Electron inertial effects on rapid energy redistribution at magnetic X-points

McClements, K.G., Thyagaraja, A., Ben Ayed, N. and Fletcher, L. (2004) Electron inertial effects on rapid energy redistribution at magnetic X-points. Astrophysical Journal, 609(1), pp. 423-438.

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The evolution of nonpotential perturbations to a current-free magnetic X-point configuration is studied, taking into account electron inertial effects as well as resistivity. Electron inertia is shown to have a negligible effect on the evolution of the system whenever the collisionless skin depth is less than the resistive scale length. Non-potential magnetic field energy in this resistive MHD limit initially reaches equipartition with flow energy, in accordance with ideal MHD, and is then dissipated extremely rapidly on an Alfvenic timescale that is essentially independent of Lundquist number. In agreement with resistive MHD results obtained by previous authors, the magnetic field energy and kinetic energy are then observed to decay on a longer timescale and exhibit oscillatory behavior, reflecting the existence of discrete normal modes with finite real frequency. When the collisionless skin depth exceeds the resistive scale length, the system again evolves initially according to ideal MHD. At the end of this ideal phase, the field energy decays typically on an Alfvenic timescale, while the kinetic energy ( which is equally partitioned between ions and electrons in this case) is dissipated on the electron collision timescale. The oscillatory decay in the energy observed in the resistive case is absent, but short-wavelength structures appear in the field and velocity profiles, suggesting the possibility of particle acceleration in oppositely directed current channels. The model provides a possible framework for interpreting observations of energy release and particle acceleration on timescales down to less than a second in the impulsive phase of solar flares.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Fletcher, Professor Lyndsay
Authors: McClements, K.G., Thyagaraja, A., Ben Ayed, N., and Fletcher, L.
Subjects:Q Science > QB Astronomy
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
ISSN (Online):1538-4357

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