Plasma Transport in the Earth's Magnetotail
- Gordon R. Wilson
Published Online: 18 MAR 2013
Copyright 1991 by the American Geophysical Union.
Modeling Magnetospheric Plasma Processes
How to Cite
Lui, A. T. Y. (1991) Plasma Transport in the Earth's Magnetotail, in Modeling Magnetospheric Plasma Processes (ed G. R. Wilson), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM062p0041
- Published Online: 18 MAR 2013
- Published Print: 1 JAN 1991
Print ISBN: 9780875900285
Online ISBN: 9781118663905
- Space plasmas—Mathematical models—Congresses;
- Magnetosphere—Mathematical models—Congresses
An accurate assessment of plasma transport within and across the various plasma domains of the magnetotail is essential in the development of a global magnetospheric model. We summarize here the observed transport in the magnetotail during geomagnetic quiet and substorm periods. We note that the transport characteristics of magnetotail domains, determined to a great extent by the entry of solar wind and ionospheric plasmas to the magnetotail, are modulated by the solar and geomagnetic activities. During quiet conditions, plasma transport in the distant tail (>100 RE downstream) is dominated by tailward flowing plasma originated from the solar wind. However, the traditional idea of the tail region closer in being populated mostly by plasma of solar wind origin (transported earthward from the distant tail region) is now in question since it grossly underestimates the strengths of the ionospheric sources. The neglect of upwelling ionospheric plasmas in previous magnetotail studies has also contributed to much confusion in the determination of plasma transport associated with plasma sheet thinning during the substorm expansion phase. Comprehensive studies have now revealed that plasma transport in the central plasma sheet within ∼ 20 RE downstream is almost exclusively sunward and that fast plasma transport (>400 km/s in speed) within the plasma sheet is basically infrequent and transient (mostly lasting for <1 min), even during highly disturbed geomagnetic conditions. This characteristic may be intrinsic to the true nature of the substorm process; the substorm expansion phase may well be a conglomeration of transient substorm intensifications, much like lightning in a thunderstorm. Finally, we emphasize that a complete picture of plasma transport within the magnetotail relies to some extent on future ability to provide accurate measurements of the very low-energy (<50 eV) part of the plasma population which is directly traceable to ionospheric sources.