Coronal Heating Topology: The Interplay of Current Sheets and Magnetic Field Lines

Abstract

The magnetic topology and field line random walk properties of a nanoflare-heated and magnetically confined corona are investigated in the reduced magnetohydrodynamic regime. Field lines originating from current sheets form coherent structures, called Current Sheet Connected (CSC) regions, extended around them. CSC field line random walk is strongly anisotropic, with preferential diffusion along the current sheets' in-plane length. CSC field line random walk properties remain similar to those of the entire ensemble but exhibit enhanced mean square displacements and separations due to the stronger magnetic field intensities in CSC regions. The implications for particle acceleration and heat transport in the solar corona and wind, and for solar moss formation are discussed.

Perpendicular Transport of Energetic Particles in Magnetic Turbulence

“…in agreement with equation 8of Rechester and Rosenbluth (1978) as well as equation 4of Krommes et al (1983). This formula was also derived in Shalchi (2019b) by using arguments based on field line separation theory.…”

“…Besides the development of systematic analytical theories such as NLGC and UNLT theories, there were also attempts to describe perpendicular transport based on heuristic arguments. The most famous work in this context is the article published by Rechester and Rosenbluth (1978) with the focus on energetic particle transport in fusion plasmas. In the latter paper the importance of magnetic fields lines as well as the suppression of perpendicular transport to a sub-diffusive level due to parallel diffusion was discussed.…”

“…However, in space and astrophysical plasmas, Coulomb collision should be irrelevant and magnetic field lines should not separate exponentially. Therefore, it was often stated that Rechester and Rosenbluth (1978) does not apply in astrophysical scenarios (see, e.g., for a brief discussion of this matter). However, in Shalchi (2015a) a Rechester & Rosenbluth type of diffusion coefficient was derived from UNLT theory indicating that there is at least some connection between Rechester and Rosenbluth (1978) and energetic particle transport in space plasmas.…”

“…Therefore, it was often stated that Rechester and Rosenbluth (1978) does not apply in astrophysical scenarios (see, e.g., for a brief discussion of this matter). However, in Shalchi (2015a) a Rechester & Rosenbluth type of diffusion coefficient was derived from UNLT theory indicating that there is at least some connection between Rechester and Rosenbluth (1978) and energetic particle transport in space plasmas. In Shalchi (2019a) a heuristic approach for perpendicular transport was developed providing different formulas for the perpendicular diffusion coefficient.…”

Particle Acceleration in Relativistic Plasma Turbulence

“…4(b) show the probability density function (PDF) of the electric current density |J z,p | experienced by the particles at their injection time (normalized by the root-mean-square J z,rms in the whole domain at that time). The peak of the PDF is at |J z,p | ∼ 4 J z,rms , and ∼ 95% of the injected particles reside at |J z,p | > 2 J z,rms , a threshold that is usually employed to identify current sheets [59]. This should be contrasted with the blue diamonds, showing the PDF of the electric current experienced by our tracked particles at ct/l = 4, regardless of whether they are injected or not.…”