HR: 0800h
AN: AE31A-0049    [Abstracts]
TI: Energetic electron beams injected into the magnetosphere by terrestrial gamma-ray flashes
AU: * Dwyer, J R
EM: jdwyer@fit.edu
AF: Florida Institute of Technology, Department of Physics and Space Sciences 150 W. University Blvd, Melbourne, FL 32901, United States
AU: Grefenstette, B W
EM: bwgref@scipp.ucsc.edu
AF: University of California,Santa Cruz, Physics Department and Santa Cruz Institute for Particle Physics, Santa Cruz, CA 95064, United States
AU: Smith, D M
EM: dsmith@scipp.ucsc.edu
AF: University of California,Santa Cruz, Physics Department and Santa Cruz Institute for Particle Physics, Santa Cruz, CA 95064, United States
AB: We shall present evidence that at least 6 of the 36 BATSE Terrestrial Gamma-ray Flashes (TGFs) that are publicly available for analysis were produced by electron beams directly striking the spacecraft and not by gamma-rays. These electron beams, which can have energies extending above 30 MeV, form a previously unidentified population of energetic electrons in the inner magnetosphere. Recent work modeling the emission of terrestrial gamma-ray flashes as measured by the RHESSI satellite has shown that the source of TGFs is likely to be deep within the atmosphere, at altitudes ranging from about 21 km down to 15 km. As a result, the runaway electrons that create the gamma-rays via bremsstrahlung interactions with air do not escape to space from these depths. On the other hand, electrons and positions created by Compton scattering and pair-production by the gamma- rays near the top of the atmosphere can escape along the geomagnetic field lines and can be detected by orbiting spacecraft, either near the TGF or near the far conjugate point. Indeed, two of the BATSE events are found to be conjugate events originating from thousands of kilometers away from the far geomagnetic foot point. In this presentation, we will present the results of detailed Monte Carlo simulations that show that the intensities of the electron beams and the gamma-rays associated with the TGFs are similar at spacecraft altitudes and that the time-intensity profiles and anisotropy data of several BATSE events can be well fit by these simulations.
DE: 2716 Energetic particles: precipitating
DE: 3300 ATMOSPHERIC PROCESSES
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3359 Radiative processes
SC: Atmospheric and Space Electricity [AE]
MN: 2007 Fall Meeting