HR: 14:02h
AN: SM23B-02    [Abstracts]
TI: State of the Magnetotail: Steady and Bursty Magnetospheric Convection
AU: * Tanskanen, E I
EM: eija.tanskanen@gsfc.nasa.gov
AF: E.I. Tanskanen, NASA GSFC, Greenbelt, MD 20771 United States
AU: Slavin, J A
AF: E.I. Tanskanen, NASA GSFC, Greenbelt, MD 20771 United States
AB: Geotail and Cluster observations are used to examine the state of the Earth's magnetotail. In this paper we are particularly interested about the plasma sheet convection and the tail "stress level". Tail static pressure (magnetic + thermal pressure) is used to characterize different convection modes, and earthward bulk velocity is used to identify burstyness of the plasma sheet. Four basic convection modes are identified: loading, unloading, steady magnetospheric convection (SMC) and continuous magnetospheric dissipation (CMD). Bulk ion velocity is used to characterize the nature of the convection in the plasma sheet during each of these states. Bursty bulk flows (BBFs) were found to be basic building blocks of the all the tail states. When solar wind drives magnetosphere over several substorm cycle (> 8 hours) the plasma sheet was observed to be highly active and non-steady. The tail stress level was studied by using magnetic and plasma measurements from four Cluster spacecraft. Tail total current was computed, and x-component of the J cross B was used as a "tail stress index". Examples of slightly and strongly stretched magnetotail will be presented and the validity of the tail stress index will be evaluated.
DE: 2744 Magnetotail
DE: 2760 Plasma convection
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting