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

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

north atlantic subtropical mode waters and ocean memory in hadcm3 abstract a study of the formation and propagation of volume anomalies in north atlantic mode waters is presented based on 100 yr of monthly mean fields taken from the control run of the third hadley centre coupled ocean atmosphere gcm hadcm3 analysis of the temporal and spatial variability in the thickness between pairs of isothermal surfaces bounding the central temperature of the three main north atlantic subtropical mode waters shows that large scale variability in formation occurs over time scales ranging from 5 to 20 yr the largest formation anomalies are associated with a southward shift in the mixed layer isothermal distribution possibly due to changes in the gyre dynamics and or changes in the overlying wind field and air sea heat fluxes the persistence of these anomalies is shown to result from their subduction beneath the winter mixed layer base where they recirculate around the subtropical gyre in the background geostrophic flow anomalies in the warmest mode 18 c formed on the western

charge rearrangement by sprites over a north texas mesoscale convective system 1 charge rearrangement by sprites is analyzed for a mesoscale convective system mcs situated in north texas and east new mexico on 15 july 2010 during the thunderstorm electric field data were recorded by the langmuir electric field array lefa while magnetic field data were recorded by the charge moment network near duke university a high speed 12500 fps video system operated at langmuir laboratory recorded telescopic images of the sprites data from the national lightning detection network nldn show that each sprite was preceded by a series of cloud discharges and cloud to ground discharges the triggering event preceding the sprite was typically a positive cloud to ground cg stroke for one out of the 10 sprites that were recorded there was a positive hump in the electric field a few milliseconds after the cg return stroke the size and shape of the hump roughly matched the light intensity emitted from the sprite the electric field hump is fit by a sprite current that originates in the ionosphere and propagates downward producing the same effect as a downward moving positive current the integral under the current hump was 23 9 c when the velocity of the current pulse was between 0 25 c and 0 55 c the large sprite current was followed by impulsive electromagnetic radiation which has not been previously reported and could be a recoil effect similar to what is called a k change when it is observed in a lightning flash

analysis of the first gigantic jet recorded over continental north america 1 two low light cameras near marfa texas recorded a gigantic jet over northern mexico on 13 may 2005 at approximately 0423 50 utc assuming that the farthest of two candidate storm systems was its source the bright lower channel ended in a fork at around 50 59 km height with the very dim upper branches extended to 69 80 km altitude during the time window containing the jet extremely low frequency magnetic field recordings show that there was no fast charge moment change larger than 50 coulomb times kilometers c km but there was a larger and slower charge moment change of 520 c km over 70 ms the likely parent thunderstorm was a high precipitation supercell cluster containing a persistent mesocyclone with radar echo tops of at least 17 km however photogrammetric analysis suggests that the gigantic jet occurred over the forward flank downdraft region with echo tops of 14 km this part of the supercell may have had an inverted polarity charge configuration as evidenced by positive cloud to ground lightning flashes cg dominating over negative flashes cg while cgs occurred under the downwind anvil four minutes before the gigantic jet cg activity practically ceased in this area while cg rates increased culminating during the 20 s leading up to the gigantic jet with four national lightning detection network detected cgs a relative lull in lightning activity of both polarities was observed for up to 1 5 min after the gigantic jet the maturing storm subsequently produced 30 sprites between 0454 and 0820 utc some associated with extremely large impulse charge moment change values

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

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

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

contrasting nature of deformation along an intra arc shear zone the liquine ofqui fault zone southern chilean andes abstract the liquine ofquifault zone lofz cuts the patagonian batholith and the modern volcanic arc of southern chile for ca 1000 km the rock fabric along three transects of the lofz combined with new and published geochronological data suggest marked differences in the nature and timing of deformation along strike in the liquine transect 39 s a 1 km wide northeast striking subvertical mylonitic zone shows north plunging stretching lineations this mylonitic zone has been juxtaposed by high angle reverse faulting against a nearly undeformed miocene granitoid metamorphic assemblages and microstructures in the mylonites indicate greenschist facies conditions and sinistral reverse displacement deformation pre dates a 100 2 ma undeformed porphyritic dike hornblende 40ar 39ar mean age in the reloncavi transect 41 42 s deformation in cretaceous and miocene plutons is predominantly brittle kinematic analysis of two fault populations yields compressional and dextral strike slip stress regimes interpreted as late miocene in age in the hornopiren transect 42 43 s a 4 km wide mylonitic zone developed in plutons and wallrocks shows subhorizontal stretching lineations and dextral displacement a single fault population overprinting the mylonites supports a dextral strike slip stress regime available u pb k ar and 40ar 39ar dates on deformed cenozoic plutons and wallrock range from 9 to 13 ma on hornblende and from 6 to 3 ma on biotite microstructures and mineral assemblages indicate that the youngest ductile fabrics in the plutons formed at greenschist facies similar to the biotite ar closure temperature subparallel magmatic and solid state fabrics combined with geochronology suggest that dextral displacement was continuous during emplacement and cooling of the plutons dextral oblique subduction of the nazca plate beneath western south america has driven long term intra arc deformation at the southern andes plate boundary zone ridge collision in turn has favored dextral displacement at the leading edge of the continent since the pliocene

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

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

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

upward electrical discharges from thunderstorms blue jets gigantic jets cloud to cloud discharges and cloud to ground lightning are all electrical discharges from thunderclouds an analysis of numerical simulations and observations of these phenomena places them all in a unifying framework thunderstorms occasionally produce upward discharges called blue jets and gigantic jets that propagate out of the storm top towards or up to the ionosphere1 2 3 4 whereas the various types of intracloud and cloud to ground lightning are reasonably well understood the cause and nature of upward discharges remains a mystery here we present a combination of observational and modelling results that indicate two principal ways in which upward discharges can be produced the modelling indicates that blue jets occur as a result of electrical breakdown between the upper storm charge and the screening charge attracted to the cloud top they are predicted to occur 5 10 s or less after a cloud to ground or intracloud discharge produces a sudden charge imbalance in the storm an observation is presented of an upward discharge that supports this basic mechanism in contrast we find that gigantic jets begin as a normal intracloud discharge between dominant mid level charge and a screening depleted upper level charge that continues to propagate out of the top of the storm observational support for this mechanism comes from similarity with bolt from the blue discharges5 and from data on the polarity of gigantic jets6 we conclude that upward discharges are analogous to cloud to ground lightning our explanation provides a unifying view of how lightning escapes from a thundercloud

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

the zymoetz river rock avalanche june 2002 british columbia canada abstract on june 8 2002 the pacific northern gas pipeline in the zymoetz river valley was severed by a large debris flow the event initiated as a rock avalanche in glen falls creek a tributary of the zymoetz river the rock avalanche involved 1 106 m3 of volcaniclastic bedrock and travelled through a complex flow path to finally deposit a large fan in the main zymoetz river approximately half of the debris volume was deposited in the cirque basin at the head of the valley with the rest deposited in the channel and the fan examination of the initiation zone showed a very persistent slightly curved joint set that forms the main sliding surface for the failed block with a dip of 45 and dip direction of 300 a geographic information system gis was used to examine the event and allowed for further interpretation of field data preliminary dynamic analysis indicates that the event reached velocities of up to 34 m s comparison of the zymoetz river rock avalanche zrra with other similar events from the literature indicates that it exhibited similar mobility and velocities as evidenced from the literature these long runout events can cause significant damage and have the potential to be a very high risk as forestry and recreation activities spread further into remote areas

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

the liquine ofqui fault zone a long lived intra arc fault system in southern chile abstract plate reconstructions for the cenozoic document relatively steady right oblique subduction of the farallon nazca plate beneath the chilean continental margin the kinematic signature recorded along the intra arc liquine ofqui fault zone lofz a major feature of the southern andes may help to understand the way in which the nazca south america slip vector has been partitioned into strain and displacement along and across the continental margin the lofz consists of two nne trending right stepping straight lineaments a strike slip duplex at the right step and curved features which splay off the straight lineaments toward the northwest the lofz runs mostly through heterogeneously deformed cenozoic plutonic rock of the north patagonian batholith and patchy metamorphic wall rock early cenozoic volcano sedimentary rocks and dyke swarms found in close spatial association with the strike slip duplex are believed to have developed in strike slip related basins quaternary volcanoes are aligned parallel to the lofz both ductile and brittle kinematic indicators within centimeter to meter wide high strain zones document late cenozoic dextral shear deformation contrasting left lateral deformation recorded on older and wider mylonitic zones suggests that the lofz may be a long lived shear zone that accommodated continental scale deformation arising from the farallon nazca south america plate convergence a block rotation pattern as indicated by paleomagnetic data is consistent with the geometry and cenozoic kinematics of the lofz

observation of sprites over the asian continent and over oceans around taiwan 1 sprites were observed over thunderstorms in the southern china and in oceans around taiwan the observation sites were on the ali mountain of taiwan s central ridge area with an altitude of 2413 m and in the campus of national cheng kung university with an altitude of 50 m for the observed land sprites 90 of them were either carrots or columniforms and 64 of the sprites occurred in groups among the observed oceanic sprites 89 of them were carrots but only 22 of the sprites occurred in groups we define a sprite active system as a thunderstorm that continuously produces at least one sprite in a 10 minute interval the active sprites generating periods for the observed thunderstorms were typically shorter than 30 minutes the sprite production rates for these asian thunderstorms are estimated to be between i 2 10 4 events km2 hr and i 1 10 3 events km2 hr

a thermodynamic kinematic and microphysical analysis of a jet and gigantic jet producing florida thunderstorm this paper presents a meteorological analysis of a storm that produced two jets four gigantic jets gj and a starter which were observed by two radars as well as the kennedy space center 4 dimensional lightning surveillance system on 3 august 2013 in central florida the work is the first application of dual polarization data to a jet producing storm and is the fifth case related to a tropical disturbance the storm environment is consistent with the moist tropical paradigm that characterizes about three quarters of the surface and aircraft observed jet and gj events the most unstable mu convective available potential energy is not unusual for florida summer convection and is below the climatological mean for these events an unusual speed shear layer is located near the storm equilibrium level el and the storm exhibits a tilted structure with cgs displaced upshear the turbulence as measured by the eddy dissipation rate is extreme near the storm top during the event window consistent with the gj mixing hypothesis the individual events are collocated with and track along the center axis of the divergent outflow at the el and occur within the region of the coldest goes ir temperatures placing the events within the overshoot the dual polarization data indicate a deep graupel column extending above the mixed phase layer to a 13 km altitude

blue starters brief upward discharges from an intense arkansas thunderstorm this paper documents the first observations of a new stratospheric electrical phenomenon associated with thunderstorms on the night of 30 june ut 1 july 1994 30 examples of these events which we have called blue starters were observed in a 6 m 44 s interval above the very energetic arkansas thunderstorm where blue jets were first observed the blue starters are distinguished from blue jets by a much lower terminal altitude they are bright and blue in color and protrude upward from the cloud top 17 18 km to a maximum 25 5 km 83 655 ft in altitude all blue starters events were recorded from two small areas near texarkana texas arkansas where hail 7 0 cm in diameter was falling comparison to cloud to ground cg lightning flashes revealed 1 blue starters were not observed to be coincident with either positive or negative cg flashes but they do occur in the same general area as negative cg flashes 2 cumulative distributions of the negative cg flashes in 5 s before and after the starter and within a radius of 50 km shows a significant reduction for about 3 s following the event in the two cells where starters and jets were observed the energy deficit is approximately 109 j it is possible that blue starters are a short lived streamer phenomenon

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

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

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

characteristics of infrasound from lightning and sprites near thunderstorm areas 1 research about thunder was mainly performed 20 30 years ago but has been renewed in recent years due to new interest about infrasound in the framework of the verification of the compliance of the comprehensive nuclear test ban treaty during the eurosprite 2005 campaign an infrasound miniarray has been set up in france to measure the characteristics of infrasound from lightning and sprites when these kinds of sources were close to the sensors that is for lightning distances lower than 100 km and sprite distances lower than 300 km for two large thunderstorms which passed over the station detection conditions of infrasound from lightning are detailed and some characteristics are thoroughly described e g amplitude variation with distance and spectrum of an individual event in the frequency range from 0 01 to 10 hz the locations of infrasound sources are determined using a 3 d inversion infrasound signals from sprites have also been detected and the 3 d inversion method used for lightning infrasound has been adapted to locate the sources of infrasound from sprites four different sprite infrasound events are analyzed in this way the infrasound source corresponds well to the sprite spatial characteristics deduced from camera observations questions about generation mechanisms of infrasound from lightning and sprites still remain these new results should help us to understand the sound generation processes

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

deformed symmetrical volcanoes analog modeling of volcanic cones traversed by strike slip faulting was conducted and the cones were analyzed for deformation characteristics the study shows that symmetrical volcanoes that have undergone basal strike slip offset may be deformed internally without manifesting any change in their conical shape volcanoes deformed by strike slip faulting may already have well developed fractures in their interior yet still appear as a symmetrical cone exhibiting concentric contours when viewed on a topographic map moreover slight changes in the basal shape of the cone induced by strike slip movement can be restored by the relatively faster resurfacing and reshaping processes from the deposition of younger eruptive products these findings pose a subtle but significant point in the assessment of volcanic landslide hazards not all perfect cones are undisturbed the detection of concealed deformation is important because fractures induce further instability in volcanoes and act as slip planes during volcano collapse events there are many examples of symmetrical volcanoes in nature the faultless appearance of such perfect cones can be misleading which requires careful attention in hazards assessment

lightning development associated with two negative gigantic jets 1 we report observations of two negative polarity gigantic jets sufficiently near very high frequency vhf lightning mapping networks that the associated lightning characteristics and charge transfer could be investigated in both cases the gigantic jet producing flash began as ordinary intracloud lightning with upper level channels attempting to exit the cloud and then produced the upward gigantic jet neither flash had developed channels to ground confirming that the major charge transfer during gigantic jets occurred between the cloud and ionosphere the leader progression of one event was detected at altitudes above 20 km demonstrating the possibility of detecting and tracking the propagation of negative jets above the cloud with vhf techniques citation lu g et al 2011 lightning development associated with two negative gigantic jets geophys res lett 38 l12801

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

photographic and lightning mapping observations of a blue starter over a new mexico thunderstorm 1 on 4 august 2010 a small blue starter was observed over an active thunderstorm in west central new mexico the storm was of normal polarity with upper positive charge over midlevel negative charge the event was visually observed and photographed and mapped by the lightning mapping array lma at langmuir laboratory the blue starter occurred during a seven stroke negative cloud to ground cg flash that was detected by the national lightning detection network nldn and data from the lma show that it initiated between upper positive charge and inferred negative screening charge at the cloud top upward positive streamers of the blue starter emerged from the cloud top at 15 2 km altitude and reached a terminal altitude of 17 km the observation confirms that blue starters can be initiated by the electric field changes associated with cg flashes which enhance the electric field between upper positive charge and negative screening charge it also confirms that the upward leaders and streamers of blue starters in normal polarity storms are of positive polarity

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

multi instrumental observations of a positive gigantic jet produced by a winter thunderstorm in europe 1 at 2336 56 utc on 12 december 2009 a bright gigantic jet gj was recorded by an observer in italy forty nine additional sprites elves halos and two cases of upward lightning were observed that night the location of the gj corresponded to a distinct cloud top 34 c west of ajaccio corsica the gj reached approximately 91 km altitude with a trailing jet reaching 49 59 km matching with earlier reported gjs the duration was short at 120 160 ms this is the first documented gj which emerged from a maritime winter thunderstorm only 6 5 km tall showing high cloud tops are not required for initiation of gjs in the presence of strong vertical wind shear the meteorological situation was different from typical outbreaks of fall and winter thunderstorms in the mediterranean during the trailing jet phase of the gj a sprite with halo triggered by a nearby cloud to ground lightning flash occurred at a relatively low altitude 72 km at the same time the trailing jet and beads were reilluminated electromagnetic waveforms from hungary poland and the usa revealed this gj is the first reported to transfer negative charge approximately 136 c from the ionosphere to the positively charged origins in the cloud i e a positive cloud to ionosphere discharge ci with a large total charge moment change of 11600 c km and a maximum current of 3 3 ka early vlf transmitter amplitude perturbations detected concurrently with the gj confirm the production of large conductivity changes due to electron density enhancements in the d region of the ionosphere

subionospheric early vlf perturbations observed at suva vlf detection of red sprites in the day 1 first observations of early very low frequency vlf perturbations on signals from nwc 19 8 khz and npm 21 4 khz monitored at suva in the month of november 2006 are presented the early fast early slow early short rord and step like early vlf perturbations are observed on signals from both the transmitters the early fast vlf events are found to occur more often in the nighttime than in the daytime whereas step like early events predominantly occur in the daytime most of the early vlf events are associated with amplitude changes between 0 2 0 8 db with only a few cases 0 8 db in general the recovery time of daytime early fast vlf events is less when compared to the nighttime early fast vlf events the lightning location data provided by the world wide lightning location network and broadband vlf data recorded at suva have been analyzed to identify the location of causative lighting discharges along the great circle paths between transmitter and receiver and the sferics associated with causative lightning of early vlf events this research is the first to report both daytime early fast vlf perturbations with faster recovery and also step like early vlf perturbations initiated and ended by the lightnings which are most likely associated with red sprites and or elves occurring in the daytime

gigantic jets produced by an isolated tropical thunderstorm near reunion island five gigantic jets gjs have been recorded with video and photograph cameras on 7 march 2010 above an isolated tropical storm east of reunion island three of them were produced before the storm reached its coldest cloud top temperature approximately 81 c and two others occurred during the cloud extension thanks to the close distance of observation 50 km the luminosity within the cloud was recorded and the events are analyzed in unprecedented detail the tops of the gjs are estimated between 80 and 90 km all these gjs are accompanied by long continuous cloud illumination and they are preceded and followed by intermittent optical flashes from the cloud most of time without any cloud to ground cg flash simultaneously detected which suggests they originated mainly as intracloud discharges and without any charge transfer to earth the cg lightning activity is observed to cease a few tens of seconds before the jets according to elf data recorded at nagycenk hungary the five gjs serve to raise negative charge their duration ranges from 333 to 850 ms the leading jet has the most variable duration 33 167 ms and propagates faster at higher altitudes the trailing jet exhibits a continuous decrease of luminosity in different parts of the jet lower channel transition zone and for most events carrot sprite like top and in the cloud with possible rebrightening the lower channels 20 40 km altitude produce blue luminosity which decreases with altitude and become more and more diffuse with time the transition zone around 40 65 km consists of bright red luminous beads slowly going up 104 m s 1 retracing the initial leading jet channels

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

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

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

time resolved sprite imagery fleeting columns of luminosity occurring above large thunderstorms at 50 90 km altitude presently known as sprites were imaged with an intensified video charge coupled device ccd camera during a july 1995 ground based campaign near fort collins colorado these unfiltered intensified images reveal detailed spatial structure within the sprite envelope the temporal resolution of standard interlaced video imagery is limited by the 60 fields per second acquisition rate 16 ms the specific ccd used here however is subject to bright events leaking into the readout registers allowing time resolution on the order of the linescan rate 63 s typical sprite onset is found to follow the associated cloud lightning by 1 5 to 4 ms the onsets of the individual sprites within a cluster are generally but not always simultaneous to within 1 ms sprites tend to have a bright localized core less than 2 km in horizontal dimension which rises to peak intensity within 0 3 ms and maintains this level for 5 to 10 ms before fading over an additional 10 ms

high speed intensified video recordings of sprites and elves over the western mediterranean sea during winter thunderstorms we report the first intensified high speed video images of elves sprites and halos observed in europe all the events corresponded to winter season thunderstorms over the mediterranean sea the observations comprise many elves generated by both cloud to ground lightning current polarities in 8 of the 14 sprite observations we observed an elve previous to the sprite in three cases we observed also an elve quickly followed by a halo and a sprite in several observations we observed lightning light before the mesospheric transient luminous event we present a case where the lightning from cloud tops was visible during the entire event thanks to the high speed videos and their resolution and low intensifier phosphor persistence we analyzed the timing distribution of the development phase of sprite elements the persisting luminosity phase and the total duration finally we summarize one particular observation where a streamer collides and bounces with a previous formed column it may be a new phenomenon of collision between an existing column body that interacts with a later streamer point like tip which is not merged and attached

landslide and tsunami hazard at yate volcano chile as an example of edifice destruction on strike slip fault zones the edifice of yate volcano a dissected stratocone in the andean southern volcanic zone has experienced multiple summit collapses throughout postglacial time restricted to sectors ne and sw of the summit the largest such historic event occurred on 19th february 1965 when 6 1 10 106 m3 of rock and ice detached from 2 000 m elevation to the sw of the summit and transformed into a debris flow in the upper part of the flow path velocities are estimated to have reached 40 m s 1 after travelling 7 500 m and descending 1 490 m the flow entered an intermontane lake lago cabrera a wavemaker of estimated volume 9 3 106 m3 generated a tsunami with an estimated amplitude of 25 m and a run up of 60 m at the west end of the lake where a settlement disappeared with the loss of 27 lives the landslide followed 15 days of unusually heavy summer rain which may have caused failure by increasing pore water pressure in rock mechanically weathered through glacial action the preferential collapse directions at yate result from the volcano s construction on the dextral strike slip liquine ofqui fault zone movement on the fault during the lifetime of the volcano is thought to have generated internal instabilities in the observed failure orientations at 10 to the fault zone in the riedel shear direction this mechanically weakened rock may have led to preferentially orientated glacial valleys generating a feedback mechanism with collapse followed by rapid glacial erosion accelerating the rate of incision into the edifice through repeated landslides debris flows with magnitudes similar to the 1965 event are likely to recur at yate with repeat times of the order of 102 years with a warming climate increased glacial meltwater due to snowline retreat and increasing rain at the expense of snow may accelerate rates of edifice collapse with implications for landslide hazard and risk at glaciated volcanoes in particular those in strike slip tectonic settings where orientated structural instabilities may exist