抄録
The plasmoid observed in the Earth's magnetotail shows a wide variety of the complicated plasma structures that are not simply described by the standard Petschek reconnection model. The interaction of the plasmoid propagating tailward with the surrounding plasmas of the plasma sheet at rest may be important to understand the plasma sheet structure and the plasma heating observed in the magnetotail. The nonlinear time evolution of the plasmoid is studied by using a large-scale, high-resolution, two dimensional MHD simulation code. Several discontinuities/shocks are formed in association with magnetic reconnection: 1) a pair of the standard Petscheck-type slow shock waves emanating from the X-type neutral point, 2) the tangential discontinuity inside the plasmoid that separates the accelerated plasmas from the original plasma sheet plasmas, 3) the slow shock with a “crab-hand” structure surrounding the front-side of the plasmoid, 4) the intermediate shocks in the edge of the plasma sheet inside the plasmoid, and 5) the contact discontinuity inside the plasma sheet that separates the shock-heated plasmas from the Joule heated plasmas by the magnetic diffusion at the X-type neutral point. We also discuss how those plasma discontinuities/shocks structures are affected by the lobe/mantle plasma condition.
