Japan Geoscience Union Meeting 2014

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Symbol P (Space and Planetary Sciences) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM32_2PM1] Plasma Astrophysics: MHD phenomenon, magnetic reconnection, structure formation

Fri. May 2, 2014 2:15 PM - 4:00 PM 503 (5F)

Convener:*Shuichi Matsukiyo(Department of Earth System Science and Technology, Kyushu University), Shin-ya Nitta(National University Corporation Tsukuba University of Technology), Chair:Ryoji Matsumoto(Graduate School of Science, Chiba University)

2:45 PM - 3:00 PM

[PEM32-16] Minimum spatial scale for maintaining vigorous magnetic reconnection

*Kenya SHIMIZU1, Masaki FUJIMOTO2, Iku SHINOHARA2 (1.University of Tokyo, 2.Institite of Space and Astronautical Science, Japan Aerospace Exploration Agency)

Keywords:magnetic reconnection, electron diffusion region

Magnetic reconnection drives the fast release of magnetic energy in explosive events such as magnetic substorms in the Earth's magnetosphere and flares in the solar corona. On the large scale, reconnection is an MHD-scale process but its rate is controlled by the compact electron diffusion region (EDR), where electrons are not magnetized. Recent kinetic simulations have revealed the structure of EDR in a quasi-steady reconnection rate. In some works, it is suggested that an elongated electron jet in the outflow region does not affect the reconnection rate. However, it is not clear the spatial scale for determining the rate. We find that the minimum spatial scale for maintaining magnetic reconnection by using kinetic simulations on periodic and reflective wall boundary conditions. On the periodic condition, an outflow jet extends a large distance downstream from the X-line with the fast rate of reconnection. However, the influence of periodicity shortens the jet to a narrow structure though the rate of reconnection is still fast. This structure is the minimum spatial scale for maintaining magnetic reconnection. On the other hand, asymmetric reconnection is performed on the reflective wall condition to lead a slow motion of the diffusion region away from the wall, the so called 'X-line retreat.' During the retreat motion an outflow jet is blocked by the wall though the rate of reconnection is maintained. The structure of the blocked jet is very similar to the minimum spatial scale on the periodic condition. We quantitatively show the minimum structure for maintaining magnetic reconnection by comparing the result on these periodic and reflective conditions. We also find the minimum structure is independent of domain sizes but gets smaller with decreasing electron mass.