HR: 11:50h
AN: SM12B-07    [Abstracts]
TI: Timing of O+ Access to the Plasmasheet During Geomagnetic Storms
AU: * Kistler, L M
EM: Lynn.Kistler@unh.edu
AF: University of New Hampshire, Morse Hall, Durham, NH 03824,
AU: Mouikis, C G
EM: Chris. Mouikis@unh.edu
AF: University of New Hampshire, Morse Hall, Durham, NH 03824,
AU: Liao, J
EM: joy2@unh.edu
AF: University of New Hampshire, Morse Hall, Durham, NH 03824,
AU: Klecker, B
EM: berndt.klecker@mpe.mpg.de
AF: Max-Planck Institut for extraterrestriche Physic, Giessenbachstrasse, Garching, D-85748, Germany
AU: Dandouras, I
EM: Iannis.Dandouras@cesr.fr
AF: CESR, 9 Avenue Colonel-Roche, Toulouse, F-31029, France
AB: We present results of a study using CLUSTER ion composition data from the CIS instrument to study ionospheric ion access to the plasma sheet during storms. It is well known that the O+ content of the ring current increases significantly during storms. In order to get to the ring current, the ionospheric ions must first get to the plasma sheet, from where they can be convected into the ring current. Our earlier work on O+ in the plasma sheet has shown that O+ is significantly enhanced during a storm main phase. In addition we have observed that tailward moving O+ beams in the lobe, which are ions transported from the cusp, also increase during storm times. Other work has shown that the O+ outflow from the cusp increases with increased solar wind pressure. Thus one model of O+ access to the ring current would be that a pressure increase leads to enhanced outflow from the cusp. These ions are then convected into the tail lobes, enter the plasma sheet, and finally convect into the ring current. To test this model, we have identified storms which have a clear sudden increase in dynamic pressure, and have extended CLUSTER coverage in the plasma sheet and lobes. We observe the timing of when O+ enters the plasma sheet, relative to the pressure increase, and relative to the drop in Dst. Our initial results show that the O+ enters the plasma sheet about 3-5 hours after the pressure increase, and is in the plasma sheet early enough in the storm main phase to contribute to the storm-time ring current.
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2760 Plasma convection (2463)
DE: 2764 Plasma sheet
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting