Observations of a plasma transient on lobe field lines during a substorm. Interball Tail observations on October 3, 1995

HR: 0800h
AN: SM11A-1177 [Abstracts]
TI: Observations of a plasma transient on lobe field lines during a substorm. Interball Tail observations on October 3, 1995
AU: * Avanov, L A
EM: levon.avanov@msfc.nasa.gov
AF: National Space Science and Technology Center NASA/Marshall Space Flight Center, 320 Sparkman Dr. , Huntsville, al 35805 United States
AU: * Avanov, L A
EM: levon.avanov@msfc.nasa.gov
AF: Space Research Institute(IKI), 84/32 Profsouznaya Str, Moscow, 199182 Russian Federation
AU: Smirnov, V N
EM: vsmirnov@iki.rssi.ru
AF: Space Research Institute(IKI), 84/32 Profsouznaya Str, Moscow, 199182 Russian Federation
AU: Chandler, M O
EM: michael.o.chandler@nasa.gov
AF: National Space Science and Technology Center NASA/Marshall Space Flight Center, 320 Sparkman Dr. , Huntsville, al 35805 United States
AB: On October 3, 1995 the Interball Tail spacecraft was located in the Northern hemisphere on lobe field lines (XGSM Ś -14.8 RE, YGSM Ś -8.0 RE and ZGSMŚ 18.4 RE). Solar wind conditions monitored by the WIND and Geotail spacecrafts were quite stable with a long lasting southward magnetic field, which is favorable for formation of the plasma mantle behind the cusp region. Indeed, the Interball Tail observed a typical plasma mantle. However, at ~15:07 UT a strong plasma transient with enhanced number density up to 6-8 cm-3, velocity of ~ 400 km/s and a depressed magnetic field was detected. This transient is quite unexpected because of solar wind conditions. However, we have found that the magnetic field profile of the transient correlates well with the H component of the geomagnetic field measured by the Tixie Bay station. Ground based measurements indicate that this transient was observed a during strong substorm. We argue that this transient is probably more dense mantle plasma, which can be observed at the Interball Tail location provided that the current on the tail magnetopause is depressed. As a result the magnetic field is depressed also and the magnetic field pressure becomes less than the plasma pressure. This depression probably reflects the response of the tail magnetopause to a changing of the global current system of the magnetosphere caused by the substorm.
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2744 Magnetotail
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting