A Study On The Reconnection Rate Of Interplanetary Magnetic Field Reconnection And The Section At The Boundary Of The Outflow Area

As an effective mechanism of magnetic annihilating, magnetic reconnection plays an important role in the interpretation of the outbreak process such as solar flare,magnetospheric substorm, and even the other phenomena in universal. Through magnetic reconnection, the magnetic field topological changes, and the magnetic energy which is stored in the magnetic field will be converted rapidly to kinetic and thermal energy of plasma, accelerating and heating plasma.In recent years, there are a large number of the interplanetary magnetic reconnection exhausts reported successively, which provides a new plasma environment in magnetic reconnection research. No matter what the magnetic reconnection in the theory model and numerical simulation, the exhaust region is a very important structure, especially the magnetohydrodynamic(MHD) discontinuities,which plays a very important role in magnetic energy conversion. We use the Wind spacecraft observation data to make a statistical study on reconnection rate about 87 reported magnetic reconnection exhausts, including 60 exhuasts observed by both ACE and WIND spacecraft. With MHD jump conditions(namely the compatibility relation of Rankine-Hugonio) and multi-spacecraft observations method, we also identify detailedly the discontinuities at the boundaries of the 60 reconnection exhausts. We make a comparative analysis between theoretical models and in situ observations, we found that:(1) the magnetic reconnection rate in the interplanetary solar wind has distribution scope between 0.08% and 25.13%, which is similar in solar flares, and for most of the reconnection exhaust, the reconnection rate is lower than 4.00%;(2) the reconnection exhaust width D and the symmetry of the magnetic field has no obvious effect for reconnection rate; on the other hand, the difference Δβ is a little determining factor; larger reconnection rate events have larger magnetic shear angle,while there is an limit between the reconnection rate and magnetic shear angle:MA=1.327-0.05θ+0.00176θ2;(3) Through MHD jump conditions and multi-spacecraft method, we makeidentification and statistical analysis for the boundary discontinuities of 60 reconnection exhausts which are observed by two-spacecraft in solar wind, and found that most of the discontinuities are tangential discontinuity(TD), a fraction of discontinuities are rotational discontinuities(RD), and only five slow shocks(SSs);The Intermediate shocks(IS) are likely existed in the exhausts boundaries; the boundaries of reconnection exhausts in the interplanetary space can be a pair of TD or RD, and can also be different discontinuities types, a majority of exhausts wedged in TD and RD; however, we didn’t found the exhausts bounded by a pair of SS, which may be formed in initial stage after the reconnection beginning.