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

complete dynamic modeling calibration for the thurwieser rock avalanche italian central alps abstract few rock avalanches have been witnessed and no exact real time description is available the 2 5 m m 3 punta thurwieser rock avalanche september 2004 italian central alps is a unique event for which many quantitative observations have been gathered this is the first case ever of a natural rock avalanche being recorded on video and for which an almost exact value of the total time duration from initial detachment to final deposition is available the landslide travelled over 2 9 km from its source partially in a glacial environment the initial failure and the time for the complete evacuation of the source area were studied and assessed by a series of photos the mean front velocities along the path have been estimated from the video the final geometry and the characteristics of the deposit have been obtained by gps measurements aerial photos field surveys and laboratory tests a quasi 3d continuum dynamic analysis of the landslide motion has been performed assuming both a voellmy and a frictional rheology in the model dan 3d for the first time the landslide front velocities have been used for back analyses and calibration of the rheological parameters together with the final shape and thickness of the deposit and its developing extension the dynamic flow resistance parameters initially calibrated with dan were adopted and validated in dan 3d showing good consistency they are consistent with the existing database for calibrated landslides of similar type and scale flow velocities on the path segment underlain by glacial deposits up to 55 65 m s 1 are more accurately predicted by adopting a frictional rheology up to 50 55 m s 1 with zero pore pressure and a 26 friction angle than by a voellmy rheology up to 40 45 m s 1 both observations and modelling show that glacial ice plays a substantial role in increasing the rock avalanche mobility

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

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

estimating glacier bed overdeepenings as possible sites of future lakes in the de glaciating mont blanc massif western european alps de glaciating high mountain areas result in new landscapes of bedrock and debris where permafrost can degrade persist or even newly form in cases and of new lakes in glacier bed overdeepenings gbos becoming ice free these landscapes with new lakes in close neighborhood to over steepened and perennially frozen slopes are prone to chain reaction processes e g rock ice avalanches into lakes triggering impact waves dam breach or overtopping and debris flows with potentially far reaching run out distances causing valley floors devastation the frequency magnitude and zonation of hazards are shifting requiring integrative approaches combining comprehensive information about landscape evolution and related processes to support stakeholders in their adaptation strategies in this study we intend to setup an essential baseline for such an integrative approach in the mont blanc massif mbm which is a typical high mountain range affected by de glaciation processes we first i predict and ii detect potential gbos by combining the glabtop model with a visual analysis based on morphological indications of glacier flow through over deepened bed parts we then iii determine the level of confidence concerning the resulting information and iv estimate the approximate time range under which potential lakes could form the location of the predicted gbos and the shape of glacier beds are evaluated against currently forming water bodies at retreating glacier snouts and seismic and ice penetrating radar measurements on the argentiere glacier this comparison shows that the location of predicted gbos is quite robust whereas their morphometric characteristics depth volume are highly uncertain and tend to be underestimated in total 48 80 of the predicted or detected gbos have a high level of confidence in addition to five recently formed water bodies at glacier snouts one of the high confidence gbos talefre glacier which is also the most voluminous one could form imminently during coming years if not partially or totally drained through deeply incised gorges at the rock threshold twelve other lakes could form within the first half of the century under a constant or accelerated scenario of continued glacier retreat some of them are located below high and permanently frozen rock walls prone to destabilization and high energy mass movements hinting at possible hot spots in terms of hazards in the coming decades where more detailed analysis would be required

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

friction and dynamics of rock avalanches travelling on glaciers rock avalanches travelling on glaciers often exhibit effective friction coefficient lower than those on a rocky terrain after briefly considering some data of rock avalanches on glaciers the physics of sliding of solid objects on icy surfaces is reviewed and a model is put forward for the mechanics of rock avalanche sliding on ice accounting for the formation of a natural lubricating layer it is suggested that at the beginning of the flow of a rock avalanche friction results from rocky blocks ploughing on ice as the erosion continues a gouge of ice particles results which clogs the interstices between blocks and may partially melt as a consequence of the production of frictional heat this conceptual model is numerically investigated for a slab travelling on ice the results show an increase in mobility as a function of slab thickness travelled length and the gravity field in agreement with case studies the results are useful to interpret the peculiar features of rock avalanches travelling on icy surfaces such as digitations out runner blocks and longitudinal furrows the lubrication theory for landslides on ice proposed here may provide a framework for understanding landslides on earth and for future modelling in addition it may help elucidate the presence of similar landslide deposits on the surface of mars

testing landslide and atmospheric effects models for the formation of double layered ejecta craters on mars double layered ejecta dle craters are distinctive among the variety of crater morphologies observed on mars but the mechanism by which they form remains under debate we assess two ejecta emplacement mechanisms 1 atmospheric effects from ejecta curtain induced vortices or a base surge and 2 ballistic emplacement followed by a landslide of ejecta assisted by either surface or pore ice we conduct a morphological analysis of the ejecta facies for three dle craters which impacted into irregular pre existing topography we find that the unique topographic environments affected the formation of grooves and the inner facies and thus appear to be inconsistent with an atmospheric effects origin but are supportive of the landslide hypothesis we distinguish between the two landslide models lubrication by either surface or pore ice by assessing relationships between dle crater ejecta and morphologic features indicative of buried ice deposits including sublimation pits ring mold craters expanded secondary craters and excess ejecta craters the association of dle craters with these features suggests that surface ice was present at the time of the impacts that formed the dle craters we also compare the froude numbers of dle crater ejecta to landslides and find that the ejecta of dle craters are kinematically and frictionally similar to terrestrial landslides that overran glaciers this suggests that the grooves on dle craters may plausibly form through the same shear splitting mechanism as the landslides in summary our analysis supports the hypothesis that dle craters form through meteoroid impacts into decameters thick surface ice deposits emplaced during periods of higher obliquity followed by ejecta sliding on the ice

longitudinal ridges in mass movement deposits prominent longitudinal features are often reported on the surfaces of mass movement deposits however the genesis and implications of these have not hitherto been considered and herein we present preliminary observations of their occurrence both in the field and in the laboratory elongated ridges are often oriented sub parallel to the flow direction and aligned radially from the source due to debris spreading they are particularly prominent in large 106m3 rock avalanches emplaced onto deformable substrates and are also found in the proximal reaches of volcanic debris avalanches flowbands which are longer and thinner expressions of longitudinal ridges are continuous along the entire flow length and are observed in rock avalanches emplaced onto glaciers in snow and some ice avalanches in pyroclastic flows and some block and ash flows in ejecta sheets in extraterrestrial landslides and in some volcanic debris avalanches other volcanic debris avalanches and the distal areas of rock avalanches often display hummocks that are aligned radially from the source we propose that these aligned hummocks are remnants of longitudinal ridges the formation of elongate ridges and their expressions as flowbands aligned hummocks or distal lobes and digits in qualitatively similar fashion in both laboratory and field environments suggests they represent an intrinsic tendency of granular flows in a wide range of situations

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

characteristics and transport mechanism of the nyixoi chongco rock avalanche on the tibetan plateau china abstract for studying rock avalanches complex surficial and internal characteristics have been regarded as important indicators for understanding avalanche transport mechanism in the present study deposits of a massive holocene rock avalanche termed the nyixoi chongco rock avalanche located on the lhasa terrane of tibetan plateau in china are investigated based on a combination of remote sensing data and in situ observations it is revealed that abundant surface landforms including toreva blocks longitudinal and transverse ridges en echelon ridges and hummocks are commonly developed corresponding to these surface morphologies a series of internal sedimentary structures including jigsaw structures inner shear zones aligned clasts diapiric structures convoluted laminations and basal decollements are also well developed through an analysis of these surficial and internal characteristics we propose that a rapid motion similar to a laminar flow most likely occurred after the avalanche mass detaching from the source area in this process the detached avalanche mass was mainly emplaced by a frictional simple shear process characterized by a bulldozing effect that occurred between the sliding mass and the substrate from the proximal to the distal sections of the avalanche the transport of the rock mass can be classified into four major processes an extension dominated sliding process in the transition zone a compression dominated sliding process in subzones iii 1 and iii 2 of the accumulation zone iii a sliding process co dominated by compression and lateral spreading in subzone iii 3 and a rapid radial spreading process in subzone iii 4 the results of our study provided an improved understanding of the transport mechanisms of this rock avalanche

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

global scale analysis of martian landslide mobility and paleoenvironmental clues the mobility of landslides on mars is studied based on a database of 3 118 events to establish the volume of the landslides for the whole dataset based on the deposit area a new volume area relationship based on a representative dataset of 222 landslides is used plotting the h l ratio between fall height h and runout l versus volume landslide mobility is analyzed and compared with existing empirical relationships for martian and terrestrial landslides analyzing the mobility in terms of normalized residuals i e the relative deviation of the h l ratio from the dataset best fit line mobility is found to depend on both the landslide location on mars and landslide typology this allows us to identify four different types of high mobility hypermobile landslides three classes of high mobility landslides are associated respectively to meteoroid impact the olympus mons aureoles and landslides with toreva block failure style and their mobility can be explained by the peculiar flow mechanics the fourth class includes landslides associated with isolated craters those in the regions wetted by the putative oceanus borealis and the ones at high latitudes we suggest that the common factor behind all the hypermobile landslides of this fourth kind is the presence of ice this is confirmed by our data showing that landslides increase in mobility with latitude the latitudinal trend mirrors the distribution of ice as detected by radar neutron probes and the presence of glacial and layered ejecta morphologies because the overall landslide distribution supports the presence of ice lubricated conditions two ice lubrication models are presented showing how ice melting within or underneath the landslides could enhance mobility by proper analysis in terms of apparent friction residuals we find that the mobility of landslides in valles marineris with the largest landslide concentration is lower than average we explain this circumstance partly from the smaller role of ice in equatorial valles marineris and partly because the collapses from high slope relief imply high speed impact with the floor valley confinement loss of momentum and decrease in mobility environmental consequences imply that the present subsurface ice distribution may have been persistent throughout the amazonian period

diagnostic characteristics and paleodynamics of supraglacial rock avalanches innerdalen western norway abstract misinterpretation of rock avalanche deposits in mountain environments is not uncommon because of the complex interactions between rock avalanches and glaciers this paper for the first time presents a detailed description of suspicious rock boulder deposits which are remnants of a rock avalanche onto a late pleistocene glacier the boulder deposits cover around 1 1 km 2 and are distributed over an area of around 7 5 km 2 and a variety of landforms three closely nested distinct terminal moraines 0 45 km 2 and dislocated terminal moraines 0 34 km 2 entirely built up of large boulders lateral moraines that decrease in elevation over a short distance and connect to the terminal moraines small patches 0 02 km 2 of boulders that occur in islands on a peat dominated valley floor and large patches of boulder fields 0 25 km 2 in size hanging 350 m above the valley floor the latter are disconnected from any potential source area 10 be cosmogenic nuclide ages of the three terminal moraines give an indistinguishable late pleistocene age of 13 6 1 4 ka whereas the largest boulder field that is located on the opposite side of the valley from the failed mountain yields a 10 be age of 14 1 0 4 ka which is slightly older but indistinguishable from the moraine deposits within uncertainty margins all boulder deposits add up to a volume of 31 10 6 m 3 the interpretation of a single rock avalanche source for those landforms is further confirmed by numerical runout modeling using dan3d a failure of the entire volume from skarfjellet mountain would result in a runout pattern that is identical to that of the distributed boulder fields when considering that the valley was filled with a glacier around 350 m thick the rock avalanche would not reach the position of the terminal moraines however a glacial re advance could have transported the boulders to that position the late pleistocene rock avalanche was followed by a holocene rock avalanche with a volume of 23 10 6 m 3 and a typical lobate deposit damming the innerdalen valley and creating a lake 10 be ages indicate that this event occurred 7 97 0 94 ka ago structural measurements performed on high resolution lidar scans show a strongly jointed source rock with three joint sets with dip dip direction 81 034 86 331 and 77 354 and a foliation with 22 003 the kinematic of the failures can thus be a combination of small scale wedge failures and planar sliding on shallow dipping foliation our detailed description can enable a better identification and interpretation of similar deposits in other mountain areas

the pandemonium creek rock avalanche british columbia in 1959 a rock spur became detached from the headwall of a cirque near pandemonium creek in the southern coast mountains of british columbia approximately 5 000 000 cu m of blocky gneissic quartz diorite debris travelled 9 0 km along a highly irregular path descending a vertical distance of 2 km to the valley of south atnarko river the high mobility of the rock avalanche is manifested by superelevation in valley bends two run ups and two right angle changes in flow direction this mobility is due in part to 1 peculiarities in the path of the landslide lateral moraines for example funnelled and accelerated the debris and 2 travel over a glacier below the detachment zone although most of the debris came to rest on the upper part of a fan at the mouth of pandemonium creek one lobe traversed the fan and entered knot lakes where it generated displacement waves that destroyed trees along the shore run up and superelevation data indicate that the debris was moving between 81 and 100 m s as it entered the run up zone at pandemonium creek and 21 38 m s in pandemonium valley to the east these velocities were analysed by applying the dynamic model of h j korner rock mechanics 1976 8 225 256 to the path of the landslide the analysis suggests that the rock avalanche had two phases a very rapid initial phase from detachment to the beginning of the run up and following sudden energy losses at the run up a second phase involving much lower velocities the pandemonium creek landslide is similar in many respects to much larger highly mobile rock avalanches in other parts of the world for example huascaran peru and little tahoma peak washington u s a although much less common than rockfalls and debris flows rock avalanches are capable of far greater damage this is a consequence of their size and the fact that they travel great distances at high velocities the potential exists for other highly mobile landslides of the pandeminium creek type in the mountains of western canada highlighting the need for caution in the future development of this region

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

rock avalanches that travel onto glaciers and related developments karakoram himalaya inner asia abstract catastrophic rock slope failures in rugged terrain commonly generate rock avalanches when these occur in glacier basins the extent of landslide run out and its emplacement geometry are affected by movement over ice substantial modifications of glacier activity and sedimentation can follow ice activity leads to rapid modification transport and dispersal of landslide debris the nature of these interactions is described from observations over 20 years at bualtar glacier in the karakoram in august 1986 rock avalanches descended onto the ablation zone of the glacier their moisture content and patterns of deposition were affected by travel over ice glacier movement increased sharply at and below the rock avalanche deposits and within a few months the glacier surged a second surge occurred 2 years later major slope failures and debris flows were triggered beyond the ice margins and ponded melt water led to small outburst floods by 2005 the landslide material had been transported some 9 km about one third of this distance in the surges eventually it was fully reworked to become less readily distinguishable from other heavy supraglacial debris a large area of thickened ice persisted where the debris reduced ablation a positive impact on mass balance equivalent to a 20 increase in annual accumulation however it occurred as a moving segment of the ablation zone in 10 years it had in effect replaced the mass transferred in the surges data for the mid 1980s indicate the rock avalanches exceeded pre existing supraglacial debris by roughly five times and over a 30 year period will equal almost 500 years of normal supraglacial transport to the glacier margins other impacts of the episode suggest a doubling of this contribution to denudation similar developments were observed at three other glaciers where recent rock avalanches occurred and at twenty one prehistoric rock avalanches newly identified as having spread over glaciers it seems inadequate to treat such events only as singular extremes or the landslide and glacial processes separately here they are interpreted as contributing to disturbance regime landscapes whose history reflects episodic and regionally specific responses to strong interference among different earth surface processes they generate polygenetic deposits and landforms that are morphologically complex individual episodes involve decades to millennia their numbers and repetition can over ride or redirect geotectonic and climatic conditions it is suggested they are major but hitherto misread or neglected elements of landform evolution in the karakoram and perhaps in other high mountains

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

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

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

the tsiolkovskiy crater landslide the moon an lroc view abstract evidence suggests that the lobate flow feature that extends 72 km outward from the western rim of tsiolkovskiy crater is a long runout landslide this landslide exhibits three possibly four morphologically different parts likely caused by local conditions all of these plus the ejecta of tsiolkovskiy crater and its mare fill are approximately of the same crater model age i e 3 55 0 1 ga the enormous size of this landslide is unique on the moon and is a result of a combination of several geometric factors e g its location relative to fermi crater and that tsiolkovskiy crater was an oblique impact that produced an ejecta forbidden zone on its western side schultz 1976 the landslide formed in this ejecta free zone as the rim of tsiolkovskiy collapsed and its debris flowed across the relatively smooth flat floor of fermi crater in this location it could be easily identified as a landslide and not ejecta its mobility and coefficient of friction are similar to landslides in valles marineris on mars but less than wet or even dry terrestrial natural flows this suggests that the mars landslides may have been emplaced dry the high density of small craters on the landslide is likely an illusion caused by the effects of age related differences in regolith thickness on crater morphology and the presence of the abundant young circular secondary craters produce by debris ejected from distant fresh craters

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

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

rheological constraints on martian landslides we use a dynamic finite difference model to simulate martian landslides in the valles marineris canyon system and olympus mons aureole using three different modal rheologies frictional bingham and power law the frictional and bingham modes are applied individually fluidized rheology is treated as a combination of frictional and power law modes general fluidization can include pore pressure contributions whereas acoustic fluidization does not we find that general fluidization most often produces slides that best match landslide geometry in the valles marineris this implies that some amount of supporting liquid or gas was present in the material during failure the profile of the olympus mons aureole is not well matched by any landslide model suggesting an alternative genesis in contrast acoustic fluidization produces the best match for a lunar slide a result anticipated for dry crust with no overlying atmosphere the presence of pressurized fluid during valles marineris landsliding may be due to liquid water beneath a thin cryosphere 1 2 km or flash sublimation of co2

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

subaqueous rock avalanche deposits exposed by post glacial isostatic rebound innfjorddalen western norway abstract this paper presents a detailed description of deposits and landforms of multiple rock avalanches in western norway one of which fell onto water saturated sediments in innfjorddalen below the former water level deposits of the latter are now exposed on the valley floor due to post glacial isostatic rebound at least three rock avalanches from the same source at grafonnfjellet mountain have occurred during late glacial and post glacial time and their deposits are distributed over an area of 1 44 km 2 in the valley these rock avalanches have volumes of 15 1 10 6 m 3 5 4 10 6 m 3 and 0 3 10 6 m 3 and yielded cosmogenic radionuclide 10 be ages of 14 3 1 4 ka 8 79 0 94 ka and 1 028 0 380 ka respectively the youngest event dates within uncertainty limits to a historic rock avalanche in the year 1611 12 ce the rock avalanches formed a stratified succession of deposits the rock avalanche deposits 1 38 m 2 have lobate forms have frontal rims and parallel ridges extend across the valley floor and up the opposite slope and form dams on the valley floor isolated hills comprised of rock boulders 0 61 km 2 interpreted to be toma hills are disconnected from the main rock avalanche deposits by a 520 m wide zone of deformed valley fill sediments trenches and a ground penetrating radar survey of these deposits indicate large scale deformation or liquefaction numerical runout modeling of the rock avalanches with the code dan3d supports the interpretation of their landforms and sources and highlights their runout behavior

apparent tidal influence on magmatic activity at oldoinyo lengai volcano tanzania as observed in moderate resolution imaging spectroradiometer modis data this paper investigates the relative timing of solid earth tides and thermal anomalies associated with volcanic activity at oldoinyo lengai ol tanzania from 2000 to 2008 the low viscosity of ol s carbonatite magmas may make it particularly susceptible to tidal stresses thermal data from the moderate resolution imaging spectroradiometer modis were filtered using the modlen algorithm and earth tides were modeled using tsoft application of the schuster and chi squared tests resulted in apparent correlations between times of thermal anomalies and the phase of the semi diurnal and biannual solid earth tides however for semi diurnal and biannual tides limited acquisition times of the modis data account for the apparent correlations re examining the data while accounting for the bias introduced by the limited acquisition times correlations are no longer found onset times of eruptive events and times of thermal anomalies show no statistically significant correlation with the fortnightly tide indicating this is not an influence on activity at ol tidal influences on magmatic activity if at all present cannot be observed in coarse resolution thermal data on semi diurnal and fortnightly time scales based on the available data correlations on biannual timescales cannot be ruled out

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

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

modelling rock avalanche propagation onto glaciers abstract ice rock avalanches which occur in glacial environments are controlled by the presence of snow and ice in the moving material and by possible propagation onto icy basal surfaces all these factors contribute to enhancing the flow mobility mixing with ice and snow hampers block collisions and favours dense flow behaviour ice melting reduces granular friction by saturation of the basal material and fluidization effects propagating onto glaciers offers a smooth surface with low shear resistance this work is a review of the best documented ice rock avalanches and focuses on evaluating their mobility for hazard analysis purposes by providing a set of calibrated cases the rock avalanches have volumes ranging from 5 10 6 m 3 to 25 10 6 m 3 we replicate these events by using sph and fem numerical methods assuming frictional and voellmy basal rheologies the voellmy rheology best performs at replicating the landslide propagation among the back analyzed cases the frictional coefficient ranges in the interval 0 03 0 1 the turbulent coefficient within 1000 m s 2 2000 m s 2 the bulk basal friction angle ranges within 2 75 and 14 with values inversely related to event volumes forward selection of the basal friction angle based on event volume allows the replication of the mount cook ice rock avalanche predicting a maximum runout which is less than 4 larger than observed in the perspective of forward modelling large uncertainty is related to the reconstruction of the post event topographies particularly for the sliding surface mixing with ice and snow reduces basal friction proportionally to ice and snow content pure ice has a basal friction which is reduced by about 75 than basal friction of pure rock melting of ice during rock avalanche propagation has been evaluated for the sherman event the frictional heat generated at the glacier surface results in the melting of 86 2 5 9 kg m 2 which could have contributed to a minimum 20 35 10 reduction of the material friction angle through the sole pore pressure generation within a 40 and 20 cm thick shear layer respectively the largest uncertainty is related to the area of contact between rock and ice

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

an overview of recent large catastrophic landslides in northern british columbia canada at least thirty eight large catastrophic landslides each either larger than 0 5 m m 3 or longer than 1 km have occurred in northern british columbia in the last three decades the landslides include low gradient flowslides in cohesive sediments long runout rock slides rock avalanches and complex rock slide flows the flowslides have occurred in a variety of sediments including glaciolacustrine silt clay rich till and clay rich colluvium the rock failures have happened in weak shale overlain by sandstone and volcanic rocks the frequency of large landslides in northern british columbia appears to be increasing suggesting a link to climate change d 2005 elsevier b v all rights reserved

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

one million cubic kilometers of fossil ice in valles marineris relicts of a 3 5 gy old glacial landsystem along the martian equator abstract self consistent landform assemblages suggest that valles marineris the giant valley system that stretches along the martian equator was entirely glaciated during late noachian to early hesperian times and still contains huge volumes of fossil ice some of these glacial landform assemblages are illustrated here with representative examples selected in three regions ius chasma central candor chasma and the junction between coprates chasma and capri chasma a morphological boundary separating an upper spur and gully morphology from a smooth basal escarpment has been spectacularly preserved along valley walls throughout valles marineris the boundary winds around topographic obstacles and displays long wavelength variations in elevation it is associated with lateral benches hanging valleys and truncated spurs comparisons with terrestrial analogs indicate that it is most reasonably interpreted as a glacial trimline chasma floors are covered by various kinds of terrains including hummocky terrains platy terrains lateral banks layered benches and a draping mantle landforms in these terrains and their spatial relationship with the interpreted trimline suggest that they correspond to various disintegration stages of an ancient glacial fill currently protected by a superficial cover of ablation till altogether these landforms and terrains compose a full glacial landsystem with wet based glaciers that were able to flow and slide over their beds it was most probably fed by ice accumulating at low elevations directly from the atmosphere onto valley floors and walls with only minor contributions from tributary glaciers flowing down from higher elevations similar fossil glacial landsystems dating back from the early martian history are to be expected in many other low latitude troughs such as chasmata chaos valleys impact craters and other basins

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

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

fragmentation in the val pola rock avalanche italian alps 1 grain size data from the deposit of the 1987 val pola rock avalanche central italian alps are compared with data concerning rock avalanching rock fragmentation and comminution the weibull distribution fits a small part of the entire particle size distribution of debris samples with a mean value of the curve shape factor of 0 54 0 28 this is typical of multiple comminution or fragmentation with much shearing a fractal distribution fits over a greater size range computed fractal dimensions range between 1 3 and 3 2 within the deposit with average values of about 2 6 2 7 these values cover the range between the theoretical values of the plane of weakness model 1 97 and the pillar of strength model 2 84 and are close to the theoretical value for the constrained comminution model 2 58 these suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process a variety of different physical and empirical laws suggest that 1 30 of the energy expended in the rock avalanche was consumed in fragmentation

catastrophic detachment and high velocity long runout flow of kolka glacier caucasus mountains russia in 2002 abstract in september 2002 a catastrophic geomorphic event occurred in the caucasus mountains southern russia in which almost the entire mass of kolka glacier detached from its bed accelerated to a very high velocity max 65 80 m s and traveled a total distance of 19 km downstream as a glacier debris flow based on the interpretation of satellite imagery obtained only 8 5 h before the event occurred the analysis of seismograms from nearby seismic stations and subsequent detailed field observations and measurements we suggest that this remarkable event was not a response to impulse loading from a rock avalanche in the mountainside above the glacier or to glacier surging but due entirely to the static and delayed catastrophic response of the kolka glacier to ice and debris loading over a period of months prior to the september 20 detachment we reconstruct the glacier debris flow using field observations in conjunction with the interpretation of seismographs from nearby seismic stations and successfully simulate the behaviour runout velocity and deposition of the post detachment glacier debris flow using a three dimensional analytical model our demonstration of a standing start hypothesis in the 2002 kolka glacier detachment has substantial implications for glacier hazard assessment and risk management strategies in valleys downstream from unstable debris covered glaciers in the mountain regions of the world

evaluating titan2d mass flow model using the 1963 little tahoma peak avalanches mount rainier washington the titan2d geophysical mass flow model is evaluated by comparing its simulation results and those obtained from another flow model flow3d with published data on the 1963 little tahoma peak avalanches on mount rainier washington the avalanches totaling approximately 10 10 6 m 3 of broken lava blocks and other debris traveled 6 8 km horizontally and fell 1 8 km vertically h l 0 246 velocities calculated from runup range from 24 to 42 m s and may have been as high as 130 m s while the avalanches passed over emmons glacier titan2d is a code for an incompressible coulomb continuum it is a depth averaged dshallow watert granular flow model the conservation equations for mass and momentum are solved with a coulomb type friction term at the basal interface the governing equations are solved on multiple processors using a parallel adaptive mesh godunov scheme adaptive gridding dynamically concentrates computing power in regions of special interest mesh refinement and coarsening key on the perimeter of the moving avalanche the model flow initiates as a pile defined as an ellipsoid by a height z and an elliptical base defined by radii in the x and y planes flow parameters are the internal friction angle and bed friction angle results from the model are similar in terms of velocity history lateral spreading location of runup areas and final distribution of the little tahoma peak deposit the avalanches passed over the emmons glacier along their upper flow paths but lower in the valley they traversed stream gravels and glacial outwash deposits this presents difficulty in assigning an appropriate bed friction angle for the entire deposit incorporation of variable bed friction angles into the model using gis will help to resolve this issue d 2004 elsevier b v all rights reserved

unraveling driving factors for large rock ice avalanche mobility large rock ice avalanches have attracted attention from scientists for decades and some of these events have caused high numbers of fatalities a relation between rock slope instabilities in cold high mountain areas and climate change is currently becoming more evident and questions about possible consequences and hazard scenarios in densely populated high mountain regions leading beyond historical precedence are rising to improve hazard assessment of potential rock ice avalanches their mobility is a critical factor this contribution is an attempt to unravel driving factors for the mobility of large rock ice avalanches by synthesizing results from physical laboratory experiments and empirical data from 64 rock ice avalanches with volumes 1x106 m3 from glacierized high mountain regions around the world the influence of avalanche volume water and ice content low friction surfaces and topography on the apparent coefficient of friction as a measure of mobility is assessed in laboratory experiments granular ice in the moving mass was found to reduce bulk friction up to 20 while water led to a reduction around 50 for completely saturated material compared with dry flows evidence for the effects of water as a key driving factor to enhance mobility was also found in the empirical data while the influence of the ice content could not be confirmed to be of much relevance in nature besides liquefaction it was confirmed that mobility increases with volumes and that frictional surface characteristics such as flow paths over glaciers are also dominant variables determining mass movement mobility effects of the topography along the flow path as well as channeling are assumed to be other critical factors the results provide an empirical basis to roughly account for different path and flow characteristics of large rock ice avalanches and to find appropriate ranges for friction parameters for scenario modeling and hazard assessments copyright 2011 john wiley sons ltd

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

a model for frictional melt production beneath large rock avalanches 1 two puzzling traits of giant rock avalanches sturzstroms are the decrease of the effective friction coefficient as a function of the volume volume effect and the remarkable preservation of large geological structures during the flow demonstrating that the upper cap of a sturzstrom travels coherently on top of a basal shear layer hence frictional heat is rapidly produced along the shear layer which could explain the formation of sheets of molten rock inside certain landslide deposits it has been conjectured that a molten layer could potentially self lubricate the base of the sturzstrom to theoretically investigate this scenario we consider the model of a rock slab sliding on an inclined surface we present a set of coupled differential equations to calculate the frictional heat produced the properties of the molten layer thickness temperature and velocity distribution and the motion of the slab our simulations illustrate the onset of self lubrication and show the volume effect when the melt viscosity is low corresponding to a simulated mafic composition of the rock for a felsic composition and to some extent also for intermediate melts we find that the melting introduces more resistance at the beginning of the melting process in close similarity with frictional melting in tectonic faults however in contrast to faults the rock avalanche is capable of overcoming the initial resistance in at least two situations if the rock is rigid and the landslide is sufficiently thick or else if the material of the landslide is disintegrated the simulations also show that although self lubrication is a viable possibility to explain the runout of sturzstroms there are rather stringent conditions for the formation of a molten layer of good lubricating qualities more generally we suggest that the properties of the coulomb frictional law at the interfaces may change radically during sliding and that the assumption of constant friction does not represent a good model in landslide calculations

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

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