HR: 0830h
AN: SH51A-08    [Abstracts]
TI: Sunward-Flowing Suprathermal Ion Populations Associated With IP Shocks
AU: * Dagen, S M
EM: dagen@space.mit.edu
AF: MIT Center for Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Kasper, J C
EM: jck@space.mit.edu
AF: MIT Center for Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Lazarus, A J
EM: ajl@space.mit.edu
AF: MIT Center for Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: Anomalous sunward-flowing suprathermal ion populations were observed from in-situ measurements made by the Wind spacecraft. These ions immediately follow certain IP shocks and can be seen for up to several hours after the shock passage. Nine such IP shock events with sunward-flowing ion number densities large enough to allow for further investigation have been identified. Numerical analysis routines aided in characterizing the particle distribution. The numerical analysis was run on all selected events using several model distribution functions. We then identified the model distribution function that best reproduced the observations. The distribution was found to be of the form of a truncated isotropic exponential function. Correlations between best-fit parameter values and magnetic field angles will be presented. The functional form of the sunward-flowing ion distribution and the parameter values will be related to macroscopic parameters of the associated shocks. The acceleration mechanisms hypothesized to be responsible for the creation of these sunward-flowing ion populations, a major aim of this investigation, will be presented. Lastly, hypotheses as to why the studied ion populations are associated with only a fraction of observed IP shocks will be discussed.
DE: 2114 Energetic particles, heliospheric (7514)
DE: 2139 Interplanetary shocks
DE: 7807 Charged particle motion and acceleration
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly