A generalized two-fluid picture of non-driven collisionless reconnection and its relation to whistler waves
A generalized, intuitive two-fluid picture of 2D non-driven collisionless magnetic reconnection is described using results from a full-3D numerical simulation. The relevant two-fluid equations simplify to the condition that the flux associated with canonical circulation Q=m_e ∇ × u_e + q_e B is perfectly frozen into the electron fluid. In the reconnection geometry, flux tubes defined by Q are convected with the central electron current, effectively stretching the tubes and increasing the magnitude of Q exponentially. This, coupled with the fact that Q is a sum of two quantities, explains how the magnetic fields in the reconnection region reconnect and give rise to strong electron acceleration. The Q motion provides an interpretation for other phenomena as well, such as spiked central electron current filaments. The simulated reconnection rate was found to agree with a previous analytical calculation having the same geometry. Energy analysis shows that the magnetic energy is converted and propagated mainly in the form of the Poynting flux, and helicity analysis shows that the canonical helicity ∫P·Q dV as a whole must be considered when analyzing reconnection. A mechanism for whistler wave generation and propagation is also described, with comparisons to recent spacecraft observations.
© 2017 Published by AIP Publishing. Received 17 February 2017; accepted 19 April 2017; published online 5 May 2017. This material is based upon work supported by the National Science Foundation under Award No. 1059519, by the Air Force Office of Scientific Research under Award No. FA9550-11-1-0184, and by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences under Award No. DE-FG02-04ER54755.
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