[1] H. Fukunishi, Y. Takahashi, A. Uchida, M. Sera, and K. R. Miyasato. Occurrences of sprites and elves above the Sea of Japan near Hokuriku in winter. EOS Supplement, 80(46):F217, November 1999.
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To observe the rapid space-time structures of sprites and elves, we developed 16-channel array photometers using multianode photomultipliers. We operated these photometers and CCD cameras at Dodaira Astoronomical Observatory (36.0 N, 139.2 E) and Sendai(38.3N, 140.9E) in December 1998 and January 1999, and succeeded for the first time in observing sprites and elves above the Sea of Japan near the Hokuriku region in winter. These sprites and elves occurrred associated with the passage of a cold front. Since the bottom altitude of thunder clouds in winter is much lower than that in summer, it is important to investigate the characteristics of wintery sprites and elves. The two categories of sprites, column-sprites and carrot-sprites, were observed with various fine structures. The bottom and top altitudes of column-sprites observed at 1909 UT on January 27, 1999 were precisely estimated to be 73 and 87 km, respectively, on average by triagulation using simultaneous CCD camera images obtained at Dodaira and Sendai. It was also found that the vertical lengths of 13 sprite events observed on the same day range from 8 to 15 km, which are shorter than those of sprites observed in Colorado in summer. On the other hand, elves showed a spatial and temporal development similar to that observed in Colorado. The horizontal extent of elves were estimated to be 250 - 420 km. Based on these observed features, we will discuss the excitation processes of wintery sprites and elves.
[2] E A Bering, J R Benbrook, J A Garrett, A Paredes, E M Wescott, D D Sentman, H C Stenbaek-Nielsen, and W A Lyons. The 1999 sprites balloon campaign. EOS Supplement, 80(46):F216, November 1999.
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There are several competing models for the production of sprites, jets and elves. It has become clear it is not possible to select between these models using only ground-based data, owing to the fact that the ground shorts out the field signatures of interest. Consequently, a balloon campaign was conducted in June, July and August of 1999. The 1999 Sprite Balloon Campaign conducted three high altitude balloon flights, one from Palestine, Texas and two from Ottumwa, Iowa. Flight 1, an engineering test, was launched from Palestine at 01:14:31 UTC on 7/06/1999 and cutdown at 09:45:00 UTC on 07/06/1999. Flights 2 and 3 flew from Ottumwa at 23:57:30 UTC on 8/14/1999 to 12:35:00 UTC on 08/15/1999 and at 00:39:32 UTC on 08/21/1999 to 11:12:00 UTC on 08/21/99, respectively. The balloons floated at 32 km and drifted westward at ~30 knots. The balloon payloads were instrumented with dual three axis electric field detectors, three axis fluxgate and induction magnetometers, X-ray scintillation counter, Geiger-Mueller tube, upward looking high-speed photometer, vertical current density ammeter, conductivity measurements, and an ambient thermometer. A redundant telemetry scheme provided five orders of magnitude of dynamic range in sensitivity. An event triggered on-board memory sampled 10 quantities at a rate of 50 kHz per channel for 160 ms per event. Ground observations included low light level TV observations from three sites, WIRO, on Jelm Mtn., Wyoming, Bear Mtn.overlook fire tower, South Dakota, and Yucca Ridge, Colorado. Jelm Mountain had a fast photometer and a high speed TV imager. The 3rd flight was the most successful. During this flight, 304 events were recorded in the burst memory. At least half show waveforms that appear to be lightning related. All three ground stations had clear skies. There were two small sprite producing storms, one in eastern South Dakota and one in central Kansas. Perhaps as many as 20 transient luminous events were recorded by at least one station. At least four were recorded by two stations. Two of these were observed at three stations, one of which was observed by an independent fourth site. Multiple site observations of
[3] W. A. Lyons, T. E. Nelson, J. L. Eastman, R. A. Armstrong, E. R. Williams, D. S. Suszcynsky, M. A. Taylor, Y. Takahashi, E. A. Bering, and J. R. Benbrook. Sprites'99 campaign highlights and the Yucca Ridge Field Station. EOS Supplement, 80(46):F216, November 1999.
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One component of the 1999 SPRITES Campaign was conducted at the Yucca Ridge Field Station, near Ft. Collins, CO, during the months of June, July, and August 1999. The primary emphasis was providing storm forecasting and optical sprite detection during the June and August NASA stratospheric balloon missions conducted by the University of Houston (Gar Bering). On 21 August 1999 Yucca Ridge (along with several other ground stations) observed several sprites and elves above storms in South Dakota and Kansas while the NASA balloon was at 32 km over southwestern Iowa. VLF and ELF information were also obtained. This marks the first coordinated optical measurements by ground and balloon-borne sensors. A new record for sprites from a single storm occurred on the evening of 4-5 June 1999. At least 750 sprites were recorded using low-light imagers during a three-hour period above a large MCC in central South Dakota. Sprite frequencies as high as 15 per minute were noted. The storm, which may have been influenced from smoke from western wild fires, attained positive CG percentages as high as 80% at times. On 18 August 1999, a massive MCC formed as predicted over Colorado and moved slowly eastward into Nebraska. It produced extremely bright sprites, some of which were visible to the naked eye at 500+ km. Most sprites were recorded by several low light imagers and a 1000 fps high speed image intensified camera. Moreover, some of the sprites were also captured on monochrome and color conventional CCD cameras. This storm also produce clear evidence of a feature being termed a troll, a distinct jet-like structure emanating from near the cloud tops and propagating upwards to about 50 km at speeds in excess of 100 km/s, apparently along the trail of a preceding sprite tendril. For a number of sprites, additional narrow band photometric measurements of first-positive, second-positive and first negative nitrogen emissions were also obtained. Detailed cloud-scale modeling of sprite-producing storms is also underway in order to learn more about the interactions of storm dynamics, microphysics and electrification.
[4] C. P. Barrington-Leigh, U. S. Inan, and M. Stanley. Elves: Photometric and video signatures. EOS Supplement, 80(46):F216, November 1999.
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A horizontal array of fast (<30~ms resolution) photometers has proved to be an effective tool for discriminating elves (the flash in the lower ionosphere caused by heating due to the electromagnetic pulse from cloud-to-ground lightning) from other brief (~1~ms) atmospheric flashes associated with thunderstorms [Inan et al., 1997; Barrington-Leigh and Inan, 1999]. In contrast, video observations with a time resolution of 17~ms or 33~ms have presented difficulties in discriminating between sprites and elves, and have led to different conclusions about the occurrence frequency and lightning dependency of elves. Two events recorded with a 3000 frame per second intensified video system provide the first true images of elves at a frame rate appropriate for distinguishing their temporal dynamics. A 2-dimensional cylindrically symmetric electromagnetic model of the lightning-ionosphere interaction is used to relate the signatures of elves seen by photometric arrays to the luminous patches seen in some normal-speed video images, which often also contain sprites. Past observational discrepancies between video and photometry are discussed in the context of the lightning radiated electromagnetic pulses (EMP) and the quasi-electrostatic (QE) fields resulting from a lightning return stroke.
[5] L.W. Wescott, E.M. Wescott, H.C. Stenbaek-Nielsen, D.D. Sentman, D.R. Moudry, M.J. Heavner, and F.T. Sao Sabbas. Triangulation of sprites and elves from the NASA 1999 sprites balloon campaign. EOS Supplement, 80(46):F216, November 1999.
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We have recorded several thousand sprites with low light level TV systems since 1993. Sprites vary tremendously in size, from the smallest single spot of a few square km in area to huge complex forms covering several thousand square km. There have been few good opportunities to make accurate triangulations from two or three sites using similar instrumentation. Elves have not been located by triangulation. During August, 1999 the University of Alaska made optical observations from two ground sites with a baseline of 360 km. One site was on Jelm Mt. about 50 km SW of Laramie WY, and the other was on Bear Mt. near Custer WY. On four nights about 30 sprites and 10 elves were recorded by both stations in similar narrow field of view TV systems. All of the common sprite types are represented. The night of August 18 UT was the most productive, with over 20 simultaneous events. In this paper we present the results of the three dimensional triangulations of the various sprite types, and their position in space with respect to the reported NLDN CG strokes. This analysis includes details such as hot spots and typical vertical distributions. These new results are compared to previous triangulations. For the first time we are able to triangulate on the altitude and lateral size of elves events, and their location with respect to the NLDN strokes.
[6] M.G. McHarg, R.K. Haaland, D.R. Moudry, and H.C. Stenbaek-Nielsen. High speed photometric observations of sprites. EOS Supplement, 80(46):F217, November 1999.
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A high speed multi-channel photometer was built and deployed to the Wyoming Infrared Observatory (WIRO) at Mount Jelm Wyoming for the Sprites 99 campaign. The photometer records 16 channels with a 6 degree field of view at 10,000 samples per second on each channel. The photometer is bore-sighted with a high speed (1000 frames per second) imager and a narrow field low light level scene camera running at standard TV frame rates (30 frames per second). We recorded over 30 events on two nights of observations during the campaign. We report on statistical distributions of the white light optical duration of sprites as a function of sprite altitude. We also compare the results of the photometer with the high speed imager, and demonstrate that the two instruments give complimentary information. Spatial information exists on scales smaller than that of the photometer resolution, and temporal information exists at time scales shorter than the high speed imager can resolve. In combination the two instruments yield a wealth of new information about the spatial extent and temporal evolution of sprites.

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