charge transfer and in cloud structure of large charge moment positive lightning strokes in a mesoscale convective system 1 lightning observations in the very high frequency band and measurements of ultra low frequency magnetic fields are analyzed to investigate the charge transfer and in cloud structure of eight positive cloud to ground cg strokes in a mesoscale convective system although no high altitude images were recorded these strokes contained large charge moment changes 1500 3200 c km capable of producing nighttime sprites even though the convective region of the storm was where the flashes originated and where the cg strokes could occur the charge transferred to ground was mainly from the stratiform region the post stroke long continuing currents were connected to highly branched negative leader extension into the stratiform region while the storm dissipated the altitude of negative leader propagation in the stratiform area dropped gradually from 8 to 5 km indicating that in some and perhaps all of these strokes it was the upper positive charge in the stratiform region that was transferred

preliminary results from the sprites94 aircraft campaign 2 blue jets initial observations of a newly documented type of optical emission above thunderstorms are reported blue jets or narrowly collimated beams of blue light that appear to propagate upwards from the tops of thunderstorms were recorded on b w and color video cameras for the first time during the sprites94 aircraft campaign june july 1994 the jets appear to propagate upward at speeds of about 100 km s and reach terminal altitudes of 40 50 km fifty six examples were recorded during a 22 minute interval during a storm over arkansas we examine some possible mechanisms but have no satisfactory theory of this phenomenon

transient luminous events above two mesoscale convective systems storm structure and evolution 1 two warm season mesoscale convective systems mcss were analyzed with respect to their production of transient luminous events tles mainly sprites the 20 june 2007 symmetric mcs produced 282 observed tles over a 4 h period during which the storm s intense convection weakened and its stratiform region strengthened tle production corresponded well to convective intensity the convective elements of the mcs contained normal polarity tripole charge structures with upper level positive charge 40 c midlevel negative charge 20 c and low level positive charge near the melting level in contrast to previous sprite studies the stratiform charge layer involved in tle production by parent positive cloud to ground cg lightning resided at upper levels this layer was physically connected to upper level convective positive charge via a downward sloping pathway the average altitude discharged by tle parent flashes during tle activity was 8 2 km above mean sea level msl 25 c the 9 may 2007 asymmetric mcs produced 25 observed tles over a 2 h period during which the storm s convection rapidly weakened before recovering later unlike 20 june tle production was approximately anticorrelated with convective intensity the 9 may storm which also had a normal tripole in its convection best fit the conventional model of low altitude positive charge playing the dominant role in sprite production however the average altitude discharged during the tle phase of flashes still was higher than the melting level 6 1 km msl 15 c based on these results it is inferred that sprite production and sprite parent positive charge altitude depend on mcs morphology

lithology and biostratigraphy of franciscan like chert and associated rocks in west central baja california mexico we present the result of biostratigraphic and lithologic studies of ribbon chert and associated rocks in a mesozoic subduction complex in west central baja california mexico the subduction complex terrane is divided into three subterranes each of which consists of an originally coherent sequence of interbedded oceanic rocks including ocean floor basalt terrigenous siliciclastic turbidites radiolarian ribbon chert and limestone parts of the original stratigraphy are preserved in the least deformed least metamorphosed subterrane ocean floor pillow basalt on cedros island is overlain by about 40 m of radiolarian ribbon chert ranging in age from early jurassic or older to early cretaceous the chert is overlain by thin bedded turbidites on san benito west island radiolarian ribbon chert is interbedded with volcanogenic rocks including a megabreccia that contains blocks of metabasites folded late jurassic early cretaceous chert and marble in a mid cretaceous radiolarite matrix chert samples from tectonically thinned sequences elsewhere on cedros and san benito islands contain late triassic to early cretaceous radiolarian assemblages the 40 m thick chert section on cedros island probably accumulated atop oceanic crust in a large ocean basin for at least 65 m y and was later capped by terrigenous turbidites as it approached the subduction zone along the western margin of north america faulted chert sections on cedros and san benito central and west islands are subsets of the main section on cedros island the chert megabreccia section on san benito west island is interpreted to have accumulated at the foot of a volcanic edifice on the ocean floor for example seamount fracture zone or during extension and normal faulting of the downgoing oceanic plate in a subduction zone sedimentary structures and stratigraphic relations indicate that all ribbon chert in this subduction complex was deposited by sediment gravity flows that is they are turbidites

electrical structure in thunderstorm convective regions 1 mesoscale convective systems electric field e soundings through convective regions of mesoscale convective systems mcss are examined in this paper ten e soundings through updrafts in mcs convective regions and five soundings in mcs convective regions outside updrafts are used to show that a typical electrical structure exists in this region these 15 e soundings plus one other previously published sounding which is included in this analysis comprise all known soundings in the convective region of mcss the basic charge structure identified in mcs updrafts consists of four charge regions alternating in polarity with the lowest region positive and the highest region negative the basic charge structure outside updrafts in mcs convective regions has six charge regions alternating in polarity with a positive charge region lowest maximum e magnitudes of both polarities are larger and are located at lower heights in soundings outside updrafts compared to those within updrafts excepting the upper positive charge inferred charge regions are shallower and have larger charge densities outside updrafts the center of the main negative charge is lower and warmer outside updrafts 5 5 km 6 2 c than within updrafts 6 9 km 15 7 c these features inside and outside updrafts are incorporated in a new conceptual model of mcs convective region charge structure also an expanded conceptual model is developed using previously published data from other parts of mcss this more complete conceptual model shows the typical electrical charge airflow and reflectivity features in the stratiform region the transition zone and the convective region of midlatitude mesoscale convective systems

effects of charge and electrostatic potential on lightning propagation 1 three dimensional lightning mapping observations are compared to cloud charge structures and electric potential profiles inferred from balloon soundings of electric field in new mexico mountain thunderstorms for six individual intracloud and cloud to ground flashes and for a sequence of 36 flashes in one storm the comparisons consistently show good agreement between the altitudes of horizontal lightning channels and the altitudes of electric potential extrema or wells lightning flashes appear to deposit charge of opposite polarity in relatively localized volumes within the preexisting lower positive midlevel negative and upper positive charge regions associated with the potential wells the net effect of recurring lightning charge deposition at the approximate levels of potential extrema is to increase the complexity in the observed storm charge structure the midlevel breakdown of both normal intracloud flashes and negative cloud to ground flashes is observed to be segregated by flash type into the upper and lower parts of the deep potential well associated with the midlevel negative charge the segregation is consistent with perturbations observed in the bottom of the negative potential well due to embedded positive charge that was probably deposited by earlier flashes it is also consistent with an expected tendency for vertical breakdown to begin branching horizontally before reaching the local potential minimum the joint observations reconcile the apparent dichotomy between the complex charge structures often inferred from balloon soundings through storms and the simpler structures often inferred from lightning measurements

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

a gps based three dimensional lightning mapping system initial observations in central new mexico a gps based system has been developed that accurately locates the sources of vhf radiation from lightning discharges in three spatial dimensions and time the observations are found to reflect the basic charge structure of electrified storms observations have also been obtained of a distinct type of energetic discharge referred to as positive bipolar breakdown recently identified as the source of trans ionospheric pulse pairs tipps observed by satellites from space the bipolar breakdown has been confirmed to occur between the main negative and upper positive charge regions of a storm and found to be the initial event of otherwise normal intracloud discharges the latter is contrary to previous findings that the breakdown appeared to be temporally isolated from other lightning in a storm peak vhf radiation from the energetic discharges is observed to be typically 30 db stronger than that from other lightning processes and to correspond to source power in excess of 100 kw over a 6 mhz bandwidth centered at 63 mhz

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

on the series of cg lightning strokes in dancing sprite events in dancing sprite events sprite entities and groups appear in rapid succession together with a corresponding series of parent lightning strokes dancing sprite events including a case with possible sprite rebrightening were recorded on video simultaneously from two observation sites above a mesoscale convective system in central europe on the night of 6 august 2013 joint analysis of triangulated locations of sprite elements position type and peak current of lightning strokes from the linet lightning detection network database and current moment waveforms deduced at the hylaty station poland showed that subsequent sprite parent lightning strokes occurred no further than 21 km from the closest preceding sprite entity in the cases analyzed in this study additionally it was found that longer sprite delay times tend to correspond to larger sprite location offsets from the parent cg stroke these observations the occurrence of cg lightning stroke and sprite sequences as well as sprite sprite delay times and displacements can be explained if cg strokes are part of one extended lightning flash a corresponding production mechanism based on previous findings on the formation of sprite producing and general cg lightning discharges is suggested plain language summary in dancing sprite events sprites appear in rapid succession together with a corresponding series of parent lightning strokes dancing sprite events were recorded on video simultaneously from two observation sites above an extended thunderstorm system in central europe on the night of 6 august 2013 comparison of triangulated sprite locations and the locations of corresponding lightning activity revealed that subsequent sprite parent lightning strokes occurred below or relatively near the location of the closest preceding sprite entity in the examined cases in this paper a mechanism is suggested for the development of lightning flashes that produce dancing sprites the proposed mechanism accounts for prompt and delayed sprites relative to their parent lightning stroke highlights the role of the variation of lightning current in sprite production and can explain the observed closeness of the next cg lightning stroke to the area of previous sprites

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

television image of a large upward electrical discharge above a thunderstorm system an image of an unusual luminous electrical discharge over a thunderstorm 250 kilometers from the observing site has been obtained with a low light level television camera the discharge began at the cloud tops at 14 kilometers and extended into the clear air 20 kilometers higher the image which had a duration of less than 30 milliseconds resembled two jets or fountains and was probably caused by two localizd electric charge concentrations at the cloud tops large upward discharges may create a hazard for aircraft and rocket launches and by penetrating into the ionosphere may initiate whistler waves and other effects on a magnetospheric scale such upward electrical discharges may account for unexplained photometric observations of distant lightning events that showed a low rise rate of the luminous pulse and no electromagnetic sferic pulse of the type that accompanies cloud to earth lightning strokes an unusually high rate of such photometric events was recorded during the night of 22 to 23 september 1989 during a storm associated with hurricane hugo

climatic and volcanic forcing of tropical belt northern boundary over the past 800 years the position of the northern boundary of the tropical belt affects the hydroclimate of many arid and semi arid regions in the northern hemisphere widening of the tropical belt since the 1970s has largely been attributed to anthropogenic forcing however the relative influence of natural drivers of tropical belt expansion and contraction before this time is poorly understood here we use data on tree ring widths from five mid latitude regions in the northern hemisphere to reconstruct the movement of the northern boundary of the early spring tropical belt over the past 800 years ad 1203 2003 our reconstruction explains 45 of the interannual variance in the latitudinal extent of the hadley circulation a metric of the position of the tropical belt boundary we find that the tropical belt contracted expanded during positive negative phases of the el nino southern oscillation and pacific north american teleconnection patterns the tropical belt also contracted significantly following major volcanic events that injected sulfur into the stratosphere the longest period of persistent tropical belt expansion occurred in the late sixteenth century during one of the coldest periods of the little ice age our results warn of potential socio economic consequences of future variations in tropical belt width driven by natural climate variability or stratospheric aerosol injections whether volcanic or artificial climate variability and volcanic forcing both influenced the latitudinal migration of the tropical belt over the past 800 years according to an analysis of tree ring widths in the northern hemisphere

new insight into a subduction related orogen a reappraisal of the geotectonic framework and evolution of the japanese islands abstract the geotectonic framework and the evolutionary history of the japanese islands need revision in accordance with the various geophysical geological evidence gathered by new methodologies in the recent years including seismic tomography vibroseis ground breaking seismic experiments and detrital zircon chronology these investigations have addressed various themes such as 1 seismic profile of the crust and mantle beneath the japanese islands 2 high precision ages of the protoliths of high p t metamorphic rocks and 3 provenance of terrigenous clastics the results have led to a number of important findings including 1 detection of a large mass of slab around the mantle boundary layer suggesting the long term oceanic subduction beneath japan 2 confirmation of the subhorizontal piled nappe structure for the entire crust of japan 3 finding a new high p t metamorphosed accretionary complex unit that represents the youngest blueschist in japan 4 finding of the oldest early cambrian arc batholith and cover sediments and 5 the identification of plural arc batholiths which have already been erased from the surface based on a synthesis of these new data this article presents a re evaluation of the conventional geotectonic subdivision of the subduction related orogen in japan re definition of the elements and their mutual boundaries and re consideration of the geotectonic evolution of the japanese islands in particular the historical change in provenance suggests that proto japan has experienced large scale tectonic erosion in multiple stages and the corresponding large amounts of continental crust materials were subducted for understanding the orogenic growth of japan during the last ca 500 million years the significance of tectonic erosion coupled with continental contraction as well as the oceanward accretionary growth requires further attention

triangulation of sprites associated halos and their possible relation to causative lightning and micrometeors sprite halos were recently identified as an impulsive but spatially diffuse phenomenon that sometimes occurs just prior to but distinct from sprites the lack of discernible spatial structure and the temporal development sequence in halos differs markedly from the highly structured bodies and tendrils and the complex development sequences of sprites however both phenomena are thought to result from an electric field due to charge moment changes usually associated with large positive cloud to ground cg lightning but also following negative cg flashes three dimensional triangulations of sprites and sprite halos were made between stations in south dakota and wyoming in august 1999 during the nasa sprites99 balloon campaign halos were found to have a gaussian 1 e diameter of 66 km and 1 e thickness of 4 km comparison with the location of the underlying lightning strokes as recorded by the national lightning detection network nldn confirms that the horizontal position of sprites may be laterally offset by as much as 50 km from the underlying parent lightning discharge as has been previously reported the point of maximum apparent brightness for sprite halos occurs at an altitude of 78 km similar to that of sprites however unlike sprites this point tends to be centered directly above the underlying parent lightning discharge 4 6 2 7 km mean distance from the center of the halo to the nldn location this difference in spatial location relative to the underlying lightning suggests that the electrical breakdown associated with discrete sprites may require a random ionizing event such as a micrometeor in contrast sprite halos do not appear to require such a random component

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

chronology of sanbagawa metamorphism by collating age data based on the fossil age of the protoliths radiometric dating of the metamorphic minerals and sedimentary records of erosion at the earth s surface the history of the sanbagawa metamorphism can be summarized as follows 1 the pre metamorphic sedimentary rocks carboniferous jurassic early cretaceous became mixed and formed a thickened packet in the vicinity of an ancient trench through a variety of subduction related tectono sedimentary processes probably in early cretaceous time c 130 120 ma 2 the subducted protoliths underwent progressive metamorphism reaching a maximum depth of c 30 km in late early cretaceous time c 116 10 ma 3 the high p t metamorphic rocks began to rise toward the surface during the interval 110 50 ma with minimum estimates for the average cooling rate around 9 12 c ma and an average uplift rate around 0 4 0 5 mm year 4 finally at some stage after reaching the erosional surface the high p t metamorphic rocks were covered unconformably by the middle eocene c 50 42 ma kuma group on the basis of the present chronological summary of the sanbagawa metamorphism the areal extent of the sanbagawa metamorphism is also discussed with respect to the weakly metamorphosed subduction accretion complex of the next tectonic belt to the south the northern chichibu belt

time and space correlation between sprites and their parent lightning flashes for a thunderstorm observed during the hymex campaign during the night of 22 23 october 2012 together with the hydrology cycle in the mediterranean experiment hymex special observation period 1 campaign optical observations of sprite events were performed above a leading stratiform mesoscale convective system in southeastern france the total lightning activity of the storm was monitored in three dimensions with the hymex lightning mapping array broadband extremely low frequency very low frequency records and radar observations allowed characterizing the flashes and the regions of the cloud where they propagated twelve sprite events occurred over the stratiform region during the last third of the lightning activity period and well after the coldest satellite based cloud top temperature 62 c and the maximum total lightning flash rate 11 min 1 the sprite producing positive cloud to ground sp cg strokes exhibit peak current from 14 to 247 ka charge moment changes cmc from 625 to 3086 c km and impulsive cmc icmc between 242 and 1525 c km the cg flashes that do not trigger sprites are initiated outside the main convective core have much lower cmc values and in average shorter durations lower peak currents and shorter distances of propagation the cmc appears to be the best sprite predictor the delay between the parent stroke and the sprite allows classifying the events as short delayed 20 ms all long delayed sprites i e most of the time carrot sprites are produced by sp cg strokes with low icmc values all sp cg flashes initiate close to the convective core and generate leaders in opposite directions negative leaders finally propagate toward lower altitudes within the stratiform region that coincides with the projected location of the sprite elements

shrimp u pb zircon dating of quartz bearing eclogite from the sanbagawa belt south west japan implications for metamorphic evolution of subducted protolith in order to decipher the origin of eclogite in the high p t sanbagawa metamorphic belt shrimp u pb ages of zircons from quartz bearing eclogite and associated quartz rich rock metasandstone were determined one zircon core of the quartz rich rock yields an extremely old provenance age of 1899 79 ma suggesting that the core is of detrital origin eight other core ages are in the 148 134 ma range and are older than the estimated age for trench sedimentation as indicated by the youngest radiolarian fossil age of 139 135 ma from the sanbagawa schists ages of metamorphic zircon rims 132 112 ma from the quartz rich rock are consistent with metamorphic zircon ages from the quartz bearing eclogite indicating that eclogite facies metamorphism peaked at 120 110 ma these new data are consistent with both the iratsu eclogite body and surrounding highest grade sanbagawa schists undergoing coeval subduction zone metamorphism and subsequent re equilibration under epidote amphibolite facies conditions during exhumation

characteristics of upward lightning on the beijing 325 m meteorology tower and corresponding thunderstorm conditions comprehensive observation on lightning striking the 325 m meteorology tower has been conducted in beijing china during the summer season from 2012 to 2016 for the 20 tower flashes captured by high speed video camera 19 95 cases were initiated from the tower termed as upward lightning ul with duration of 42 844 ms most uls 84 2 16 19 were triggered by nearby lightning of which positive cloud to ground flashes cgs account for 87 5 14 16 analysis on the characteristics of the causal or triggering lightning flashes suggests that the approaching of negative leader process through in cloud horizontal channel is the vital condition for the initiation of upward leader generally the ul initiation follows the nearby discharges while for a special case in our data set the nearby positive return stroke was found to occur after the establishment of an upward channel from the tower it is worth noting that this cg led to a significant enhancement of the tower initiating leader with eight subsequent return strokes and two m component processes occurring to the tower thereafter the radar echo of the corresponding thunderstorm indicates that the other triggered ul otul tended to occur at the dissipation stage of the thunderstorm with relatively low cloud top height and weak radar echo while the self initiating ul siul was more likely to occur when the thunderstorm was in the mature stage and the tower was underneath the stratiform clouds behind the convective region the meteorology condition for siul involved lower ambient temperature and higher wind speed as compared to the otul

vhf radio pictures of lightning flashes to ground we present information obtained from vhf radio pictures of 47 lightning flashes that struck ground 1430 m above mean sea level msl to the north of johannesburg over a period of 16 years radio pictures were obtained using a hyperbolic method i e by taking differences between times at which radio noise from lightning arrived at five widely spaced stations these data were supplemented by recordings of electric field change we found that stepped leaders and intracloud streamers emitted pulses and progressed at speeds that averaged 1 6 105 ms 1 stepped leaders ranged in length from 3 to 13 km bil breakdown intermediate leader waveforms of electric field change were caused by stepped leaders whose branched channels followed complicated paths the electric field changes they recorded in an effective bandwidth of 3 5 khz could be reproduced faithfully by calculations based on an assumption that the radio sources became charged at the expense of a region near the origin of each leader some return strokes radiated trains of noise called q noise whose sources extended at speeds near 108 ms 1 sources of this q noise retraced leader channels before extending them at these high speeds interstroke processes radiated q noise whose sources extended at speeds that averaged 8 7 107 ms 1 most q sources 98 were directed vertically but they pervaded regions that retrogressed at speeds that averaged 2 2 104 ms 1 in directions away from the starting points of the flashes this retrogression was directed horizontally but the vertical q streamers caused j changes to have positive or negative slopes according to the relative positions of q sources and the reversal cone sixty percent of our sample of ground flashes were endowed with portions that were cloud flashes or were themselves minor components of cloud flashes a more detailed summary appears at the end of the paper

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

comparison of seismic attenuation models using zero offset vertical seismic profiling vsp data for seismic frequencies it is common to use an empirical equation to model attenuation usually the attenuation coefficient is modeled with linear frequency dependence a model referred to as the kolsky futterman model other models have been suggested in the geophysical literature we compare eight of these models on a zero offset vertical seismic profiling vsp data set the kolsky futterman the power law the kjartansson the muller the azimi second the azimi third the cole cole and the standard linear solid sls models for three separate depth zones we estimate velocities and q values for all eight models a least squares model fitting algorithm gives almost the same normalized misfit for all models thus none of the models can be preferred or rejected based on the given data set slightly better overall results are obtained for the kolsky futterman model for one depth zone the sls model gave the best result

coordinated analysis of delayed sprites with high speed images and remote electromagnetic fields 1 simultaneous measurements of high altitude optical emissions and magnetic fields produced by sprite associated lightning discharges enable a close examination of the link between low altitude lightning processes and high altitude sprite processes we report results of the coordinated analysis of high speed sprite video and wideband magnetic field measurements recorded simultaneously at yucca ridge field station and duke university from june to august 2005 sprites were detected following 67 lightning strokes all of which had positive polarity our data showed that 46 of the 83 discrete sprite events in these sequences initiated more than 10 ms after the lightning return stroke and we focus on these delayed sprites in this work all delayed sprites were preceded by continuing current moments that averaged at least 11 ka km between the return stroke and sprites the total lightning charge moment change at sprite initiation varied from 600 to 18 600 c km and the minimum value to initiate long delayed sprites ranged from 600 for 15 ms delay to 2000 c km for more than 120 ms delay we numerically simulated electric fields at altitudes above these lightning discharges and found that the maximum normalized electric fields are essentially the same as fields that produce short delayed sprites both estimated and simulation predicted sprite initiation altitudes indicate that long delayed sprites generally initiate around 5 km lower than short delayed sprites the simulation results also reveal that slow 5 20 ms intensifications in continuing current can play a major role in initiating delayed sprites

lightning location relative to storm structure in a leading line trailing stratiform mesoscale convective system 1 horizontal and line normal vertical cross sections and composite images of dallas fort worth lightning detection and ranging ldar ii vhf radiation sources and radar reflectivity over a 30 min period provide a unique perspective on lightning pathways within a leading line trailing stratiform llts mesoscale convective system mcs on 16 june 2002 the overwhelming majority of vhf lightning sources occurred within the leading convective line in a bimodal pattern in the vertical assuming that vhf source density maxima were most likely associated with positive charge then the ldar ii observations suggest that the gross charge structure of the convective region of the mcs was characterized by a tripole with net positive charge centered at 4 5 km agl 3 c and 9 5 km agl 35 c and net negative charge centered roughly in the relative minimum of the vhf source density maximum at 7 km agl 17 c a persistent lightning pathway and inferred positive charge zone sloped rearward by 40 50 km and downward by 4 5 km from the upper vhf source maximum in the convective line through the transition zone and into the radar bright band of the stratiform region in the stratiform region vhf lightning sources and inferred positive charge were concentrated in three layers centered at 4 5 6 and 9 km agl 2 c 11 c and 31 c respectively consistent with past electric field studies of symmetric llts mcss positive cloud to ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation where they were horizontally extensive layered and highly branched the sloping lightning pathway was identical to hypothetical trajectories taken by snow particles these observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line