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Ion density and temperature profiles along ( X GSM ) and across ( Z GSM ) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS
Author(s) -
Artemyev A. V.,
Angelopoulos V.,
Hietala H.,
Runov A.,
Shinohara I.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023710
Subject(s) - plasma sheet , physics , current sheet , magnetic reconnection , plasma , substorm , ion , lunar orbit , particle acceleration , current (fluid) , magnetic field , geophysics , atomic physics , astrophysics , magnetohydrodynamics , magnetosphere , astronomy , quantum mechanics , spacecraft , thermodynamics
Characteristics of the two‐dimensional configuration of the magnetotail current sheet are important for modeling magnetotail motion/evolution and charged particle energization. Because of the magnetotail current sheet's dynamical nature, however, simultaneous plasma and magnetic field measurements at different radial distances are required to reveal this configuration. Simultaneous observations of the magnetotail current sheet from Time History of Events and Macroscale Interactions during Substorms (THEMIS) D (around 10 R E downtail), Geotail (around 30 R E downtail), and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moons Interaction with the Sun (ARTEMIS) P1 (around 55 R E downtail) are used to study distributions of plasma (ion) density and temperature along (Earth‐Sun direction) and across (north‐south direction) the magnetotail. Fourteen events (each including several current sheet crossings at different downtail distances) are studied. We demonstrate that the plasma temperature along and across the magnetotail varies more significantly than plasma density does. The temperature decrease from equatorial plane to current sheet boundaries is a major contributor to the cross‐tail pressure balance. The Alfven velocity V A , B calculated at the current sheet boundaries increases significantly toward the Earth from 700 km/s at lunar orbit ∼55 R E to 2200 km/s around ∼10 R E downtail. The corresponding energyE A = m pV A , B 2( m p is the proton mass) is 4 times larger than the plasma temperature T 0 in the magnetotail's equatorial plane, whereas the ratio E A / T 0 is constant along the magnetotail. The plasma temperature T 0 measured around lunar orbit in the magnetotail agrees well with the simultaneously measured energy of solar wind protonsm pV SW 2 / 2 ( V SW is the solar wind speed).