New Aspects of the Equilibrium and Dynamics of Collisionless Current Sheets

Current sheets have huge importance for the structure and dynamics of almost all plasma systems. In space and astrophysical plasmas, they play a crucial role in many activity phenomena. Current sheets are in particular associated with the release of stored magnetic energy and its conversion into other forms of energy (e.g., kinetic energy and/or thermal energy) by processes such as magnetic reconnection.

This project will focus on current sheets in collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets).

This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas, for example to structures observed in the solar wind (see e.g., Neukirch et al., 2020).

The project will focus on open questions in and novel aspects of the theory of force-free collisionless current sheets including, but not limited to, the link between exactly neutral and quasi-neutral equilibrium current sheets, the investigation of different methods to find self-consistent collisionless force-free current sheet solutions with plasma beta values below unity (see e.g., Allanson et al., 2015,2016; Wilson et al., 2018) and the stability of such current sheets.

References: Allanson, O.D., Neukirch, T., Wilson, F. and Troscheit, S., Phys. Plasmas 22, 102116 (2015) Allanson, O.D., Neukirch, T., Troscheit, S. and Wilson, F., J. Plasma Phys. 82, 905820306 (2016) Neukirch, T, Vasko, I.Y, Artemyev, A.V. and Allanson, O.D., Astrophys. J. 891, 86 (2020) Wilson, F., Neukirch, T. and Allanson, O.D., J. Plasma Phys. 84, 905840309 (2018)