HR: 17:15h
AN: AE14A-06    [Abstracts]
TI: A View From Above: TGFs From Space.
AU: * Colman, J J
EM: jonah@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D401, Los Alamos, NM 87545 United States
AU: Roussel-Dupre, R A
EM: rroussel-dupre@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D401, Los Alamos, NM 87545 United States
AU: Symbalisty, E M
EM: esymbalisty@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D401, Los Alamos, NM 87545 United States
AB: The expected signal from a terrestrial gamma ray flash (TGF) at a satellite detector is calculated. The satellite is assumed to operate at a height of 800 km and the detector is assumed to be sensitive in the range of 10 keV to 40 MeV. A high altitude discharge is simulated from first principles, using a model incorporating relativistic runaway breakdown and a fully self-consistent electric field. This model extends from the ground to 90 km and incorporates a strong convective system with a cloud top near 15 km. The cloud is initially charged and the atmospheric column allowed to come to electrostatic equilibrium. An inter-cloud discharge is simulated by adding the opposite charge distribution to the cloud over a finite time. This results in the creation of an electric field in the atmosphere above the cloud. Seed electrons are added continuously within the spatial grid, simulating the influence of cosmic rays. An upward moving runaway discharge is thus created and it in turn generates a sprite (i.e. electromagnetic output) between 15 and 30 km. This sprite is considered to be the source of a TGF. The electromagnetic output is generated as a function of photon momentum, spatial location, and time. It is propagated to a receiver at an altitude of 800 km (the satellite). A full radiative transfer treatment is performed employing the Klein-Nishina differential cross sections for Compton interactions based on the average Z number of air. Compton scattering and absorption are included as well as electron positron pair production. Photons are allowed to scatter both into and out of the satellite field of view. The signal at the detector is then generated as a function of photon momentum and time.
DE: 2720 Energetic particles: trapped
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005