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

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

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

transionospheric attenuation of 100 khz radio waves inferred from satellite and ground based observations 1 around fifty loran long range navigation transmitters in the northern hemisphere currently launch continuously pulsed 100 khz radio waves into the earth s atmosphere for marine navigation it is discovered that the 100 khz radio waves from the loran transmissions can be detected by the demeter satellite at an altitude of 660 km above the transmitters these novel electric field measurements in space enable the determination of the nocturnal transionospheric attenuation by comparison with ground based electric field measurements the electric field measurements on the satellite indicate that the nocturnal transionospheric attenuation of 100 khz radio waves from loran transmissions is equivalent to a nocturnal subionospheric attenuation of the 100 khz radio waves at a distance of 7 9 mm the radio waves exhibit an average subionospheric attenuation of 5 db mm and it is concluded that the nocturnal transionospheric attenuation of 100 khz radio waves is 35 45 db this result enables future space missions to quantify the intensity of lightning discharges associated with transient luminous events and terrestrial ray flashes

a global analysis of austral summer ocean wave variability during sam enso phase combinations anticipating and mitigating wave related hazards rely heavily on understanding wave variability drivers here we describe wave conditions related to concurrent southern annular mode sam and el nino southern oscillation enso phases during the austral summer to identify such conditions significant wave height hs and peak wave period tp daily anomalies were composited during different sam enso phase combinations over the last four decades 1979 2018 surface wind anomalies were also composited to assist in the interpretation of wave conditions the composites show significant wave variability across all ocean basins and in several semi enclosed seas throughout the different sam enso phase combinations the southern indian and pacific oceans generally experience the strongest tp anomalies during combinations of sam phases with el nino and the weakest tp anomalies during combinations of sam phases with la nina the anomalously large waves observed in the south western pacific tasman sea and the southern ocean previously ascribed to enso conditions seem to be instead associated with the sam variability sam related atmospheric conditions are found to be able to modulate the intensity of enso related winds over the south china sea which in turn alter the magnitude of waves in that region these and other wave anomaly structures described here especially those contrasting the behaviour expected for a given enso phase such as the one found along the california coast stress the importance of understanding relationships between wave parameters and climate patterns interactions

lightning induced brightening in the airglow layer this report describes a transient luminosity observed at the altitude of the airglow layer about 95 km in coincidence with a lightning flash in a tropical oceanic thunderstorm directly beneath it this event provides new evidence of direct coupling between lightning and ionospheric events this luminous event in the ionosphere was the only one of its kind observed during an examination of several thousand images of lightning recorded under suitable viewing conditions with space shuttle cameras several possible mechanisms and interpretations are discussed briefly

an improved elf vlf method for globally geolocating sprite producing lightning 1 the majority of sprites the most common of transient luminous events tles in the upper atmosphere are associated with a sub class of positive cloud to ground lightning flashes cgs whose characteristics are slowly being revealed these cgs produce extremely low frequency elf and very low frequency vlf radiation detectable at great distances from the parent thunderstorm during the steps field program in the united states elf vlf transients associated with sprites were detected in the negev desert israel some 11 000 km away within a two hour period on 4 july 2000 all of the sprites detected optically in the united states produced detectable elf vlf transients in israel all of these transients were of positive polarity representing positive lightning using the vlf data to obtain the azimuth of the transients and the elf data to calculate the distance between the source and receiver we remotely determined the position of the sprite forming lightning with an average locational error of 184 km error of 1 6

dancing sprites detailed analysis of two case studies on 29 30 october 2013 a low light video camera installed at pic du midi 2877 m recorded transient luminous events above a very active storm over the mediterranean sea the minimum cloud top temperature reached 73 c while its cloud to ground cg flash rate exceeded 30 fl min 1 some sprite events have long duration and resemble to dancing sprites we analyze in detail the temporal evolution and estimated location of two series of sprite sequences as well as the cloud structure the lightning activity the electric field radiated in a broad range of low frequencies and the current moment waveform of the lightning strokes i in each series successive sprite sequences reflect time and location of corresponding positive lightning strokes across the stratiform region ii the longer time delayed 20 ms sprite elements correspond to the lower impulsive charge moment changes icmc of the parent strokes 200 c km and they are shifted few tens of kilometers from their sp cg stroke however both short and long time delayed sprite elements also occur after strokes that produce a large icmc and that are followed by a continuing current iii the long time delayed sprite elements during the continuing current correspond to surges in the current moment waveform they occur sometimes at an altitude apparently lower than the previous short time delayed sprite elements possibly because of changes in the local conductivity iv the largest and brightest sprite elements produce significant current signatures visible when their delay is not too short 3 5 ms

horizontal distribution of electrical and meteorological conditions across the stratiform region of a mesoscale convective system abstract five soundings of the electric field and thermodynamic properties were made in a mesoscale convective system mcs that occurred in oklahoma and texas on 2 3 june 1991 airborne doppler radar data were obtained from three passes through the stratiform echo from these electrical kinematical and reflectivity measurements a conceptual model of the electrical structure of an mcs is developed low level reflectivity data from the storm s mature and dissipating stages show typical mcs characteristics the leading convective region is convex forward and the back edge of the stratiform echo is notched inward the maximum areal extent of the low level echo is about 250 km 550 km and the radar bright band is intense reflectivity 45 50 dbz through an area of at least 50 km 100 km the reflectivity above the bright band is horizontally stratified with decreasing intensity and echo top height toward the rear of the system analyses of the velocity data reveal a convective line relative flow struct

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

sprite initiation altitude measured by triangulation 1 high time resolution 10 000 frames per second images of sprites combined with multistation concurrent video recordings have provided data for triangulation of the altitude of the initial sprite onset the high speed images were obtained from the langmuir laboratory new mexico during summer campaigns in 2007 and 2008 with video observations from sites at portales new mexico and las vegas new mexico sprites start with one or more downward propagating streamer heads the triangulated onset altitudes of this initial downward streamer vary between 66 and 89 km in some sprites the downward streamers are followed a little later by upward propagating streamers the upward streamers start from a lower altitude and existing luminous sprite structures and their triangulated altitudes vary from 64 to 78 km the downward streamers create c sprite characteristics while the upward streamers form the broad diffuse tops of carrot sprites in the sprites analyzed the higher onset altitudes for the downward propagating initial streamers were associated with c sprites and the lower with carrot sprites but our larger data set indicates that this is not generally the case it appears that the dominant sprite types vary from year to year indicating that some longer lasting environmental parameter such as mesospheric conductivity and composition or thunderstorm cloud dynamics may play an important role in determining the types of sprites observed

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

global distributions and occurrence rates of transient luminous events 1 we report the global transient luminous event tle distributions and rates based on the imager of sprites and upper atmospheric lightning isual experiment onboard the formosat 2 satellite isual observations cover 45 s to 25 n latitude during the northern summer and 25 s to 45 n latitude during the northern winter from july 2004 to june 2007 isual recorded 5 434 elves 633 sprites 657 halos and 13 gigantic jets surprisingly elve is the dominant type of tles while sprites halos are a distant second elve occurrence rate jumps as the sea surface temperature exceeds 26 degrees celsius manifesting an ocean atmosphere ionosphere coupling in the isual survey elves concentrate over the caribbean sea south china sea east indian ocean central pacific ocean west atlantic ocean and southwest pacific ocean while sprites congregate over central africa japan sea and west atlantic ocean the isual experiment observed global rates of 3 23 0 50 0 39 and 0 01 events per minute for elves sprites halos and gigantic jets respectively taking the instrumental detection sensitivity and the restricted survey area into account the corrected global occurrence rates for sprites and elves likely are a factor of two and an order of magnitude higher respectively isual observations also indicate that the relative frequency of high peak current lightning 80 ka is 10 times higher over the oceans than over the land on the basis of the corrected isual elve global occurrence rate the total electron content at the lower ionosphere above elve hot zones was computed to be elevated by more than 5

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

new observations of sprites from the space shuttle 1 we present the results of space based observations of sprites obtained during the mediterranean israeli dust experiment meidex sprite campaign conducted on board the space shuttle columbia during its sts 107 mission in january 2003 a total of 6 hours of useful data were saved from 21 different orbits of which 1 5 contained lightning we imaged sprites from an altitude of 280 km using a calibrated multispectral camera above thunderstorms in various geographical locations mainly in central africa northern australia and south america and also over the pacific and indian oceans in this paper we report on sprites observed from ranges 1600 2000 km from the shuttle at altitudes of 40 90 km above the ground their brightness was in the range of 0 3 1 7 mega rayleighs mr in the 665 nm filter and 1 44 1 7 mr in the 860 nm filter on the basis of the frequency of observed events and the number of tropical thunderstorms we estimate the sprite rate in the tropics to be of the order of several per minute

the cloud ionosphere discharge a newly observed thunderstorm phenomenon this paper deals with a luminous electric discharge that forms in the mesospheric region between thundercloud tops and the ionosphere at 90 km altitude these cloud ionosphere discharges cis following visual reports dating back to the 19th century were finally imaged by a low light tv camera as part of the skyflash program at the university of minnesota in 1989 many observations were made by various groups in the period 1993 1996 the characteristics of cis are that they have a wide range of sizes from a few kilometers up to 50 km horizontally they extend from 40 km to nearly 90 km vertically with an intense region near 60 70 km and streamers extending down toward cloud tops the cis are partly or entirely composed of vertical luminous filaments of kilometer size the predominate color is red the tv images show that the cis usually have a duration less than one tv field 16 7 ms but higher speed photometric measurements show that they last about 3 ms and are delayed 3 ms after an initiating cloud ground lightning stroke 95 of these initiating strokes are found to be positive i e carry positive charges from clouds to ground the preference for positive initiating strokes is not understood theories of the formation of cis are briefly reviewed

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

altitude time development of sprites 1 data from sprites using a 16 channel multi anode photometer map have been recorded at 0 1 ms resolution the majority of the sprites have onsets at an altitude of 70 75 km and subsequently propagate both upward and downward from this initial altitude the statistical lifetime of the emissions measured by the blue sensitive map is approximately 1 3 ms the velocities of propagation are between 107 and 108m s 1 with larger velocities being measured at higher altitudes the larger propagation velocities of the upward and downward sprite luminosity channels are consistent with the characteristics of highly over voltage streamers in the mesosphere

gigantic jets between a thundercloud and the ionosphere transient luminous events in the atmosphere such as lighting induced sprites and upwardly discharging blue jets were discovered recently in the region between thunderclouds and the ionosphere in the conventional picture the main components of earth s global electric circuit include thunderstorms the conducting ionosphere the downward fair weather currents and the conducting earth thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere where the electric potential is hundreds of kilovolts higher than earth s surface it has not been clear however whether all the important components of the global circuit have even been identified here we report observations of five gigantic jets that establish a direct link between a thundercloud altitude approximately 16 km and the ionosphere at 90 km elevation extremely low frequency radio waves in four events were detected while no cloud to ground lightning was observed to trigger these events our result indicates that the extremely low frequency waves were generated by negative cloud to ionosphere discharges which would reduce the electrical potential between ionosphere and ground therefore the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites

transient airglow enhancements observed from the space shuttle columbia during the meidex sprite campaign 1 first results of observations of elves during the last mission of the space shuttle columbia by the meidex mediterranean israeli dust experiment instrument are reported during the eclipse parts of 25 orbits there were observations toward the earth s limb above the areas of active thunderstorms strong enhancements of the brightness of the airglow layer above lightning flashes were observed with lateral dimensions exceeding 400 km this phenomenon known as elves is a clear manifestation of the interaction between the electromagnetic pulse from the lightning stroke and the lower ionosphere the observed elves have been produced both by vertical and horizontal discharges

elves lightning induced transient luminous events in the lower ionosphere observations of optical phenomena at high alti tude a bove thunderstorms using a multichannel high speed photometer and image intensified ccd cameras were carried out at yucca ridge field station 40040 n 104o 56 w colorado as part of the sprites 95 campaign from 15 june to august 6 1995 these newneasurements indicate that diffuse optical flashes with a duration of i ms and a hori zontal scale of 100 300 km occur at 75 105 km altitude in the lower ionosphere just after the onset of cloud to ground lightning discharges but preceding the onset of sprites here we designate these events as alves to distinguish them from i ed sprites this finding is consistent with the production of diffuse optical emissions due to the heating of the lower ionosphere by electromagnetic pulses generated by lightning discharges as suggested by several authors

palaeomagnetism of some cenozoic sediments cairo fayum area egypt abstract the palaeomagnetic and rock magnetic characteristics of some cenozoic rocks from the cairo fayum area have been investigated a total number of 259 oriented core samples were collected at 32 sites located in rocks of eocene 13 sites oligocene 11 sites and pliocene 9 sites ages most of these rocks carry a weak but stable remanent magnetisation that is principally carried by hematite goethite and magnetite are also found in some samples as subordinate constituents careful thermal demagnetisation successfully enabled the isolation of the characteristic remanent magnetisation normal and reversed polarities that passed a reversal test have been recorded in the three age groups this magnetisation is probably of primary origin and reflects the ages of the rocks the resultant palaeomagnetic poles are considered reliable and represent a good contribution to the african palaeomagnetic database and should help in further refining of the cenozoic apwp for africa

vlf signatures of ionospheric disturbances associated with sprites vlf perturbations on signals propagating along great circle paths gcp through electrically active midwest thunderstorms are associated with luminous high altitude glows referred to as sprites observed from aircraft or ground the data constitutes the first evidence that the physical processes leading to sprites also alter the conductivity of the lower ionosphere

low light video observations of frequent luminous structures in the stratosphere above thunderstorms a new series of video measurements were made of the phenomenon provisionally termed the cloud to stratosphere cs event an electrical discharge extending to great heights above thunderstorm tops this new series of measurements were accomplished by properly positioning a sensor the xybion model iss 225 low light monochrome imaging system with a c mount fl 8 manual zoom lens and training it on the appropriate portion of the sky above a distant thunderstorm complex mean fort collins colorado the resulting images are currently undergoing intensive analysis some tentative conclusions are given cloud to stratosphere events occur far more frequently than previously suspected and are perhaps a ubiquitous aspect of many larger convective systems cloud to stratosphere events are also of substantial horizontal extent on the order of tens of kilometers in some cases

ground based detection of sprites and their parent lightning flashes over africa during the 2006 amma campaign sprites have been detected in video camera observations from niger over mesoscale convective systems in nigeria during the 2006 amma african monsoon multidisciplinary analysis campaign the parent lightning flashes have been detected by multiple extremely low frequency elf receiving stations worldwide the recorded charge moments of the parent lightning flashes are often in excellent agreement between different receiving sites and are furthermore consistent with conventional dielectric breakdown in the mesosphere as the origin of the sprites analysis of the polarization of the horizontal magnetic field at the distant receivers provides evidence that the departure from linear magnetic polarization at elf is caused primarily by the day night asymmetry of the earth ionosphere cavity copyright c 2009 royal meteorological society

sprite observations in the northern territory of australia sprites a form of brief luminous discharge in the upper atmosphere above a thunderstorm were observed and imaged on two video cameras in australia s northern territory these were the first such ground based observations made outside the united states sprite discharges typically took place between the altitudes of 50 km and 80 km and spanned an average width of 44 km many of the sprite events were of long duration with an average of 145 ms these spatial and temporal features were similar to those observed from the ground and the air in the united states during the longer events some luminous discharge elements were observed to decay as other new elements formed as the new elements were often laterally displaced from the old the sprites sometimes appeared to dance across the sky this phenomenon has been observed in colorado and named dancing sprites the lateral progression of sprite elements observed in the northern territory was overwhelmingly in one direction and covered distances of up to 90 km

structured elves modulation by convectively generated gravity waves we report on a markedly striated elve emissions of light and very low frequency perturbations due to electromagnetic pulse source a tiger elve observed using an intensified high speed phantom camera system at the yucca ridge field station near fort collins colorado on the night of 12 june 2013 this elve was induced by a 204 ka positive cloud to ground lightning flash within a mesoscale convective system in western south dakota a halo and a sprite followed the elve the banded structure in the elve was aligned with convectively generated gravity waves cggws independently observed by a collocated color near infrared camera assuming the height of the oh layer and elve both to be 85 km photogrammetry allowed projection of the elve and the cggws onto the same geographic map the tiger elve stripes approximately overlay on the troughs dark bands of cggws this is consistent with model predictions that the ionization rate in the d region ionosphere is inversely proportional to the air density which is modulated by the cggws

serial soundings of electric field through a mesoscale convective system five partial balloon soundings of electric field and thermodynamics were made in a mesoscale convective system mcs in 1998 data were gathered in an updraft and outside updrafts within the convective region in the transition zone and in the stratiform cloud region in the first sounding the maximum and average inferred updraft speeds 27 and 15 m s 1 are the largest found to date in soundings through mcs convection as in previous measurements the electric field profile is simpler and fewer charge regions are inferred within the updraft than elsewhere together the first four soundings support in most details a previously published conceptual model of mcs electrical structure from the convective region updraft to the transition zone two exceptions within the soundings were found these involve opposite polarity of the lowest two charge regions in the transition zone cloud and additional complexity above the main negative charge region the earlier conceptual model also showed possible connections between charge regions across an mcs but those were based on soundings through many different mcss the first four soundings presented herein provide stronger evidence for three to five similar charge regions across the front of this mcs the sounding through the stratiform cloud region was atypical and does not fit the conceptual model and no connections to charge regions in the rest of the mcs are obvious two soundings presented from a second mcs indicate that the upper three charge regions in the transition zone are connected to the stratiform cloud as depicted in earlier conceptual models

observations of lightning in convective supercells within tropical storms and hurricanes cloud to ground cg lightning observations from land based lightning detection networks now allow monitoring this component of the electrical structure of tropical storms and hurricanes within a few hundred kilometers of the united states coastline several case studies confirm the long held opinion that lightning is rather common within the outer rainbands the general absence of cg lightning within the interior of mature tropical cyclones is also apparent on the other hand bursts of cg lightning near the circulation center of developing storms appear to precede periods of further deepening the cg events are associated with convective supercells whose anvil canopies can often obscure much of the underlying storm near eyewall cg bursts preceding periods of intensification were noted in hurricanes diana 1984 and florence 1988 a detailed case study of the 1987 unnamed tropical storm that struck the texas louisiana coastline reveals that lightning was associated with two large supercells these supercells appeared to be the trigger for the development of a closed circulation that formed several hours after the apparent low pressure center made landfall further studies of lightning may provide additional insight into the role of convective supercells in tropical storm intensification it may also provide a useful diagnostic of impending deepening

is there a unique signature in the ulf response to sprite associated lightning flashes 1 using observations made by the finnish chain of pulsation magnetometers we select typical properties of the ulf response to sprite associated lightning events taken from the eurosprite 2003 summer campaign we concentrate on frequencies below the schumann resonance and compare the obtained results with properties obtained from positive cloud to ground lightning discharges which are not associated with sprites the latter we take from listings of the meteorage lightning detection network which correlate with strong impulsive events seen in the finnish chain the evidence shows no unique and identifiable ulf signature relating to the sprite causative discharges

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

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

an unusual sequence of sprites followed by a secondary tle an analysis of elf radio measurements and optical observations we present an extraordinary case of sprites in rapid succession four sprite clusters in only 400 ms followed by a secondary jet simultaneous elf and optical observations as well as lightning data enabled us to thoroughly document this unique event locations of the transient luminous events tles were triangulated using video recordings from nydek czech republic and sopron hungary we found that sprites were displaced up to 70 km from their parent lightning the current moment waveform and charge moment changes associated with the event were reconstructed from the elf electromagnetic signature recorded at the hylaty station poland by a new method the results suggest that both a short delayed and a long delayed sprite were generated by a single positive cloud to ground discharge that had an intense continuing current it had an unusual progression and lasted 200 ms a large increase in the current moment during the development of a massive carrot sprite provides evidence in favor of sprite current our results also support the formation of an electric environment hypothesized to be necessary for the generation of the secondary tles

rare measurements of a sprite with halo event driven by a negative lightning discharge over argentina 1 as part of a collaborative campaign to investigate transient luminous events tles over south america coordinated optical elf vlf and lightning measurements were made of a mesoscale thunderstorm observed on february 22 23 2006 over northern argentina that produced 445 tles within a 6 hour period here we report comprehensive measurements of one of these events a sprite with halo that was unambiguously associated with a large negative cloud to ground cg lightning discharge with an impulsive vertical charge moment change mqv of 503 c km this event was similar in its location morphology and duration to other positive tles observed from this storm however the downward extent of the negative streamers was limited to 25 km and their apparent brightness was lower than that of a comparable positive event observations of negative cg events are rare and these measurements provide further evidence that sprites can be driven by upward as well as downward electric fields as predicted by the conventional breakdown mechanism

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

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

meteorological and electrical aspects of several winter thunderstorms with sprites in the hokuriku area of japan 1 vhf lf and elf lightning events thunderstorms and surface electric fields related to sprites were observed simultaneously during the winter of 2004 2005 in hokuriku japan the analysis of these observations enables us to investigate the relationship among sprites lightning characteristics and thunderstorm structure just before sprite genesis typical winter sprite parent thunderstorms had a mesoscale cloud area with small embedded convective cells positive charges responsible for sprites tend to reside in the upper part of the thunderstorms only a few positive charges were assumed to be located in the lower part the total amount of positive charges removed by a sprite producing flash from the upper and lower parts of the thunderstorms were estimated to be approximately 100 c and as large as 300 400 c respectively active thunderstorms with lightning accompanied by transient currents tended to generate simple sprites more complex sprites were excited by lightning with continuing currents which were generated by a few active thunderstorms and thunderstorms with precipitating stratiform clouds vhf sources related to sprites can be found in the range of 5 to 72 km the range of displacement between a sprite element and the corresponding positive cloud to ground lightning discharge or the first vhf source was 6 30 km and the bottom of the sprite bodies was located between 66 and 74 km on the basis of these results we deduced that the complexity of sprite morphology might be attributed to the differences in lightning characteristics

electrical structure and updraft speeds in thunderstorms over the southern great plains we have acquired 11 balloon soundings of the electric field and thermodynamics in large and sometimes severe and tornadic thunderstorms over the southern great plains the ascent rates of the balloons were used to divide the soundings into weak and strong updrafts all 11 soundings had magnitudes of charge densities and thicknesses of charge regions similar to those reported previously in small thunderstorms the five weak updraft soundings had complex charge structures of 7 9 charge regions below 10 km altitude the magnitude of the maximum measured electric field in these soundings was 100 150 k v m 1 the four soundings in strong updrafts had balloon ascent rates of at least 15 m s 1 for at least 1 km these soundings had simpler electrical structures of 3 5 charge regions below 10 km altitude their maximum measured electric fields ranged from 85 to 130 kv m 1 the data may support an earlier hypothesis that charge is elevated in strong updrafts in addition the data may suggest that simpler charge structures are associated with proximity to strong updrafts rather than with different storm types

characteristics of luminous structures in the stratosphere above thunderstorms as imaged by low light video an experiment was conducted in which an image intensified low light video camera systematically monitored the stratosphere above distant 100 800 km mesoscale convective systems over the high plains of the central u s for 21 nights between 6 july and 27 august 1993 complex luminous structures were observed above large thunderstorm clusters on eleven nights with one storm system 7 july 1993 yielding 248 events in 410 minutes their duration ranged from 33 to 283 ms with an average of 98 ms the luminous structures generally not visible to the naked dark adapted eye exhibited on video a wide variety of brightness levels and shapes including streaks aurora like curtains smudges fountains and jets the structures were often more than 10 km wide and their upper portions extended to above 50 km msl

some characteristics of cloud to ground lightning in tropical northern australia peak currents and polarities for the first return strokes of approximately 5000 cloud to ground lightning flashes have been studied the flashes were associated with eight mesoscale convective systems mcss that occurred in tropical northern australia in 1989 during the second field phase of the down under doppler and electricity experiment dundee statistical analysis of the lightning data produced an average peak current independent of polarity of 39 ka when considered with the average cloud top heights of the tropical mcss examined herein the 39 ka peak current average appears to be in general agreement with orville s 1990 hypothesis of latitudinal variation in peak current in six of the dundee mcss consisting of both convective and stratiform precipitation components we found that positive peak current maxima tended to occur in the trailing stratiform region while positive peak current minima were generally situated in convective precipitation we also observed this pattern in a middle latitude mcs that occurred on june 10 11 1985 the magnitude of the positive peak current maxima in the tropical mcss and the middle latitude mcs increased coincidentally in time with the growth of the stratiform regions and reached peak values when the stratiform regions were most intense given the apparent dependence of positive peak current magnitude on the life cycle of the stratiform region and the spatial separation between positive peak current maxima and the convective line we offer further support for a noninductive charging mechanism being responsible for the electrical charging and subsequent lightning observed in the trailing stratiform regions of mcss

how do winter thundercloud systems generate sprite inducing lightning in the hokuriku area of japan 1 lightning and thundercloud systems leading to the generation of sprites were examined on the basis of analyses on the interrelation among radar reflectivity lightning and static electric field during the winter of 2004 2005 in the hokuriku area of japan eleven cases from the observed fifteen sprite events exhibit similar characteristics so we present a typical case study of the thundercloud system the analysis results are summarized as follows 1 the sprite inducing cg was triggered by a cloud flash produced by an active cell 2 the sprite inducing cg removed large positive charge from the stratiform region of another thunderstorm cell by the long linear lightning channel 3 the origin of sprite inducing large positive charge appears to be located in the stratiform region

electrical discharge from a thundercloud top to the lower ionosphere for over a century numerous undocumented reports have appeared about unusual large scale luminous phenomena above thunderclouds1 2 3 4 5 6 and more than 80 years ago it was suggested that an electrical discharge could bridge the gap between a thundercloud and the upper atmosphere7 8 since then two classes of vertically extensive optical flashes above thunderclouds have been identified sprites9 10 11 and blue jets12 13 14 sprites initiate near the base of the ionosphere develop very rapidly downwards at speeds which can exceed 107 m s 1 ref 15 and assume many different geometrical forms16 17 18 19 in contrast blue jets develop upwards from cloud tops at speeds of the order of 105 m s 1 and are characterized by a blue conical shape12 13 14 but no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a thundercloud and the lower ionosphere here we report a video recording of a blue jet propagating upwards from a thundercloud to an altitude of about 70 km taken at the arecibo observatory puerto rico above an altitude of 42 km normally the upper limit for blue jets and the lower terminal altitude for sprites the flash exhibited some features normally observed in sprites as we observed this phenomenon above a relatively small thunderstorm cell we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit

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

positive charge in the stratiform cloud of a mesoscale convective system a balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in cloud positive charge regions these charge regions are located at altitudes of 5 1 5 6 km and 6 4 6 8 km above the level of 0 c at 4 2 km the two positive charge regions are the likely sources of six positive cloud to ground flashes with large peak currents 32 ka that occurred within 60 km of the balloon during its flight the amount of charge transferred by three of these positive flashes that made q bursts is calculated in the range of 97 196 c flashes of this sort are known to produce sprites and elves in the mesosphere the positive charge regions in this stratiform cloud are substantially lower than the 10 km altitude commonly assumed for the positive charge in many sprite modeling studies

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

observations of lightning in the stratosphere an examination and analysis of video images of lightning captured by the payload bay tv cameras of the space shuttle provided a variety of examples of lightning in the stratosphere above thunderstorms these images were obtained on several recent shuttle flights while conducting the mesoscale lightning experiment mle the images of stratospheric lightning illustrate the variety of filamentary and broad vertical discharges in the stratosphere that may accompany a lightning flash a typical event is imaged as a single or multiple filament extending 30 to 40 km above a thunderstorm that is illuminated by a series of lightning strokes examples are found in temperate and tropical areas over the oceans and over the land

strong electric fields from positive lightning strokes in the stratosphere 1 a balloon payload launched in brazil has measured vector electric fields from lightning at least an order of magnitude larger than previously reported above 30 km in the stratosphere during the flight hundreds of lightning events were recorded including several positive cloud to ground lightning strokes a two stroke flash with small 15 ka peak current and moderate 53 ka positive strokes at a horizontal range of 34 km produced field changes over 140 v m at 34 km altitude on board optical lightning detection recorded with gps timing coupled with ground based lightning location gives high time resolution for study of the electric field transient propagation these measurements imply that lightning electric fields in the mesosphere over large thunderstorms may be much larger than previously measured citation holzworth r h m p mccarthy j n thomas j chin t m chinowsky m j taylor and o pinto jr 2005 strong electric fields from positive lightning strokes in the stratosphere geophys res lett 32 l04809 doi 10 1029 2004gl021554

recent advances in theory of transient luminous events 1 this paper presents an overview of the recent modeling efforts directed to the interpretation of observed features of transient luminous events termed sprites blue jets and gigantic jets the primary emphasis is placed on interpretation of various emissions documented to date from sprites and comparison of exiting models with recent high speed video and satellite based observations of sprites we also discuss the recently advanced theories of blue jet and gigantic jet discharges describing electrodynamic conditions which facilitate escape of conventional lightning leaders from thundercloud tops and their upward propagation toward the ionosphere the paper concludes with a brief survey of the recent literature on chemical and global electric circuit effects of sprite and jet discharges

observations of two sprite producing storms in colorado two sprite producing thunderstorms were observed on 8 and 25 june 2012 in northeastern colorado by a combination of low light cameras a lightning mapping array polarimetric and doppler radars the national lightning detection network and charge moment change measurements the 8 june event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h the majority of sprites occurred during a lull in convective strength as measured by total flash rate flash energy and radar echo volume mean flash area spiked multiple times during this period however total flash rates still exceeded 60 min sup 1 and portions of the storm featured a complex anomalous charge structure with midlevel positive charge near 20degc the storm produced predominantly positive cloud to ground lightning all sprite parent flashes occurred on the northeastern flank of the storm where strong westerly upper level flow was consistent with advection of charged precipitation away from convection providing a pathway for stratiform lightning the 25 june event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h the sprites again occurred during a convective lull with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area however all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud the results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms

cenozoic to cretaceous paleomagnetic dataset from egypt new data review and global analysis abstract different phases of igneous activity took place in egypt during the mesozoic and the cenozoic and oriented samples were collected from three cenozoic localities baharya oasis in the western desert abu had in the eastern desert and quseir along the red sea coast and four cretaceous localities toshki abu simbel south of aswan and shalaten abu shihat along the red sea coast rock magnetic properties of the samples indicate magnetite and titanomagnetite as the main carrier of the remanent magnetization following stepwise demagnetization characteristic remanent directions were identified only for 62 of the samples a fairly low rate for that type of samples and 8 new paleomagnetic poles were calculated all our cenozoic poles fall clearly off master polar wander paths proposed for south africa therefore all paleomagnetic results previously published for egypt were compiled from cretaceous to quaternary the published poles largely overlap blurring the egyptian apparent polar wander path a new analysis at the site level was then carried out only poles having a kappa larger than 50 were selected and new pole positions were calculated by area and by epoch when at least 3 sites were available even though the selection drastically reduced the number of considered poles it allows definition of a reliable cenozoic apparent polar wander trend for egypt that differs from the south african master polar wander path by about 10 15 if the cretaceous igneous poles are in good agreement with the rest of the african data the sedimentary poles plot close to the cenozoic portion of the south african master polar wander path a discrepancy that could be related either to inclination flattening and or error on age and or remagnetization in the cenozoic

on the fine structure of thunderstorms leading to the generation of sprites and elves fractal analysis 1 the fine structure of convective clouds leading to the generation of sprites and elves has been studied using radar images sprites and elves were observed on two days 19 december 1998 and 27 january 1999 in lightning during winter thunderstorms on the sea of japan fractal analyses of the radar images as an ensemble and as separate clusters for those two days have been performed with respect to the occurrence of sprites and elves we have found that a sprite and or an elve is triggered when and just after the image cluster maximum size increases to a certain value 150 km and the ensemble fractal dimension approaches a threshold i e percolation threshold

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

long range lightning geolocation using a vlf radio atmospheric waveform bank 1 lightning discharges generate broadband electromagnetic pulses with a peak component in the very low frequency vlf 3 30 khz range vlf waves propagate through the earth ionosphere waveguide with relatively low attenuation enabling the detection of these radio atmospherics at great distances from the lightning discharge a new technique of long range 6000 km global lightning geolocation via sferic detection is presented this new technique catalogs the dominant variation in expected received waveforms in a set of waveform banks which are then used to estimate the propagation distance and accurately determine the arrival time using three sensors in a trial network this new technique is used to demonstrate a median accuracy of 1 4 km depending on the time of day an overall cloud to ground cg stroke detection efficiency between 40 and 60 is estimated by correlating individual lightning stroke events to data from the national lightning detection network nldn additional events reported by the trial network are shown to have a tight spatial clustering to storm clusters identified by nldn suggesting that many of the unmatched events correspond to weak cloud to ground strokes m components or cloud pulses exploiting an empirical correlation between peak vlf field strength and peak current values reported by nldn we also provide unvalidated estimates of the peak current and lightning channel polarity the trial network does not distinguish between cloud and ground discharges so these peak current estimates only relate to an earth referenced channel current for the subset of reported events that are return strokes

spatial and temporal evolution of horizontally extensive lightning discharges associated with sprite producing positive cloud to ground flashes in northeastern spain 1 during the evening of 6 august 2008 a small mesoscale convective system mcs entered the area of radar and 2 d interferometric lightning detection system coverage in northeastern spain and produced 17 sprites recorded by a camera at only 95 180 km distance this study presents an analysis of the in cloud component of the sprite associated lightning flashes and those of other flashes the analysis focuses on the horizontal development of sprite producing lightning by discussing three examples divided into the periods before the positive cloud to ground flash cg between cg and the end of the sprite and the period after the sprite location and horizontal size of sprites appear to be well explained by the temporal and spatial development of the lightning path the majority of sprite producing discharges started directly at the rear side of developing and mature convective cores within the decaying mcs either with the cg or with preceding negative leaders the cg started a burst of vhf sources during which the sprite developed delayed carrot sprites developed after a secondary smaller burst and were well collocated with the burst toward the rear of the mcs the order of development of elements in a grouped sprite followed the direction of lightning propagation during the burst stage the second part of the analysis concentrates on the metrics of sequences of vhf sources and shows that sprites are indeed produced by the largest longest lasting discharges with particularly large line perpendicular dimensions 37 km median compared with 11 km for cg 25 ka

sprites as evidence of vertical gravity wave structures above mesoscale thunderstorms large area multicell thunderstorms lead to the formation of vertically oriented cylindrical structures of gravity waves at mesospheric altitudes closely resembling those observed in optical emissions associated with transient luminous glows called sprites

large charge moment change lightning on 31 may to 1 june 2013 including the el reno tornadic storm on 31 may 2013 a line of severe tornadic thunderstorms the el reno event developed during the local afternoon in central oklahoma usa within range of the oklahoma lightning mapping array the evolution of the event can be separated into three distinct periods an early period before 02 00 utc on 1 june when the storm consisted of discrete supercells a middle period 02 00 05 00 utc when the convection began merging into a linear feature and stratiform precipitation developed and a late period after 05 00 utc featuring a mature mesoscale convective system mcs each of these periods demonstrated distinct patterns in the large 100 c km charge moment change cmc lightning that was produced during the early period large cmc positive cloud to ground cg lightning was produced in the convective cores of supercells these flashes were small in area typically 500 km2 300 c km in the developing stratiform similar to typical sprite parent lightning in mcss during the late period convective large cmc cgs ceased and instead large cmc negative cgs were produced in and near the mcs convection these flashes neutralized charge both in convection as well as in adjacent stratiform and anvil precipitation the results suggest that the cmc metric has potential applications for studying tropospheric weather

active concomitant counterclockwise rotation and northwards translation of africa during the albian campanian time a paleomagnetic study on the wadi natash alkaline volcanic province 104 78ma south eastern desert egypt abstract africa was a key tectonic unit in the geologic evolution of the tethyan realm in the middle late cretaceous during the rifting of the south equatorial atlantic ocean this research sheds light on the tectonic evolution of africa during the albian campanian time the two end members of the wadi natash alkaline volcanic province wnavp 104 78 ma in the south eastern desert of egypt were studied paleomagnetically the wnavp 24 5 n 34 25 e is made up of a thick succession of differentiated lava flows grading from alkali olivine basalt aob followed by hawaiite mugearite and benmoreite flows with abundant sandstone interbeds all intruded by a large number of trachyte phonolite tr ph circular lava domes and ring dykes forming conspicuous landmarks in the province the oldest flows of the aob 104 7 ma and the youngest tr ph plugs and ring dykes 86 78 ma as well as the interbedded turonian taref sandstone formation previously known as nubian sandstone were sampled all over the province which covers more than 500 km 2 the isothermal remanent magnetization irm study pointed to magnetite family as the major remanence in wadi natash volcanics with little contribution from goethite hematite minerals on the other hand goethite and or hematite are the dominant remanence carriers in the interbedded taref sandstone after the progressive stepwise thermal demagnetization of all samples the characteristic remanence chrm direction for each rock type was visually isolated and its best fit line was calculated followed by the site means rock unit means and the paleomagnetic poles this paleomagnetic study revealed that 1 in the tilt corrected coordinates the mean chrm of the oldest aob flows n 12 sites was dec inc 340 10 k 54 95 6o yielding a north pole at 55 n 250 e the chrm of the youngest tr ph ring dykes and plugs n 10 sites was dec inc 354 3 5 k 60 95 6 3o yielding a north pole at 66 5 n 229 e 2 on the other hand the site mean chrms of the taref sandstone interbeds n 8 sites in the present day in situ coordinates are clustered around the present day geomagnetic field with a mean dec inc 3 33 k 37 95 9 3 yielding a north pole at 83 n 191 e the two paleomagnetic poles of the aob and the tr ph are in accordance with albian campanian poles from africa including madagascar and those rotated from the main cratons such as the north american craton europe including greenland and iberia south america and india using the published plate kinematics and paleomagnetic euler pole pep rotation parameters paleogeographically the two obtained poles of wadi natash volcanics place the african plate at two different azimuths and paleolatitudes during albian cenomaniam and santonian middle campanian tectonically these two paleomagnetic poles point to an active synchronous northwards translation associated with a counterclockwise rotational convergence of africa towards eurasia during the albian campanian time between the time of the aob eruption 104 7 ma and the intrusion of the tr ph 86 78 ma africa concomitantly rotated counterclockwise about 14 and translated northwards towards eurasia about 6 of latitude