Wave and particle characteristics of earthward electron injections associated with dipolarization fronts

Abstract

[1] A comprehensive examination of particle and wave data from multiple Thermal Emission Imaging System (THEMIS) satellites has been made of an electron injection structure in the magnetotail as it propagated earthward from −20 R E to −11 R E on 27 February 2009. The electron injection, which was closely associated with a dipolarization front and bursty bulk flows, occurred within a thin plasma boundary layer and had both perpendicular and parallel energization, with very little energy dispersion. The thin plasma boundary layer had a thickness comparable to the ion inertial length and displayed different plasma characteristics at different locations. Strong electromagnetic waves between the lower hybrid frequency and the electron gyrofrequency, as well as electrostatic waves up to the electron plasma frequency, were observed within the thin plasma boundary layers. The two outermost spacecraft at X = −20.1 R E and X = −16.7 R E detected intense whistler waves, most likely driven by an observed electron temperature anisotropy with T ? /T k > 1. Closer to Earth at X = −11.1 R E , whistlers were not seen, consistent with the observed electron distribution having T ? /T k < 1. Near the electron injection region, nonlinear electrostatic structures such as electrostatic solitary waves and double layers were also observed. These nonlinear electrostatic structures can interact with the electron distribution and accelerate electrons; high energy distributions could be generated if the electrons encountered a large number of these structures. The observations show that nonideal MHD, nonlinear, and kinetic behavior is intrinsic to the electron injections with multiscale coupling.

Mesoscale PIC simulation of double layers and electron holes affecting parallel and transverse accelerations of electrons and ions

“…[63] Deng et al [2010] reported novel observations of double layers and solitary pulses in earthward electron injection events in the magnetotail from THEMIS observation. These events are associated with dipolarization of the geomagnetic field lines accompanied by bursty bulk flows of plasma.…”

Whistler mode waves at magnetotail dipolarization fronts

“…A number of case studies [Le Contel et al, 2009;Deng et al, 2010;Khotyaintsev et al, 2011;Huang et al, 2012] reported observations of whistlers in relation to DFs. In particular, they found whistlers in the magnetic flux pileup region (FPR), where the electron distribution has a perpendicular anisotropy, which is large enough to drive whistlers via the whistler anisotropy instability [Le Contel et al, 2009].…”

“…DFs are identified by a sharp increase of B z GSM and are associated with electron and ion acceleration [Asano et al, 2010;Zhou et al, 2010;Fu et al, 2011] as well as various wave activities, e.g., electron holes, whistler, lower hybrid, and electron cyclotron waves [Le Contel et al, 2009;Sergeev et al, 2009;Zhou et al, 2009;Deng et al, 2010;Khotyaintsev et al, 2011;Hwang et al, 2011].…”

Contrasting dynamics of electrons and protons in the near-Earth plasma sheet during dipolarization

“…Malykhin et al: Contrasting dynamics of electrons and protons 1992; Nakamura et al, 2002;Runov et al, 2009). DFs are associated with electron and ion acceleration (e.g., Apatenkov et al, 2007;Asano et al, 2010;Zhou et al, 2010;Fu et al, 2011;Birn et al, 2011;Grigorenko et al, 2017) as well as with various wave activities, e.g., whistler emissions, lower hybrid and electron cyclotron waves (e.g., Le Contel et al, 2009;Zhou et al, 2009;Deng et al, 2010;Khotyaintsev et al, 2011;Hwang et al, 2011;Vilberg et al, 2014;Grigorenko et al, 2016). BBFs with embedded DFs transport energy and mass from a remote tail source to the near-Earth plasma sheet (PS), where the high-speed flows are slowed down and diverted (e.g., Sergeev et al, 2009;Ge et al, 2011 and references therein).…”

“…The last may lead to additional energization and/or particles scattering and losses via processes of wave-particle interactions (e.g., Le Contel et al, 2009;Zhou et al, 2009;Deng et al, 2010;Khotyaintsev et al, 2011;Panov et al, 2013;Fu et al, 2014;Vilberg et al, 2014;Zhang and Angelopoulos, 2014;Grigorenko et al, 2016).…”