The Hall Electric Field in Earth's Magnetotail Thin Current Sheet

Abstract

One of the most important properties of Earth's magnetotail thin current sheet (TCS) is that its current is predominantly contributed by magnetized electrons. The Hall electric field, normal to the TCS and generated by charge separation, is critical to the generation of this electron current as well as a dawn‐dusk asymmetry of the magnetotail, such as duskside preference of magnetic reconnection and related structures and phenomena. However, systematic investigation of the Hall electric field has so far been lacking. Utilizing observations of TCS by Magnetospheric Multiscale and Time History of Events and Macroscale Interactions during Substorm spacecraft, we study the properties of this field. Our results, from various, complementary methods, show that the Hall electric field Ez (in the geocentric solar magnetospheric, coordinate system) or En (normal to the TCS plane) can be clearly observed to point toward the center of the current sheet. The typical magnitude of this electric field is several tenths of 1 mV/m. Statistics of Magnetospheric Multiscale magnetotail TCS crossings show that the Hall electric field is stronger on the duskside, indicating a stronger Hall effect there, which confirms predictions from global‐scale hybrid and particle‐in‐cell simulations.

Studying Dawn‐Dusk Asymmetries of Mercury's Magnetotail Using MHD‐EPIC Simulations

“…However, the Hall effect is the only mechanism that could produce dawn‐dusk asymmetry in the Hall‐A simulation, so that the Hall effect must be the reason to create higher dawnside plasma density in Hall‐A as well as the MHD‐EPIC simulations. Figure f shows that the average E z component of MHD‐EPIC‐A is stronger on the duskside, which is a key for the E × B drift explanation and is consistent with Lin et al (), Lu et al (), and Lu et al (). The MESSENGER data indicate slight proton pressure enhancement on the dawnside (Figure b), but our simulations do not show any significant preference of the proton pressure.…”

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

“…Even so, in both magnetotail regions, these anisotropic electron currents can contribute to the stress balance in the current sheet (see discussion in Artemyev et al, ), and inclusion of these currents in current sheet models can help in description of very long (stretched) current sheet configurations (with weak gradients ∂ / ∂x and strong currents). This statistical result is confirmed by several case studies successfully comparing electron current density estimates derived from the pressure anisotropy and direct electron current measurements (see Figure in Artemyev et al, and Figure in Lu et al, ).…”

Statistical properties of kinetic-scale magnetic holes in terrestrial space

“…Furthermore, the average value of positive B z on the duskside (2.6 nT) is less than on the dawnside (3.6 nT), implying that the duskside magnetic field curvature radius is smaller and its current sheet is thinner (e.g., Büchner and Zelenyi, 1989; Rong ZJ et al, 2011). This thin current sheet is considered to be generated by a stronger Hall effect on the duskside (e.g., Lu S et al, 2019). Huang SY et al (2019) also suggested that the dawn–dusk asymmetry of KSMHs in the magnetotail could be caused by the Hall effect.…”