HR: 1340h
AN: SA23A-0388    [Abstracts]
TI: Study of the Proton Arc Spreading Effect on Ionization Rates
AU: * Fang, X
EM: xhfang@umich.edu
AF: Space Physics Research Laboratory, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48105 United States
AU: Liemohn, M W
EM: liemohn@umich.edu
AF: Space Physics Research Laboratory, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48105 United States
AU: Kozyra, J U
EM: jukozyra@umich.edu
AF: Space Physics Research Laboratory, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48105 United States
AU: Solomon, S C
EM: stans@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 United States
AB: We investigate the influence of the beam spreading effect in a proton auroral arc on resulting ionization rates, using our three-dimensional Monte Carlo ion precipitation model. A proton arc with a Maxwellian energy spectrum has two dimensions at the top level of 950 km altitude: an infinite extent in the east-west direction and a limited width in the north-south direction. Two types of incident energy flux distribution, a homogeneous and a Gaussian distribution, are imposed. The spreading effect due to charge exchange/electron stripping collisions are numerically simulated in both vertical and tilted magnetic field lines. The results of model calculations show that a single attenuation coefficient introduced in one-dimensional theoretical models as a simplification to the beam spreading effect can not completely solve the problem. In contrast, ionization rates are overestimated at high altitudes but underestimated at low altitudes. These findings can help to better understand calculation results when using simplified 1-D models.
DE: 7843 Numerical simulation studies
DE: 2407 Auroral ionosphere (2704)
DE: 2455 Particle precipitation
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting