HR: 08:45h
AN: SM51A-04    [PDF]
TI: Energetic Particles And The Concept Of An Open/Closed Field Line Boundary
AU: * Fritz, T A
EM: fritz@bu.edu
AF: Center for Space Physics Boston University, 725 Commonwealth Ave., Boston, MA 02215 United States
AB: Energetic particles are often used as an indicator of the open/closed field line boundary but they are also a consistent and common feature of the high-altitude dayside cusp. Observing these particles in a region where they cannot be stably trapped is one the most striking findings of the Polar and Cluster satellites. The Polar satellite has documented that the shocked solar wind plasma enters the weak geomagnetic field of the polar region and produces cusp diamagnetic cavities (CDC) of apparent tremendous size well within the traditional magnetosphere. Within these cavities the local magnetic field is depressed and very turbulent and in many cases appears to carry the remnant signature of the upstream interplanetary magnetic field (IMF) in the two transverse components, By and Bz. The intensities of the energetic ions are observed to increase by many orders of the magnitudes during the CDC encounters. Use of the variation of the charge state of solar wind Fe ions at the ACE spacecraft and at Polar has indicated that energization of ions to these high energies is a rapid process. The charge state distribution of these cusp cavity ions is indicative of their seed populations being a mixture of the ionospheric and the solar wind particles in many cases. Although the Cluster satellites occasionally observe similar features in crossing the region of the cusp/high latitude boundary layer the features are significantly smaller and lack the close association of shocked solar wind plasma, CDCs, and energetic particles seen by Polar. Simultaneous individual case comparisons between Polar and Cluster will be presented in an attempt to resolve these differing impressions from the two data sets and the whether the concept of an open/closed field line boundary is valid in this region.
DE: 2716 Energetic particles, precipitating
DE: 2720 Energetic particles, trapped
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2740 Magnetospheric configuration and dynamics
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting