Abstract
AbstractThe rate of magnetic reconnection is of the utmost importance in a variety of processes because it controls, for example, the rate energy is released in solar flares, the speed of the Dungey convection cycle in Earth’s magnetosphere, and the energy release rate in harmful geomagnetic substorms. It is known from numerical simulations and satellite observations that the rate is approximately 0.1 in normalized units, but despite years of effort, a full theoretical prediction has not been obtained. Here, we present a first-principles theory for the reconnection rate in non-relativistic electron-ion collisionless plasmas, and show that the same prediction explains why Sweet-Parker reconnection is considerably slower. The key consideration of this analysis is the pressure at the reconnection site (i.e., the x-line). We show that the Hall electromagnetic fields in antiparallel reconnection cause an energy void, equivalently a pressure depletion, at the x-line, so the reconnection exhaust opens out, enabling the fast rate of 0.1. If the energy can reach the x-line to replenish the pressure, the exhaust does not open out. In addition to heliospheric applications, these results are expected to impact reconnection studies in planetary magnetospheres, magnetically confined fusion devices, and astrophysical plasmas.
Funder
NASA | Goddard Space Flight Center
National Science Foundation
National Aeronautics and Space Administration
U.S. Department of Energy
Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy
Reference83 articles.
1. Wygant, J. R. et al. Cluster observations of an intense normal component of the electric field at a thin reconnecting current sheet in the tail and its role in shock-like acceleration of the ion fluid into the separatrix region. J. Geophys. Res. 110, A09206 (2005).
2. Drake, J. F., Swisdak, M., Che, H. & Shay, M. A. Electron acceleration from contracting magnetic islands during reconnection. Nature 442, 553–556 (2006).
3. Birn, J. & Hesse, M. Energy release and transfer in guide field reconnection. Phys. Plasmas 17, 012109 (2010).
4. Aunai, N., Belmont, G. & Smets, R. Proton acceleration in antiparallel collisionless magnetic reconnection: kinetic mechanisms behind the fluid dynamics. J. Geophys. Res. 116, A09232 (2011).
5. Egedal, J., Daughton, W. & Le, A. Large-scale electron acceleration by parallel electric fields during magnetic reconnection. Nat. Phys. 8, 321 (2012).
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