Study of the Electron Velocity Inside Sub‐Ion‐Scale Magnetic Holes in the Solar Wind by MMS Observations

Abstract

Electron vortices are a key element in the sub-ion magnetic hole. Here, we investigate the electron velocity inside two sub-ion magnetic holes in the solar wind based on the Magnetospheric Multiscale (MMS) mission. We find that the observational electron velocities inside the magnetic holes are contributed by the combination of the electron diamagnetic (V e,dia), E × B (V e,E), magnetic gradient (V e,▽B) and curvature (V e,R) drifts. V e,dia , V e,▽B , and V e,R are comparable, while V e,E is very small inside the hole. The weak V e,E could result from the electric field approximately perpendicular to the magnetic field inside the structure. The value of V e,▽B + V e,R is near 0; thus, V e,dia is approximately equal to the observational electron velocity. The current density contributed by the electron diamagnetic, magnetic gradient and curvature drift motions is self-consistent with the magnetic depression inside the hole, suggesting that these three electron drift motions play a crucial role in stabilizing the magnetic hole in the mirror-stable astrophysical plasma environment.

Statistical properties of kinetic-scale magnetic holes in terrestrial space

“…Train‐like KSMHs were observed in the solar wind, and clear evidence indicated that they were electron mirror mode structures (Yao ST et al, 2019b). The generation, geometry, and particle behaviors of the solar wind KSMHs were further studied by Wang GQ et al (2020b, c, d).…”

High-precision Calibration of the Fluxgate Magnetometer Offset Vector in the Terrestrial Magnetosheath

“…In recent decades, electron-scale magnetic dips are reported to widely exist in the terrestrial current sheet (Ge et al 2011;Shustov et al 2019;Yao et al 2021), planetary magnetosheaths (Huang et al 2017;Goodrich et al 2021;Wu et al 2021), and solar wind (Wang et al 2020a(Wang et al , 2020b(Wang et al , 2021d. And electron-scale magnetic peaks are also revealed to exist in the terrestrial magnetosheath (Yao et al 2018) and solar wind (Wang et al 2021c.…”

Electron-scale Magnetic Peaks Upstream of Mercury’s Bow Shock: MESSENGER Observations

“…In the last decade, electron-scale magnetic holes (ESMHs) are reported to widely exist in the terrestrial magnetotail current sheet (Ge et al 2011;Sun et al 2012), planetary magnetosheaths (Goodrich et al 2021;Wu et al 2021;Chen et al 2022), and solar wind (Wang et al 2020a(Wang et al , 2020b(Wang et al , 2021a. Their spatial sizes are generally less than 1 ρ i (ion gyroradius), though some of them have sizes up to 2 ρ i (Sun et al 2012;Wang et al 2020c).…”

“…Their spatial sizes are generally less than 1 ρ i (ion gyroradius), though some of them have sizes up to 2 ρ i (Sun et al 2012;Wang et al 2020c). Bipolar features are often observed in the electron velocity inside ESMHs, suggesting the existence of electron vortices inside them (Wang et al 2020a(Wang et al , 2020b. ESMHs can trap electrons (Sun et al 2012), and abundant wave activities could occur inside them (Yao et al 2019a).…”