In a magnetized, collisionless plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase in the magnetic-field strength in such a plasma hence leads to an increase in the thermal pressure perpendicular to the field lines. Above a $$\unicode[STIX]{x1D6FD}$$-dependent threshold (where $$\unicode[STIX]{x1D6FD}$$ is the ratio of thermal to magnetic pressure), this pressure anisotropy drives the mirror instability, producing strong distortions in the field lines on ion-Larmor scales. The effect of this instability on magnetic reconnection is investigated using a simple analytical model for the formation of a current sheet (CS) and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a CS in a collisionless plasma, coupled with the low threshold for the mirror instability in a high-$$\unicode[STIX]{x1D6FD}$$plasma, imply that the geometry of reconnecting magnetic fields can differ radically from the standard Harris-sheet profile often used in simulations of collisionless reconnection. Because of this, depending on the rate of CS formation and the initial CS thickness, tearing modes whose growth rates and wavenumbers are boosted by this difference may disrupt the mirror-infested CS before standard tearing modes can develop. A quantitative theory is developed to illustrate this process, which may find application in the tearing-mediated disruption of kinetic magnetorotational ‘channel’ modes.
Alt, Andrew and Kunz, Matthew W.. "Onset of magnetic reconnection in a collisionless, high-β plasma." Journal of Plasma Physics, vol. 85, no. 1, Feb. 2019. https://doi.org/10.1017/S0022377819000084
Alt, Andrew, & Kunz, Matthew W. (2019). Onset of magnetic reconnection in a collisionless, high-β plasma. Journal of Plasma Physics, 85(1). https://doi.org/10.1017/S0022377819000084
Alt, Andrew, and Kunz, Matthew W., "Onset of magnetic reconnection in a collisionless, high-β plasma," Journal of Plasma Physics 85, no. 1 (2019), https://doi.org/10.1017/S0022377819000084
@article{osti_1547059,
author = {Alt, Andrew and Kunz, Matthew W.},
title = {Onset of magnetic reconnection in a collisionless, high-β plasma},
annote = {In a magnetized, collisionless plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase in the magnetic-field strength in such a plasma hence leads to an increase in the thermal pressure perpendicular to the field lines. Above a $\unicode[STIX]{x1D6FD}$-dependent threshold (where $\unicode[STIX]{x1D6FD}$ is the ratio of thermal to magnetic pressure), this pressure anisotropy drives the mirror instability, producing strong distortions in the field lines on ion-Larmor scales. The effect of this instability on magnetic reconnection is investigated using a simple analytical model for the formation of a current sheet (CS) and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a CS in a collisionless plasma, coupled with the low threshold for the mirror instability in a high-$\unicode[STIX]{x1D6FD}$plasma, imply that the geometry of reconnecting magnetic fields can differ radically from the standard Harris-sheet profile often used in simulations of collisionless reconnection. Because of this, depending on the rate of CS formation and the initial CS thickness, tearing modes whose growth rates and wavenumbers are boosted by this difference may disrupt the mirror-infested CS before standard tearing modes can develop. A quantitative theory is developed to illustrate this process, which may find application in the tearing-mediated disruption of kinetic magnetorotational ‘channel’ modes.},
doi = {10.1017/S0022377819000084},
url = {https://www.osti.gov/biblio/1547059},
journal = {Journal of Plasma Physics},
issn = {ISSN 0022-3778},
number = {1},
volume = {85},
place = {United States},
publisher = {Cambridge University Press},
year = {2019},
month = {02}}
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, Vol. 236, Issue 1204, p. 112-118https://doi.org/10.1098/rspa.1956.0116