HR: 1330h
AN: SM43A-03    [Abstracts]
TI: Effects of Wave Heating and Electron Precipitation on Ion Distributions in the Dynamic Transition Region
AU: * Zeng, W
EM: zengw@uta.edu
AF: Department of Physics, the University of Texas at Arlington, Arlington, TX 76019, United States
AU: Horwitz, J L
EM: horwitz@uta.edu
AF: Department of Physics, the University of Texas at Arlington, Arlington, TX 76019, United States
AU: Tu, J
EM: Jiannan_Tu@uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, Lowell, MA 01854, United States
AB: A Dynamic Fluid Kinetic (DyFK) simulation is conducted to study the H+/O+ flows and distribution functions in the high-latitude dynamic transition region, specifically from 1000 km to 3000 km. In this case, the simulated flux tube, which extends from 120 km to 3 RE altitude, is assumed to experience 20 minutes of auroral effects, including both soft electron precipitation and transverse wave heating, and then allowed to relax in the absence of such auroral effects for another 80 minutes. In the transition region the O+ transverse thermal energy attained values up to 8 eV, while the H+ transverse temperature remained below 0.6 eV. During the presence of the auroral effects, the O+ bulk velocity increased continuously with altitude and exceeded 4 km s-1 at 3000 km altitude within 10 minutes after the initiation of the auroral effects. At least two ion distribution function types specifically associated with the transition region were seen in the simulation: (1) An H+ polar wind distribution with a downward tail or heat flux, caused by Coulomb collisions with stationary or even downward flowing O+, and (2) "Upwelling" O+ and H+ ion distributions in which the higher energy portions displayed conical features caused by transverse ion heating, while the lower energy interior cores were nearly-isotropic Maxwellians in which Coulomb self-collisions were dominant processes.
DE: 2704 Auroral phenomena (2407)
DE: 2716 Energetic particles, precipitating
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2753 Numerical modeling
DE: 2776 Polar cap phenomena
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly