A statistical study of kinetic‐size magnetic holes in turbulent magnetosheath: MMS observations

Abstract

Kinetic‐size magnetic holes (KSMHs) in the turbulent magnetosheath are statistically investigated using high time resolution data from the Magnetospheric Multiscale mission. The KSMHs with short duration (i.e., <0.5 s) have their cross section smaller than the ion gyroradius. Superposed epoch analysis of all events reveals that an increase in the electron density and total temperature significantly increases (resp. decrease) the electron perpendicular (resp. parallel) temperature and an electron vortex inside KSMHs. Electron fluxes at ~90° pitch angles with selective energies increase in the KSMHs are trapped inside KSMHs and form the electron vortex due to their collective motion. All these features are consistent with the electron vortex magnetic holes obtained in 2‐D and 3‐D particle‐in‐cell simulations, indicating that the observed KSMHs seem to be best explained as electron vortex magnetic holes. It is furthermore shown that KSMHs are likely to heat and accelerate the electrons.

Observations of a Kinetic‐Scale Magnetic Hole in a Reconnection Diffusion Region

“…Many features of this electron vortex MH are similar to those of the electron vortex MHs reported in previous numerical simulations and observations in the turbulent magnetosheath (Haynes et al, 2015;Huang, Du, et al, 2017;Roytershteyn et al, 2015). To the best of our knowledge, this is the first observation of MH in reconnection diffusion region.…”

“…The electron bulk velocity V eN reverses from −400 km/s to 400 km/s (Figure 2c). This is a typical signature of electron vortex in the L-N plane, which have been reported in kinetic-scale MHs both in observations and simulation (Haynes et al, 2015;Huang, Du, et al, 2017;Yao et al, 2017). This electron vortex formed a current loop, which is manifested as the bipolar J N (Figure 2d).…”

“…These include the electron mirror mode or field-swelling instability (Gary & Karimabadi, 2006;Pokhotelov et al, 2013), solitary waves (Ji et al, 2014;Li et al, 2016;Stasiewicz et al, 2003;Yao et al, 2017), decaying turbulence (Haynes et al, 2015;Huang, Du, et al, 2017;Roytershteyn et al, 2015), and electron Kelvin-Helmholtz instability (Pritchett & Mozer, 2009). These include the electron mirror mode or field-swelling instability (Gary & Karimabadi, 2006;Pokhotelov et al, 2013), solitary waves (Ji et al, 2014;Li et al, 2016;Stasiewicz et al, 2003;Yao et al, 2017), decaying turbulence (Haynes et al, 2015;Huang, Du, et al, 2017;Roytershteyn et al, 2015), and electron Kelvin-Helmholtz instability (Pritchett & Mozer, 2009).…”

“…It has been widely observed in various space plasmas, including the solar wind (Turner et al, 1977;Winterhalter et al, 1995;Zhang et al, 2008), the comet magnetosphere (Russell et al, 1987), the planetary magnetosheath (Balikhin et al, 2009;Cattaneo et al, 1998;Huang, Du, et al, 2017;Joy et al, 2006;Lucek et al, 1999;Tsurutani et al, 1982;Violante et al, 1995), and the magnetosphere (Ge et al, 2011;Gershman et al, 2016;Shi et al, 2009;Sun et al, 2012;Zhang et al, 2017). It has been widely observed in various space plasmas, including the solar wind (Turner et al, 1977;Winterhalter et al, 1995;Zhang et al, 2008), the comet magnetosphere (Russell et al, 1987), the planetary magnetosheath (Balikhin et al, 2009;Cattaneo et al, 1998;Huang, Du, et al, 2017;Joy et al, 2006;Lucek et al, 1999;Tsurutani et al, 1982;Violante et al, 1995), and the magnetosphere (Ge et al, 2011;Gershman et al, 2016;Shi et al, 2009;Sun et al, 2012;Zhang et al, 2017).…”

“…Subion scale MHs have been observed both in steady and turbulent plasmas (Gershman et al, 2016;Huang, Du, et al, 2017;Yao et al, 2017;Zhang et al, 2017). Subion scale MHs have been observed both in steady and turbulent plasmas (Gershman et al, 2016;Huang, Du, et al, 2017;Yao et al, 2017;Zhang et al, 2017).…”