Ion and electron dynamics generating the Hall current in the exhaust far downstream of the reconnection x-line
- Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1 Ohsawa, Mitaka, Tokyo 181-8588 (Japan)
- Department of Earth and Planetary Science, The University of Tokyo, Bunkyo-ku, Tokyo 114-0015 (Japan)
We have investigated the ion and electron dynamics generating the Hall current in the reconnection exhaust far downstream of the x-line where the exhaust width is much larger than the ion gyro-radius. A large-scale particle-in-cell simulation shows that most ions are accelerated through the Speiser-type motion in the current sheet formed at the center of the exhaust. The transition layers formed at the exhaust boundary are not identified as slow mode shocks. (The layers satisfy mostly the Rankine-Hugoniot conditions for a slow mode shock, but the energy conversion hardly occurs there.) We find that the ion drift velocity is modified around the layer due to a finite Larmor radius effect. As a result, the ions are accumulated in the downstream side of the layer, so that collimated ion jets are generated. The electrons experience two steps of acceleration in the exhaust. The first is a parallel acceleration due to the out-of-plane electric field E{sub y} which has a parallel component in most area of the exhaust. The second is a perpendicular acceleration due to E{sub y} at the center of the current sheet and the motion is converted to the parallel direction. Because of the second acceleration, the electron outflow velocity becomes almost uniform over the exhaust. The difference in the outflow profile between the ions and electrons results in the Hall current in large area of the exhaust. The present study demonstrates the importance of the kinetic treatments for collisionless magnetic reconnection even far downstream from the x-line.
- OSTI ID:
- 22493834
- Journal Information:
- Physics of Plasmas, Vol. 23, Issue 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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