ABSTRACT

1. AE31B-0166 Ground based ISUAL validation with the Los Alamos Sferic ArrayM.J. Heavner1 W.L. Boeck2 X.M. Shao3 H.U. Frey4 S.B. Mende41Dept. Natural Sciences, University of Alaska Southeast, matt.heavner@uas.alaska.edu; 2Niagara University; 3Los Alamos National Laboratory; 4Space Sciences Laboratory, UC Berkeley INDIVIDUAL COINCIDENCES ABSTRACT ISUAL The two waveforms presented represent a strong sferic associated with the 2004/10/03 04:31:18 elves and the 2004/08/28 04:30:38 elves recorded by ISUAL. ISUAL, the imager of sprite, the upper atmospheric lightning is the secondary scientific payload on ROCSAT-2, the second satellite of the Republic of China. ISUAL consists of four components: sprite imager, spectrophotometer, array photometer, and associated electronics package. The CCD camera of the sprite imager takes 180 frames per second with 512 x 80 pixel resolution and 20 degree x 3.125 degree field of view. ISUAL has a series of filters which can be placed in front of the imager. The ISUAL events we considered for corresponding LASA observations are listed: 2004/08/12 04:30:12.340 e 2004/08/13 04:30:09.453 s 2004/08/17 04:28:29.315 e 2004/08/17 04:29:05.619 e 2004/08/18 04:28:24.329 e 2004/08/18 04:30:26.671 e 2004/08/20 04:31:13.507 e 2004/08/21 04:31:15.273 e 2004/08/26 04:30:36.245 s 2004/08/28 04:30:38.868 e 2004/08/28 04:30:49.581 e 2004/09/01 04:29:02.938 e 2004/09/01 04:29:54.593 e 2004/09/01 04:32:51.312 e 2004/10/03 04:31:18.694 e e=elves, s=sprite The Los Alamos Sferic Array (LASA) is an array of fast electric field change meters which has been used for validation studies of satellite lightning observations. The array was established to support the FORTE satellite (with both radio and optical sensors), and therefore the LASA/FORTE coincident database has been the most heavily studied. LASA has also been used to interpret and validate the observations of LIS and OTD (with optical detectors). The EDOT data set is currently being used to compliment the ROCSAT-2 ISUAL payload observations of sprites. In this presentation, we will briefly review some of the surprising results which have been documented or validated with LASA in FORTE and LIS/OTD studies, specifically the comparison of radio and optical observations of lightning. We will present a comparison of ISUAL observations with LASA electric field measurements and discuss the coincident observations based our experience with past LASA satellite validation studies. LASA has detected large discharges in association with each event. As ISUAL is limb viewing, the LASA event time compared to the ISUAL trigger times is systematically near 30ms, representing the time of flight for light of 9000 km. Many of the ISUAL events are large enough to trigger the LASA station at Los Alamos, NM, located ~2400 km from the Florida array center. This indicated these events are some of the largest occurring events (not unexpectedly). The National Lightning Detection Network (NLDN) overlaps with the LASA Florida observations. NLDN did not detect many of the ISUAL events detected by LASA. The failure of NLDN to detect many of these discharges is not unexpected. Large-amplitude sprite-producing positive cloud-to-ground discharges have been unreported by NLDN in the past. The waveforms are record by NLDN, but the first-pass algorithm of NLDN will reject some of the large peak-current discharges because they saturate many of closer NLDN stations while the more distant NLDN stations will be confused by the large ionospheric reflections present in the waveforms and trigger at the wrong time (private communication, Ken Cummins). To summarize: contrary to the misleading NLDN data, it appears that the ISUAL times are actually good, (taking into account the ~30 ms time of flight). Tigger time 2004/08/13 04:30:09.453 The above series of images are from the ISUAL imager using Filter 1 (623 - 750 nm) This filter selects the N2 1st positive band for observing sprites, while removing the 777.4 nm line which is bright in tropospheric lightning. The 760 nm airglow O2 band is also minimized. A small sprite is visible in the second to last image. The satellite view geometry.

2. SFERIC ARRAY LESSONS FROM PREVIOUS STUDIES FUTURE DIRECTIONS Los Alamos Sferic Array The Los Alamos Sferic Array (LASA) is an array of electric field change meters that utilizes Global Positioning System (GPS) receivers to provide absolute event time tagging with an accuracy of better than 50 ns. LASA has been operating since 1998 and has undergone several upgrades. During 2004 a complete overhaul was performed to take advantage of the rapid evolution of microcomputers. LASA observations presented in this poster are filtered and include the frequency range of 300 Hz to 500 kHz. LASA is focused around Florida, but includes a station in Los Alamos NM for development. Smith et al. (2001) describe the operation and instrumentation of LASA and characterize the accuracy of LASA geolocation. Part of the 2004 upgrade included an improved geolocation algorithm, presented by Harlin et al in presentation AE33A-0180. The entire EDOT upgrade is described by Shao et al in presentation AE33A-0181 and by Stanley et al in presentation AE33A-0179. TRMM/FORTE comparison The TRMM/FORTE comparison is reported by Boeck.. FORTE/LASA comparison The TRMM/FORTE comparison is reported by Boeck.. The photograph at left shows a “waysmall” computer (the white box with two black dots), a USB wireless network adaptor, a USB sound card, (with cable) and a pocket knife to indicate scale. The 400 MHz computer provides significant processing power at very low power, and is currently being evaluated for use as a SEAMONSTER node for a location with less acquisition requirements than a brick. CONCLUSIONS LASA Sprite Observations ThTRMM/FORTE comparison is reported by Boeck.. REFERENCES THANKS! Smith Abe Boeck Heavner This work would not have been possible without the help of Mark Stanley and Jeremiah Harling of Los Alamos and Rich Blakeslee of NASA Marshall Space Flight Center. Thanks! This work was partially supported by UAS.