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Magnetotail Structure and its Internal Particle Dynamics During Northward IMFThis study uses Global magnetohydrodynamic (MHD) simulations driven by solar wind data along with Geotail observations of the magnetotail to investigate the magnetotail's response to changes in the interplanetary magnetic field (IMF); observed events used in the study occurred on March 29, 1993 and February 9, 1995. For events from February 9, 1995, we also use the time-dependent MHD magnetic and electric fields and the large-scale kinetic (LSK) technique to examine changes in the Geotail ion velocity distributions. Our MHD simulation shows that on March 29, 1993, during a long period of steady northward IMF, the tail was strongly squeezed and twisted around the Sun-Earth axis in response to variations in the IMF B(sub y) component. The mixed (magnetotail and magnetosheath) plasma observed by Geotail results from the spacecraft's close proximity to the magnetopause and its frequent crossings of this boundary. In our second example (February 9, 1995) the IMF was also steady and northward, and in addition had a significant B(sub y) component. Again the magnetotail was twisted, but not as strongly as on March 29, 1993. The Geotail spacecraft, located approximately 30 R(sub E) downtail, observed highly structured ion distribution functions. Using the time-dependent LSK technique, we investigate the ion sources and acceleration mechanisms affecting the Geotail distribution functions during this interval. At 1325 UT most ions are found to enter the magnetosphere on the dusk side earthward of Geotail with a secondary source on the dawn side in the low latitude boundary layer (LLBL). A small percentage come from the ionosphere. By 1347 UT the majority of the ions come from the dawn side LLBL. The distribution functions measured during the later time interval are much warmer, mainly because particles reaching the spacecraft from the dawn side are affected by nonadiabatic scattering and acceleration in the neutral sheet.
Document ID
19990078588
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Ashour-Abdalla, M.
(California Univ. Los Angeles, CA United States)
Raeder, J.
(California Univ. Los Angeles, CA United States)
El-Alaoui, M.
(California Univ. Los Angeles, CA United States)
Peroomian, V.
(California Univ. Los Angeles, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Publication Information
Publication: New Perspectives on the Earth's Magnetotail
Publisher: American Geophysical Union
Subject Category
Geophysics
Report/Patent Number
Geophysical-Monograph-105
IGPP-UCLA-Publ-4934
Funding Number(s)
CONTRACT_GRANT: NAGw-4553
CONTRACT_GRANT: NAG5-1100
Distribution Limits
Public
Copyright
Other

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