Thin current sheets in collisionless plasma: Equilibrium structure, plasma instabilities, and particle acceleration

Journal Article · Tue Feb 15 04:00:00 EST 2011 · Plasma Physics Reports

DOI:https://doi.org/10.1134/S1063780X1102005X· OSTI ID:22047555

Zelenyi, L M; Malova, H V; Artemyev, A V; Popov, V Yu; Petrukovich, A A ^[1]

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1. Russian Academy of Sciences, Space Research Institute (Russian Federation)

The review is devoted to plasma structures with an extremely small transverse size, namely, thin current sheets that have been discovered and investigated by spacecraft observations in the Earth's magnetotail in the last few decades. The formation of current sheets is attributed to complicated dynamic processes occurring in a collisionless space plasma during geomagnetic perturbations and near the magnetic reconnection regions. The models that describe thin current structures in the Earth's magnetotail are reviewed. They are based on the assumption of the quasi-adiabatic ion dynamics in a relatively weak magnetic field of the magnetotail neutral sheet, where the ions can become unmagnetized. It is shown that the ion distribution can be represented as a function of the integrals of particle motion-the total energy and quasi-adiabatic invariant. Various modifications of the initial equilibrium are considered that are obtained with allowance for the currents of magnetized electrons, the contribution of oxygen ions, the asymmetry of plasma sources, and the effects related to the non-Maxwellian particle distributions. The theoretical results are compared with the observational data from the Cluster spacecraft mission. Various plasma instabilities developing in thin current sheets are investigated. The evolution of the tearing mode is analyzed, and the parameter range in which the mode can grow are determined. The paradox of complete stabilization of the tearing mode in current sheets with a nonzero normal magnetic field component is thereby resolved based on the quasi-adiabatic model. It is shown that, over a wide range of current sheet parameters and the propagation directions of large-scale unstable waves, various modified drift instabilities-kink and sausage modes-can develop in the system. Based on the concept of a turbulent electromagnetic field excited as a result of the development and saturation of unstable waves, a mechanism for charged particle acceleration in turbulent current sheets is proposed and the energy spectra of the accelerated particles are obtained.

• OSTI ID: 22047555
• Journal Information: Plasma Physics Reports, Journal Name: Plasma Physics Reports Journal Issue: 2 Vol. 37; ISSN PPHREM; ISSN 1063-780X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ASTROPHYSICS
COLLISIONLESS PLASMA
DISTURBANCES
DRIFT INSTABILITY
EARTH PLANET
ELECTRIC CURRENTS
ELECTROMAGNETIC FIELDS
ELECTRONS
ENERGY SPECTRA
EQUILIBRIUM
MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOTAIL
OXYGEN IONS
PLASMA SHEET
TEARING INSTABILITY