Topic/Type: 2.1 MHD, EHD & other fluid methods, Poster

### Very high resolution MHD simulation of magnetic reconnection at high magnetic Reynolds numbers

T. Miyoshi1, K. Kusano2

1 Hiroshima University, Higashi-hiroshima, Japan
2 Nagoya University, Nagoya, Japan

We present a very high resolution resistive magnetohydrodynamic (MHD) simulation of the nonlinear tearing mode for high magnetic Reynolds numbers $\small R_m$. Therefore, a very high resolution numerical scheme is newly developed based on Harten-Lax-van Leer-Discontinuities (HLLD) approximate Riemann solver [Miyoshi and Kusano 2005]. In particular, a two-dimensional Harris current sheet model with a uniform resistivity is adopted as an initial condition in order to achieve as high $\small R_m$ as possible. Thus, high $\small R_m$ MHD reconnection can be successfully simulated.

Simulation results at high $\small R_m$ show that multiple small scale plasmoids are intermittently created by secondary tearing instabilities in a nonlinearly developed thin current sheet and ejected by super-fast-magnetosonic speed, while at not-so-high $\small R_m$ only the primary tearing instability grows steadily. We find that the reconnection rate at high $\small R_m$ is greatly enhanced with the intermittent plasmoid ejections. The results strongly suggest that the nonlinearity in MHD at very high $\small R_m$ could work to make fast magnetic reconnection automatically through the self-destabilization of smaller scale instabilities.