HR: 1340h
AN: SA23A-1123    [Abstracts]
TI: Backscattered fraction of precipitating ionospheric photoelectrons
AU: * Richards, P G
EM: richards@cs.uah.edu
AF: George Mason University, Physics and Astronomy Department 4400 University Drive, MSN 3F3, Fairfax, VA 22030, United States
AU: Peterson, B K
EM: pete@lasp.colorado.edu
AF: LASP University of Colorado, University of Colorado 1234 Innovation Drive, Boulder, CO 80303, United States
AB: The FAST electron spectrometer offers a serendipitous opportunity to determine for the first time the fraction of precipitating photoelectrons that are backscattered. Ionospheric photoelectrons produced by solar EUV radiation can escape into the plasmasphere and travel along magnetic field lines to the opposite hemisphere. In 2002 the FAST satellite orbit sliced through the plasmasphere above 3000 km altitude where it detected photoelectrons coming from both hemispheres with energies in the range 10 to 800 eV. When one hemisphere is sunlit and the other is in darkness, the photoelectrons arriving at the satellite from the dark hemisphere are photoelectrons that are backscattered from the dark thermosphere after traveling from the sunlit hemisphere. This paper compares the measured and modeled backscattered fraction of photoelectrons. The backscatter ratio of precipitating electrons is important in relation to auroral energy deposition rate, which depends on the amount of backscattered energy flux. Direct experimental determination of auroral electron backscatter is not possible because the precipitating auroral flux is too variable in space and time.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 3300 ATMOSPHERIC PROCESSES
DE: 7514 Energetic particles (2114)
DE: 7900 SPACE WEATHER
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting