HR: 0800h
AN: SM31A-09    [Abstracts]
TI: The Quiet Time Ionospheric Source of Ring Current Plasmas in Boundary Related Coordinates
AU: * Peterson, W
EM: Bill.Peterson@lasp.colorado.edu
AF: LASP, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303, United States
AU: Andersson, L
EM: laila.andersson@lasp.colorado.edu
AF: LASP, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303, United States
AU: Collin, H
EM: fortimas@znet.com
AF: Lockheed Martin Advanced Technology Center, 3251 Hanover St, Palo Alto, CA , United States
AU: Scudder, J
EM: jds@space-theory.physics.uiowa.edu
AF: Dept of Physics and Astronmy, University of Iowa, Iowa City, IA , United States
AB: Almost all of the ring current plasma comes from the plasma sheet, which is in turn supplied by the ionosphere and solar wind. We know that O+ ions from the ionosphere are present in all regions of the magnetosphere at low levels even during geomagnetically quiet intervals. We also know heavy ionospheric ions such as O+ play a role in the evolution of geomagnetic storms, but we are not sure exactly what that role is. Large-scale modeling efforts constrained by observations provide the fastest path forward to increasing our understanding. One of the obstacles to effectively using the extensive information about ion outflow to constrain large-scale magnetospheric models has been the lack of information about the distribution of the ion outflow in relation to large-scale magnetospheric features such as the auroral oval. We have used data from the Polar satellite to determine the average number and energy fluxes of escaping energetic (15 eV < E/q < 33 keV) H+ and O+ ions in boundary related coordinates during geomagnetically quiet times (Dst < -50). The characteristic energy of escaping ions is determined from the ratio of energy and number fluxes. During quiet times, we found that the characteristic energies in the dayside and nightside auroral regions were moderately uniform. Characteristic O+ energies in the dayside and night side auroral zones are 120 and 700 eV respectively. For H+ the energies are 280 eV and 1.2 keV respectively. We found the most energetic and variable characteristic energies in the polar cap region. Comparison with other observations, including those of thermal O+ from Akebono show that the escaping energetic fluxes in the polar cap are a small fraction (2-3%) of those escaping from the auroral zone. If energization processes acting on auroral field lines above our 1 RE observational altitude are important only during geomagnetic storm intervals, the data presented here almost completely characterize the magnetosphere's ionospheric plasma source during geomagnetically quiet times thus providing an important constraint on large-scale magnetospheric models including mass composition that are in development.
DE: 2764 Plasma sheet
DE: 2778 Ring current
DE: 7846 Plasma energization
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly