GEOTAIL OBSERVATIONS OF PLASMA SHEET CONVECTION DURING DIFFERENT 
STATES OF THE MAGNETOSPHERE

Eija I. Tanskanen
SEC seminar at Goddard SFC, Friday April 30, 2004 at noon

Earth's magnetotail responds to strong solar wind driving in several 
different ways; southward IMF Bz can lead to isolated magnetotail 
loading-unloading (substorms), periodic loading-unloading, or steady 
magnetospheric convection (SMC). However, it is not known how steady 
the entire magnetotail and particularly plasma sheet is during 
different convection states. We surveyed 1.5 years of Geotail data 
(Nov through Apr, from 1999 to 2002), examining total pressure 
changes in the magnetotail during prolonged periods (>8h) of 
southward interplanetary magnetic field z-component. We searched 
answers to following questions (I) How the tail responds to extended 
intervals of IMF Bz < 0? (II) What the relative occurrence rates are 
for the steady total pressure intervals we label continuous 
magnetospheric dissipation (CMDs) and for the intervals of 
loading-unloading? (III) How steady are magnetotail and plasma sheet 
during CMD, and what is the occurrence rate for extremely steady 
intervals, SMCs? (IV) What kind of IMF Bz profiles give rise to 
different convection modes? (V) Are there any parameters at the solar 
wind that can be used to predict the state of tail convection?