Magnetic Reynolds Number Dependence of Reconnection Rate and Flow Structure of the Self‐Similar Evolution Model of Fast Magnetic Reconnection

This paper investigates Magnetic Reynolds number dependence of the``self-similar evolution model'' (Nitta et al. 2001) of fast magneticreconnection. I focused my attention on the flow structure inside and aroundthe reconnection outflow, which is essential to determine the entirereconnection system (Nitta et al. 2002). The outflow is consist of severalregions divided by discontinuities, e.g., shocks, and it can be treated by ashock-tube approximation (Nitta 2004). By solving the junction conditions(e.g., Rankine-Hugoniot condition), the structure of the reconnection outflowis obtained. Magnetic reconnection in most astrophysical problems ischaracterized by a huge dynamic range of its expansion ($sim 10^7$ for typicalsolar flares) in a free space which is free from any influence of externalcircumstances. Such evolution results in a spontaneous self-similar expansionwhich is controlled by two intrinsic parameters: the plasma-$beta$ and themagnetic Reynolds number. The plasma-$beta$ dependence had been investigated inour previous paper. This paper newly clarifies the relation between thereconnection rate and the inflow structure just outside the Petschek-like slowshock: As the magnetic Reynolds number increases, strongly converging inflowtoward the Petschek-like slow shock forms, and it significantly reduces thereconnection rate.Comment: 16 pages. to appear in ApJ (2006 Jan. 20 issue