed sprite associated waveforms can be distinguished 38 do not exhibit any significant magnetic intensity variation 25 exhibit slow variations 100 ms and 25 exhibit short pulses 4 ms the source locations of the sprite associated short pulses are triangulated by use of arrival time difference analysis one source location exhibits a substantial spatial displacement 60 km relative to the parent lightning discharge in agreement with the azimuths of sprite luminosity edges determined from the corresponding background star field of the video observations on board the aircraft it is concluded from the temporal and spatial coincidence of the secondary short pulse and the sprite luminosity that this particular sprite is associated with current in the mesosphere

new high resolution ground based studies of sprites new observations of sprites cloud ionosphere luminous discharges above thunderstorms were made from the yucca ridge field station 20 km northeast of fort collins colorado on the night of july 11 12 1994 as part of a summer 1994 observing campaign the sprites appeared above a moderate mesoscale convective complex mostly over kansas at a range of about 270 km the sprites were observed with both wide field and telescopic image intensified ccd tv cameras a telescopic photometer system and a 1 to 50 khz band vlf sferics receiver this paper is based on five 1 s data intervals containing bright sprites smaller sprites and cloud and sky flashes telescopic tv images of bright sprites had a fan shaped upper plume with very fine features not well resolved by the tv but dendritic upward forked and vertically striated forms adjacent to these plumes and bright points of luminosity around the plume shaped regions many sprites consisted entirely of groups of vertically aligned striations which sometimes appeared to diverge from a common point of origin at cloud tops all sprites in the present data sample were preceded by a cloud to ground cg stroke with a coincident sferic and sky flash all cg strokes associated with sprites were positive and most were 100 ka or more inferred peak current from the photometer the duration of the cg induced sky flashes was about 3 ms and the additional sprite total light curve was also about 3 ms the puzzling feature that the total duration of tv images of sprites was often longer than the photometric values is discussed and an explanation given the sprites were attributed to strong negative charging following the positive cg stroke of a localized cloud top region which produced an intense electric field and a luminous discharge in the cloud ionosphere region the concept of break even electric fields suggested by mccarthy and parks may explain discharge initiation with moderate field strengths

nitrogen and trace elements in tektites and impact glasses abstract nitrogen and several trace elements have been studied in samples of one muong nong tektite irghizites tektite like glass zhamanshinites impactites and several obsidian glasses a detailed investigation of inter and intra layer samples from the muong nong tektite shows a chemical heterogeneity both within and between the layers in general the elemental variations seem to be due to a varying feo content irghizites both sio2 rich and sio2 poor are compositionally more homogeneous than the zhamanshinites the heterogeneous distribution of nitrogen observed in the muong nong tektite and the zhamanshinites is unlike that in any other tektite studied so far this shows clearly that zhamanshinites have suffered lower peak temperatures than irghizites and muong nong tektites lower ones than normal splash form tektites available chemical and petrological data on muong nong tektites suggest that they were formed by in situ melting of soil

huge variations in the isotopic ratio 196hg 202hg in some acid insoluble residues of sikhote alin and other iron meteorites the insoluble materials obtained on dissolution of iron meteorites in 2 m h2so4 have been analysed by radiochemical neutron activation to measure the isotopic ratio 196hg 202hg of hg released at different temperatures in many cases this ratio is found to be anomalous its extreme values relative to the reagent hg being 0 003 2 limit and 1 26 0 05 often in the same residue both positive and negative deviations are found at different temperatures the anomalous normal and isotopically diluted hg distillates have been re irradiated to eliminate the influence of neutron self shielding and interfering reactions from matrix elements the isotopic anomaly persists in the distillates proving that any artifacts during irradiation are essentially absent the presence of isotopically anomalous hg in iron meteorites puts some severe constraints on the formation history of these objects either iron meteorites have been formed in a non magmatic process entrapping presolar grains or some foreign matter has been injected into their solidified parent bodies by collisions with objects of different isotopic composition

preliminary results from the sprites94 aircraft campaign 1 red sprites the dual jet aircraft sprites94 campaign yielded the first color imagery and unambiguously triangulated physical dimensions and heights of upper atmospheric optical emissions associated with thunderstorm systems low light level television images in both color and in black and white b w obtained during the campaign show that there are at least two distinctively different types of optical emissions spanning part or all of the distance between the anvil tops and the ionosphere the first of these emissions dubbed sprites after their elusive nature are luminous structures of brief 16 ms duration with a red main body that typically spans the altitude range 50 90 km and possessing lateral dimensions of 5 30 km faint bluish tendrils often extend downward from the main body of sprites occasionally appearing to reach cloud tops near 20 km in this paper the principal characteristics of red sprites as observed during the sprites94 campaign are described the second distinctive type of emissions blue jets are described in a companion paper wescott et al this issue

non cosmogenic lithium 6 in iron meteorites a neutron activation method is used to measure6li via the reaction6li n 3h in iron meteorites it is found that most6li occurs in non metallic inclusions which can be separated by dissolution of the metal in 4 m h2so4 the non magnetic portion of such a residue has as high as 0 9 ppm6li while in the bulk sample6li ranges from 0 02 to 10 ppb average6li contents ppb for various classes are ia 1 8 iiab 1 6 and iiia 0 4 cosmic ray produced6li is generally much smaller than the native6li

performance evaluation of the u s national lightning detection network in eastern new york 2 location accuracy we have evaluated the location accuracy of the u s national lightning detection network nldn via comparison of individual nldn stroke locations with their corresponding stroke terminations as determined from multiple site video recordings of local cloud to ground lightning flashes the video records used in this analysis were acquired in the vicinity of albany new york during the summers of 1994 and 1995 seasons corresponding to the initial and final phases of the upgrade of the nldn to the improved accuracy from combined technology impact configuration for 1994 a total of 751 strokes were located in common between the video and nldn data sets yielding median and mean values of the nldn video location separation of 2 21 km and 3 74 km respectively constraint of the 1994 data to the best video locations those with a semimajor axis value of the 50 error ellipse less than 500 m yielded a subset of 53 strokes with median and mean values of the nldn video location separation of 2 61 km and 4 74 km respectively for 1995 a total of 219 strokes were located in common yielding median and mean values of the nldn video location separation of 442 m and 865 m respectively constraint of the 1995 data to that year s best video locations those with a semimajor axis value of the 50 error ellipse less than 200 m yielded a subset of 79 common strokes with median and mean values of the nldn video location separation of 435 m and 625 m respectively the impact upgrade of the nldn apparently has resulted in about a fivefold increase in location accuracy a special subset of 11 strokes occurred in 1995 these were located by the nldn and observed to terminate on local structures of accurately known location for these 11 strokes the median and mean values of the nldn location error are 518 m and 484 m respectively a result quite consistent with the overall nldn video location comparison and the claimed 500 m median location accuracy for the upgraded network indeed we argue that removal of an apparent residual bias in the nldn locations ultimately could yield a median location accuracy in this region approaching 250 m finally we find that the nldn location error is a function of the estimated stroke peak current with the weakest peak currents having the poorest locations for both years for the 1995 data strokes with peak currents of intermediate magnitude 20 30 ka were the most accurately located

systematic deviations in source direction estimates of q bursts recorded at nagycenk hungary q bursts are globally detectable extremely low frequency elf 3 3000hz band wave packets produced by intense lightning discharges q bursts recorded in the szechenyi istvan geophysical observatory nck 16 7 e 47 6 n hungary on 1 and 2 august 2012 have been analyzed to find azimuths of their sources the location of parent lightning strokes of 320 and 205 q bursts on the 2days respectively have been identified in the records of the world wide lightning location network wwlln using the detection times at nck elf data based source azimuths were found to differ systematically from source azimuths obtained from wwlln lightning locations the difference between the corresponding azimuth values depends on the azimuth of the source this variation of the source azimuth error mirrors the symmetry of the conductance of the earth s crust inferred from magnetotelluric measurements around nck after correction for the azimuthal dependence the variation of the residual error shows a diurnal pattern with positive azimuth deviations occurring near midnight local time fullekrug and sukhorukov 1999 suggested that the anisotropic conductivity in the earth s crust below the observatory and the different daytime and nighttime conductivities in the lower ionosphere respectively may cause the identified error terms our results emphasize the substantial effect of anisotropic conductivity in the earth s crust around the recording station on the accuracy of elf direction finding the need for theoretical approach and more measurements is pointed in understanding the underlying mechanisms quantitatively and in investigating whether elf observations can be used in geophysical prospecting 2016 american geophysical union all rights reserved

on remote sensing of transient luminous events parent lightning discharges by elf vlf wave measurements on board a satellite first recordings of satellite elf vlf waveform data associated with transient luminous event tle observations are reported from the summer 2005 campaign coordinated by stanford university and laboratoire de physique et chimie de l environnement et de l espace lpce tles are optically observed from the u s langmuir laboratory while elf vlf waveform data are simultaneously recorded on board the centre national d etudes spatiales microsatellite demeter and on the ground at langmuir analyses of elf vlf measurements associated with sprite events observed on 28 july 2005 and 3 august 2005 are presented

lithostratigraphy and geochemistry of the cottrells cove group buchans roberts arm volcanic belt new constraints for the paleotectonic setting of the notre dame subzone newfoundland appalachians new sedimentological geochemical and geochronological data from the cottrells cove group in central newfoundland provide important constraints on the nature of the notre dame subzone its tectonic setting and the history of the laurentian margin during the early ordovician the cottrells cove group forms the eastern extension of the roberts arm group and correlates with the chanceport group on new world island it is represented by two volcano sedimentary formations that occur in a complex thrust stack the fortune harbour formation consists of calc alkalic island arc lavas followed by a 1250 m thick succession of volcaniclastic deposits radiolarian cherts and calc alkalic mafic flows which were deposited in a back arc basin plain setting the volcaniclastic deposits include felsic tuff which has a u pb zircon age of 484 f 2 ma and an inheritance component of 2517 f 26 ma these new u pb and nd isotope data suggest that the island arc back arc volcanism and sedimentation in the notre dame subzone developed in the vicinity of continental margin and approximately 10 ma earlier than has previously been established the moores cove formation is undated but contains boulders of calc alkalic basalt and is presumed to be at least in part younger than the fortune harbour formation tholeiitic lavas together with associated radiolarian cherts and volcaniclastic deposits constitute the basal part of the moores cove formation and may have been deposited in a back arc environment synchronously with some parts of the fortune harbour formation they are conformably followed by an over 1200 m thick coarsening upward succession of lower slope and submarine fan deposits the polymictic flysch containing clasts of island arc basalt accompanied by other volcanic plutonic ultramafic and sedimentary detritus may record middle or upper ordovician uplift and erosion of obducted arc back arc volcano sedimentary sequences and their ophiolitic substrate

evidence for continuing current in sprite producing cloud to ground lightning radio atmospherics launched by sprite producing positive cloud to ground lightning flashes and observed at palmer station antarctica exhibit large elf slow tails following the initial vlf portion indicating the presence of continuing currents in the source lightning flashes one to one correlation of sferics with nldn lightning data in both time and arrival azimuth measured with an accuracy of 1 at 12 000 km range allows unambiguous identification of lightning flashes originating in the storm of interest slow tail measurements at palmer can potentially be used to measure continuing currents in lightning flashes over nearly half of the earth s surface

forte radio frequency observations of lightning strokes detected by the national lightning detection network this work compares simultaneous observations of lightning from two complementary systems forte is a low earth orbit satellite carrying radiowave and optical instruments for the study of lightning the radio receivers aboard forte observe very high frequency vhf emissions from the air breakdown process preceding and sometimes accompanying a lightning current the national lightning detection network nldn is a ground based array of sensors in the contiguous united states observing the low frequency lf and very low frequency vlf radiation from vertical currents prior to the launch of forte in 1997 essentially no work had been done on the statistical correlations between 1 ground based lf vlf and 2 spaced based vhf remote sensing of lightning during a 6 month campaign in april september 1998 forte took most of its triggered vhf data over and near the contiguous united states and nldn data were specially postprocessed in a loosened criterion mode providing enhanced detection range beyond the coastline and borders of the array itself the time history of reported events from the two systems was compared and event pairs each pair containing one event from forte the other from nldn which were candidate correlations closer than 200 ms from each other were scrutinized to determine whether the members of a pair actually came from the same discharge process we have found that there is a statistically significant correlation for a subset of forte events this correlation is most likely to occur for intracloud and less likely to occur for cloud to ground discharges the correlated vhf and nldn events tend to occur within 30 s of each other after correction for the propagation of the vhf signal to forte from the nldn geolocated stroke location most correlations outside of 30 s turn out to be merely a statistical accident the nldn furnished geolocation allows the correlated forte detected vhf pulses to be better interpreted in particular we can deduce from the lag of the vhf ground reflection echo the height of the vhf emission region in the storm

vlf signatures of ionospheric perturbations caused by lightning discharges in an underlying and moving thunderstorm a sequence of vlf events first of early fast type then of lep type observed at poitiers on the amplitude of the signal from the gqd 19 02 khz transmitter in england is analysed vlf data sampled at 100 ms intervals are combined with sferics and meteorage data on lightning ground strikes detected within a 50 km belt centered on the vlf path both the slowly and rapidly recovering early fast events are observed in association with intense positive cg flashes located in the baie de seine l 2 25 at a distance less than 35 km from the vlf path the lep events are observed when the storm initially overlapping the path moves southeastwards some early fast events are also observed on the very short path hwu 18 3 khz poitiers

localization of individual lightning discharges via directional and temporal triangulation of sferic measurements at two distant sites 1 lightning discharges generate electromagnetic pulses known as sferics that propagate through the waveguide formed by the earth and the ionosphere the energy in the vlf band can propagate over great distances 10 000 km with low loss 3 db mm and can therefore be detected far from the source lightning location using sferic measurements from vlf receivers at palmer station antarctica and vieques island puerto rico the locations of lightning discharges from regions such as south america north america and africa are triangulated both sferic arrival azimuth at the two receivers and the time of arrival difference between the receivers are used to find the best estimate of the lightning discharge location owing to the extremely wide separation of the two receivers ambiguities sometimes result in pairing sferics detected at one site to their matching sferics detected at the other site in these cases a best best estimate scheme is used simulation results indicate that for the two receivers considered here the most accurate location performance is in south america with an expected median location error of 75 km the system has the worst performance due north of the vieques island site with an expected median location error of 2000 km triangulation results for south america are shown for the period 7 10 september 2001 results for 8 september 2001 are compared to cloud to ground lightning flashes detected by the national lightning detection network for this day 49 of flashes were detected with a median error of about 200 km results are also compared to lightning discharges detected by the lightning imaging sensor lis aboard the tropical rainfall measuring mission trmm satellite for a particular trmm pass over south america 20 of flashes detected by lis were correctly located using the described technique with a median error of 187 km the event rate for a localized south american storm is also monitored and documented for the same 4 day period

implications of lightning charge moment changes for sprite initiation 1 we report impulse lightning charge moment changes defined as occurring in the first 2 ms after return stroke onset in all cloud to ground lightning strokes detected by the national lightning detection network in three storms during which above thunderstorm sprite video was recorded after analyzing strokes that both did and did not produce sprites and carefully accounting for lightning sprite delay times we found that sprite initiation on all three nights is consistent with a sharp charge moment threshold essentially all charge moment changes above and none below this threshold produced sprites with short delays 5 ms from the source lightning on two nights this threshold was approximately 600 c km and on the other it was approximately 350 c km this internight variability is probably due to expected variability in the nighttime mesospheric conductivity and the thresholds themselves are consistent with predictions of conventional breakdown theory additionally we found only one negative polarity lightning stroke from all three storms that exceeded this threshold indicating that the rarity of documented sprites produced by negative strokes may be largely explained by the lack of sufficiently big negative strokes in the u s high plains

sprites triggered by negative lightning discharges high altitude air breakdown manifested as red sprites is reported in close association with negative cloud to ground lightning cg on at least two occasions above an unusual storm on august 29 1998 data from high speed photometry low light level video and receivers of lightning electromagnetic signatures in the frequency range 10 hz to 20 khz are used to establish the association and indicate that the causative cg discharges effected unusually large vertical charge moment changes mqv of up to 1550 c km in 5 ms the existence of sprites caused by cg s rather than the regularly associated cg s has immediate implications for sprite models and observations

on the association of terrestrial gamma ray bursts with lightning and implications for sprites measurements of elf vlf radio atmospherics sferics at palmer station antarctica provide evidence of active thunderstorms near the inferred source regions of two different gamma ray bursts of terrestrial origin fishman et al 1994 in one case a relatively intense sferic occurring within 1 5 ms of the time of the gamma ray burst provides the first indication of a direct association of this burst with a lightning discharge this sferic and many others launched by positive cloud to ground cg discharges and observed at palmer during the periods studied exhibit slow tail waveforms indicative of continuing currents in the causative lightning discharges the slow tails of these sferics are similar to those of sferics originating in positive cg discharges that are associated with sprites

sprite observations above the u s high plains in relation to their parent thunderstorm systems transient luminous events sprites blue jets elves above large mesoscale convective systems mcss over the u s high plains have been routinely monitored from the yucca ridge field station near fort collins colorado using ground based low light video systems we analyzed 36 sprites above the nebraska mcs of august 6 1994 the results lend further support to the hypothesis that sprites are almost uniquely associated with positive cloud to ground cg lightning flashes sprite associated cgs also averaged substantially larger peak currents than the remaining cg population 81 ka versus 30 ka in this storm system there is some evidence that sprite associated cgs also have higher stroke multiplicity this study yields no evidence of sprites associated with negative cg events in the central united states an additional requirement appears to be that the parent mcs has a contiguous radar reflectivity area exceeding 20 25 000 km 2 the majority of the sprites occur above the large stratiform precipitation region and not the high reflectivity convective core of the mcs triangulation of a limited number of paired images from september 7 1994 suggests that the sprite is generally centered within 50 km of the parent cg assuming the cg provides the range single image photogrammetric analyses provide estimates of the maximum vertical extent of the sprites for this storm the sprite tops averaged 77 km with a maximum of 88 km the bases averaged 50 km but with a few sprite tendrils extending as low as 31 km

global triangulation of intense lightning discharges a global network of three electromagnetic measurement instruments is used to simultaneously record time series of globally observable extremely low frequency elf magnetic field disturbances which propagate with little attenuation around the globe within the earth ionosphere cavity the triangulation of individual lightning flashes results in a picture of the temporal evolution of intense lightning discharge occurrences on the planetary scale during april 1998 the lightning flash charge moments are calculated with the short pulse approximation of the normal mode expansion the majority of the triangulated lightning discharges exhibit charge moments with a potential to excite mesospheric sprites and 5 20 may account for air breakdown at sprite altitudes in 50 70 km height

the effects of vertical wind shear on the distribution of convection in tropical cyclones abstract the influence of vertical wind shear on the azimuthal distribution of cloud to ground lightning in tropical cyclones was examined using flash locations from the national lightning detection network the study covers 35 atlantic basin tropical cyclones from 1985 99 while they were over land and within 400 km of the coast over water a strong correlation was found between the azimuthal distribution of flashes and the direction of the vertical wind shear in the environment when the magnitude of the vertical shear exceeded 5 m s 1 more than 90 of flashes occurred downshear in both the storm core defined as the inner 100 km and the outer band region r 100 300 km a slight preference for downshear left occurred in the storm core and a strong preference for downshear right in the outer rainbands the results were valid both over land and water and for depression storm and hurricane stages it is argued that in convectively active tropical cyclones deep divergent circulations oppose the ver

compaction of wyodak coal powder river basin wyoming u s a abstract precise measurements of 54 deformed tree trunks within the subbituminous wyodak coal seem in northeastern wyoming were made at eight locations in surface mines along the outcrop north and south of gillette theory of elasticity applied to the individual measurements gives ratios of peat thickness to coal thickness which range from 1 7 1 to 31 1 and average 7 1 1 this result is similar to those previously determined by other methods in other locations statistical analysis establishes to a high degree of confidence however that the ratios for each mine site vary widely and cannot be considered to be constant or to vary uniformly within the study area

depositional models for two tertiary coal bearing sequences in the powder river basin wyoming usa depositional controls on peat forming environments which produce thick 10m coal beds can be inferred from relationships between coal bed geometry maceral composition and associated lithologies study of these relationships within sedimentary sequences associated with the wyodak anderson palaeocene and the felix eocene sub bituminous coal beds in the powder river basin wyoming usa suggests two modes of fluvially controlled peat accumulation the wyodak anderson peat is interpreted to have formed in restricted parts of the floodplain that were separated by deposits of contemporaneous anastomosed channels the channels and associated sediments maintained their position through time because they were confined by thick deposits of raised wyodak anderson peat in contrast the felix coal bed is interpreted to have formed as a raised but widespread peat on an abandoned platform of meander belt sands the purpose of this paper is to compare and contrast two different fluvial depositional settings that produced anomalously thick 10m coal deposits in the intermontane powder river basin of wyoming usa these models may be useful as predictive tools for coal exploration and production

comparison of photometric measurements and charge moment estimations in two sprite producing storms 1 in one relatively small storm on july 2 2000 276 sprites were observed between 04 00 07 00 ut these sprites were largely confined to 70 85 km altitude were relatively faint and diffuse and were typically associated with very high peak currents and short time duration a second storm on july 4 2000 had a much larger spatial extent and 27 sprites were observed between 04 00 07 00 ut in a wide range of shapes and time scales spanning 40 90 km altitude these sprites were produced by 20 120 ka cg s had complex optical signatures and were frequently associated with observed elf radiation we hypothesize that relatively small storms mainly produce sprites in the form of diffuse glow whereas larger storms with higher cloud tops can initiate streamer discharges leading to more spectacular sprites

elf sferic energy as a proxy indicator for sprite occurrence broadband elf vlf measurements of sferics near ft collins colorado demonstrate that elf sferic en ergy is a proxy for sprite occurrence which can be used to estimate the number of sprites produced by a thunderstorm ultra long range 12 000 km measurements at palmer station antarctica conrm the application of this proxy to storms where no video observations of sprites are avail able comparison with high resolution photometer measure ments demonstrate the simultaneity of sprite luminosity and an elf second pulse believed to be radiated by electri cal currents within the sprite body cummer et al 1998 measurements of the second elf pulse are used to identify a quantitative relationship between the current in sprites and total sprite luminosity

the contribution of anisotropic conductivity in the ionosphere to lightning flash bearing deviations in the elf ulf range lightning flash bearing deviations in the elf ulf range are monitored at two independently operating measurement instruments in hollister california and silberborn germany the lightning flash bearing deviation at hollister exhibits a rotational dependence 12 associated with the conductivity contrast between the earth s crust and the nearby pacific ocean the bearing deviations at both stations exhibit a pronounced diurnal local time variation 11 this diurnal variation is attributed to the anisotropic conductivity in the ionosphere during day and nighttime conditions no bearing deviation dependency from the source receiver distance can be distinguished correction for the mean rotational dependence at hollister and the mean diurnal variation at both locations results in residual bearing deviations 10 which are related to the variability of anisotropic conductivity in the ionosphere on a subdiurnal time scale

tropical cyclone formation in a sheared environment a case study abstract the development of hurricane danny 1997 from depression to hurricane was examined using cloud to ground lightning data reconnaissance aircraft data and satellite imagery vertical wind shear between 850 and 200 hpa of 5 11 m s 1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development early in the period the storm intensified steadily in the presence of this downshear convection during the last and most intense outbreak a second vortex appeared to develop within the convection evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original based on these events it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process equivalent potential temperature fields within 500 m of the surface were examined only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of eq

mesoscale aspects of the downshear reformation of a tropical cyclone the downshear reformation of tropical storm gabrielle 2001 was investigated using radar reflectivity and lightning data that were nearly continuous in time as well as frequent aircraft reconnaissance flights initially the storm was a marginal tropical storm in an environment with strong 850 200 hpa vertical wind shear of 12 13 m s 1 and an approaching upper tropospheric trough both the observed outflow and an adiabatic balance model calculation showed that the radial vertical circulation increased with time as the trough approached convection was highly asymmetric with almost all radar return located in one quadrant left of downshear in the storm reconnaissance data show that an intense mesovortex formed downshear of the original center this vortex was located just south of rather than within a strong downshear left lightning outbreak consistent with tilting of the horizontal vorticity associated with the vertical wind shear the downshear mesovortex contained a 972 hpa minimum central pressure 20 hpa lower than minimum pressure in the original vortex just 3 h earlier the mesovortex became the new center of the storm but weakened somewhat prior to landfall it is argued that dry air carried around the storm from the region of upshear subsidence as well as the direct effects of the shear prevented the reformed vortex from continuing to intensify despite the subsequent weakening of the reformed center it reached land with greater intensity than the original center it is argued that this intensification process was set into motion by the vertical wind shear in the presence of an environment with upward motion forced by the upper tropospheric trough in addition the new center formed much closer to the coast and made landfall much earlier than predicted such vertical shear induced intensity and track fluctuations are important to understand especially in storms approaching the coast

telescopic imaging of sprites telescopic images of sprites show a wide variety of generally vertical but also slanted fine structure including branching tree like shapes and well defined but isolated columns with transverse spatial scales ranging from tens of meters to a few hundred meters at 60 85 km altitude simultaneous analysis of radio atmospheric and lightning data indicates that specific columnar regions are selectively excited by successive discharges