Contribution of Anisotropic Electron Current to the Magnetotail Current Sheet as a Function of Location and Plasma Conditions

被引：18

作者：

Artemyev, A. V. ^{[1
,2
,3
]}

Angelopoulos, V. ^{[1
,2
]}

Vasko, I. Y. ^{[3
,4
]}

Petrukovich, A. A. ^{[3
]}

Runov, A. ^{[1
,2
]}

Saito, Y. ^{[5
]}

Avanov, L. A. ^{[6
]}

Giles, B. L. ^{[6
]}

Russell, C. T. ^{[1
,2
]}

Strangeway, R. J. ^{[1
,2
]}

机构：

[1] Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90024 USA

[2] Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA

[3] RAS, Space Res Inst, Moscow, Russia

[4] Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA

[5] Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan

[6] NASA, Goddard Space Flight Ctr, Heliophys Sci Div, Greenbelt, MD USA

来源：

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS | 2020年 / 125卷 / 01期

基金：

美国国家科学基金会;

关键词：

THIN CURRENT SHEETS; NEAR-EARTH MAGNETOTAIL; DIMENSIONAL CURRENT SHEET; PITCH-ANGLE ANISOTROPY; KINETIC ALFVEN WAVES; MAGNETIC RECONNECTION; EQUILIBRIUM STRUCTURE; CLUSTER OBSERVATIONS; FIREHOSE INSTABILITY; FIELD REVERSALS;

D O I：

10.1029/2019JA027251

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The magnetotail current sheet carries the current responsible for the largest fraction of the energy storage in the magnetotail, the magnetic energy in the lobes. It is thus inextricably linked with the dynamics and evolution of many magnetospheric phenomena, such as substorms. The magnetotail current sheet structure and stability depend mostly on the kinetic properties of the plasma populating the magnetotail. One of the most underinvestigated properties of this plasma is electron temperature anisotropy, which may contribute a large fraction of the total current. Using observations from five missions in the magnetotail, we examine the electron temperature anisotropy, T-e parallel to/T-e perpendicular to, and its potential contribution to the current density, quantified by the firehose parameter (beta(e parallel to) - beta(e perpendicular to))/2, across y is an element of [-20, 20]R-E and x is an element of [-100,-10]R-E. We find that a significant fraction (>30%) of all current sheets have an anisotropic electron current density >10% of the total current. These current sheets form two distinct groups: (1) near-Earth (<30 R-E) accompanied by weak plasma flows (<100 km/s) and enhanced equatorial magnetic field (>3 nT) and (2) middle tail (>40 R-E) accompanied by fast plasma flows (>300 km/s) and small equatorial magnetic field (<= 1 nT). For a significant number of near-Earth current sheets, the anisotropic electron current can be >25% of the total current density. Our findings suggest that electron temperature anisotropy should be included in current sheet models describing realistic magnetotail structure and dynamics.

引用

页数：14

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