Equilibrium Configurations of Super‐Thin Current Sheets in Space Plasma: Characteristic Scaling of Multilayer Structures

Abstract

Thin current sheets (TCSs) are the key structures in space and laboratory plasmas responsible for the accumulation and subsequent release of the stored magnetic energy. Spacecraft measurements in the near Earth's space revealed the complicated multilayer TCSs structure consisting from extremely thin and strong electron current embedded inside the thicker ion current layer. In this paper we present for the first time the analytical self‐consistent model of 1D super thin electron current sheet (STCS) supported by magnetized electrons within a much wider (but still very thin) proton structure carried by nonmagnetized (quasi‐adiabatic) particles. We take into account the dependence of electron STCS on anisotropy of electron distribution and magnetic field shear often existing in realistic TCS configurations. It is shown that the structure of the embedded STCS can be described by the simple nonlinear equation, which allows to estimate the scaling of STCS thickness due to coupling of electron and ion domains, although electron dynamics described by guiding center drift approximation is scale free. The theoretical results are in a good agreement with MMS spacecraft observations in the Earth's magnetotail.

Force‐Free Current Sheets in the Jovian Magnetodisk: The Key Role of Electron Field‐Aligned Anisotropy

“…Formation of such 1D current sheets around the fire‐hose marginally stability threshold has been predicted theoretically (e.g., Cowley, 1978; Cowley & Pellat, 1979; Francfort & Pellat, 1976), but never have been detected under quiet geomagnetic conditions in the Earth's magnetotail (see discussion in Artemyev & Zelenyi, 2013; Sitnov et al., 2006). Observations of these current sheets in the Jovian magnetotail confirm the theoretical predictions, which can further lead to improved current sheet models (see discussion on development of the next generation of current sheet models in Y. D. Yoon et al., 2021; Y. D. Yoon et al., 2023; Zelenyi et al., 2022).…”

“…Observations of these current sheets in the Jovian magnetotail confirm the theoretical predictions, which can further lead to improved current sheet models (see discussion on development of the next generation of current sheet models in Y. D. Yoon et al, 2021;Y. D. Yoon et al, 2023;Zelenyi et al, 2022).…”

“…These streams contribute to the field-aligned electron anisotropy, A e > 1, and fire-hose parameter Λ e > 0. In typical thick current sheets such anisotropy supports the cross-field electron currents (see Equation 1) and may create a thin, sub-ion scale current sheet embedded into a thick, ion scale current sheet (e.g., Kamaletdinov et al, 2020;Mingalev et al, 2018;Zelenyi et al, 2004Zelenyi et al, , 2022. Indeed, the magnetic field profiles in Figure 5 exhibit stronger gradients around B l ∼ 0.…”

Nonlinear Equilibrium Structure of Super Thin Current Sheets: Influence of Quasi‐Adiabatic Electron Population

“…Thus MMS data in the Earth's magnetotail considered by our group of experimenters demonstrated the possibility of the formation of the newest class of quasi-equilibrium current sheet configurations, STCS, where demagnetized quasi-adiabatic electrons and protons coexist in CS plasma environment together with the magnetized electron population. Such equilibria are different from the ones with totally magnetized electrons in TCS discussed in our earlier publications (Zelenyi et al, 2004a(Zelenyi et al, , 2011(Zelenyi et al, , 2020(Zelenyi et al, , 2022, and ones with totally demagnetized electrons near the magnetotail X-lines (Hoshino et al, 1996;Runov et al, 2003). The multitude of scales of CS structures due to different dynamics of protons and various parts of electron populations can be a reason of CS peculiarities, that required the theoretical background and advanced experimental studies.…”

Kinetic Equilibrium of Two-dimensional Force-free Current Sheets

“…The latter solution has multiple variants, most of which are devoted to the construction of quasi-1D current sheets with B n ≠ 0 and ∇ l ≈ 0. Such currentsheet models aim to describe equilibria of planetary magnetospheres (see discussion in Sitnov et al 2006;Zelenyi et al 2011Zelenyi et al , 2022Sitnov & Arnold 2022) that often demonstrate a need for anisotropy contribution in the stress balance (see discussion in Sitnov et al 2019;Artemyev et al 2021). Moreover, nonlinear dynamics of large-amplitude Alfvén waves in the solar wind and the subsequent formation of rotational discontinuities (e.g., Medvedev & Diamond 1996;Medvedev et al 1997;Vasquez & Hollweg 1998, 1999 may also be affected by plasma anisotropy (e.g., Tenerani et al 2017;Tenerani & Velli 2018), with observable effects on discontinuity configuration (see, e.g., discussion in Artemyev et al 2020, and references therein).…”