HR: 1340h
AN: AE33A-0946    [Abstracts]
TI: Gamma Rays Above Thunderstorms: What Lightning Type is Responsible?
AU: * Williams, E R
EM: earlew@ll.mit.edu
AF: Massachusetts Institute of Technology, Parsons Laboratory Ames and Vasser Sts, Cambridge, MA 02139 United States
AU: Boldi, R
EM: bobb@ll.mit.edu
AF: MIT Lincoln Laboratory, 244 Wood St, Lexington, MA 02420 United States
AU: Bor, J
EM: satori@ggki.hu
AF: Hungarian Academy of Sciences, Geodetic and Geophysical Institute, Sopron, H-9400 Hungary
AU: Satori, G
EM: satori@ggki.hu
AF: Hungarian Academy of Sciences, Geodetic and Geophysical Institute, Sopron, H-9400 Hungary
AU: Price, C
EM: cprice@flash.tau.ac.il
AF: Tel Aviv University, Department of Geophysics and Planetary Physics, Tel Aviv, 69978 Israel
AU: Greenburg, E
EM: cprice@flash.tau.ac.il
AF: Tel Aviv University, Department of Geophysics and Planetary Physics, Tel Aviv, 69978 Israel
AU: Takahashi, Y
EM: spriteselves@yahoo.co.jp
AF: Tohuku University, Department of Geophysics, Sendai, 980-8578 Japan
AU: Yamamoto, K
EM: spriteselves@yahoo.co.jp
AF: Tohuku University, Department of Geophysics, Sendai, 980-8578 Japan
AU: Chronis, T
EM: tchronis@engr.uconn.edu
AF: University of Connecticut, Department of Environmental Engineering, Storrs, CT 06269 United States
AU: Anagnostou, E
EM: manos@hcmr.gr
AF: University of Connecticut, Department of Environmental Engineering, Storrs, CT 06269 United States
AU: Smith, D M
EM: dsmith@scipp.ucsc.edu
AF: University of California at Santa Cruz, Physics Department and Santa Cruz Institute for Particle Physics, Santa Cruz, CA 95064 United States
AU: Lopez, L
EM: astrolili@gmail.com
AF: University of California at Berkeley, Astronomy Department and Space Sciences Laboratory, Berkeley, CA 94720 United States
AB: Evidence has accrued that gamma ray bursts detected by the RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) satellite over thunderclouds are associated with lightning (Cummer et al, 2005). These lightning flashes exhibit positive polarity but vertical charge moments substantially less than the empirical threshold for sprites (>500 C-km). Further searches for lightning flashes causal to gamma ray bursts using ELF observations in Hungary, Japan, Israel and the United States confirm the unliklihood of sprite-producing lightning. A key distinction between the positive ground flashes known to produce sprites and the intracloud flashes in the main dipole of thunderclouds is the maximum altitude of lightning extent. The former flashes extend to 4-7 km whereas the latter flashes can extend to 15 km or higher. The e-folding distances for megavolt photons are of order one hundred meters in air. Calculations show that gamma rays initiated at 15 km altitude are capable of reaching the satellite at ~600 km altitude, whereas gamma rays initiated at 4-7 km altitude are greatly attenuated. Intracloud flashes with positive polarity are therefore a more likely source for the gamma radiation. The need for gamma ray initiation at high altitude is also consistent with the sparsity of RHESSI events in the extratropics, where the tropopause height and maximum cloud top heights are notably lower than in the tropics.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3359 Radiative processes
DE: 7554 X-rays, gamma rays, and neutrinos
DE: 7807 Charged particle motion and acceleration
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005