HR: 1340h
AN: SM43C-1240    [Abstracts]
TI: Investigation of the Cusp Energetic Ions Using a Global Hybrid Simulation
AU: * Wang, X
EM: xywang@physics.auburn.edu
AF: Auburn University, 206 Allison Laboratory, Auburn, AL 36849 United States
AU: Lin, Y
EM: ylin@physics.auburn.edu
AF: Auburn University, 206 Allison Laboratory, Auburn, AL 36849 United States
AU: Chang, S
EM: changs@cspar.uah.edu
AF: University of Alabama in Huntsville, Center for Space Plasma and Aeronomic Research, Huntsville, AL 35899 United States
AB: It has been suggested by satellite observations that energetic (10¹ - 10² KeV) ions in the magnetospheric cusp are originated from the quasi-parallel bow shock. In this study, a 3-D global-scale hybrid simulation is carried out to investigate the ion signature and ion energization in the cusp regions of the magnetosphere. The simulation is shown for cases in which the IMF geometry leads to the inter-connection between the field lines in the northern cusp and those in the quasi-parallel bow shock through a high-latitude reconnection. The IMF and solar wind conditions are kept constant in each case. First, ion velocity distributions are examined for the foreshock region. Accelerated, backstreaming ions are found in the foreshock of the quasi-parallel shock. The foreshock ions possess a diffuse ion distribution with a non-thermal spectral break at energy ~ 15-30KeV for cases with Mach number M_A =5-9, and the differential ion flux evolves with the field-aligned distance to the bow shock by an e-folding distance of 3-9 R_E at various energy channels, consistent the satellite observation. Second, the coupling between the particle signatures in the foreshock and the cusp is investigated. The energetic ions (up to ~ 10² KeV) are also present downstream of the shock, through the magnetosheath to the cusp vicinity, with a spectral break similar to that in the foreshock. The distributions in the cusp boundary show the presence of two ion populations: a population of the local cusp proper and an ion beam from the magnetosheath. Our simulation indicates a strong coupling between the energetic ions at the quasi-parallel shock and the cusp energetic ions. Third, Alfvén waves are found to be generated in the magnetosphere due to the foreshock pressure pulses, and due to magnetic reconnection at the magnetopause. The influence of the waves on the cusp magnetosphere is discussed. The results will also be compared with the cases in which the IMF is also northward but the bow shock is dominated by a quasi-perpendicular shock.
DE: 2154 Planetary bow shocks
DE: 2706 Cusp
DE: 2716 Energetic particles: precipitating
DE: 2753 Numerical modeling
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005