T. Matsuyama

Fast compression of a current sheet during externally driven magnetic reconnection

Magnetic reconnection of two toroidal plasmas with arbitrary q values revealed a dependence of sheet-current dissipation and ion heating on ion-gyromotion. Effective sheet-current resistivity was found to increase significantly, when an external force compressed the current sheet shorter than the ion-gyroradius, and both the reconnection speed and ion temperature increased with decreasing current sheet width and with increasing ion-gyroradius.

New relaxation of merging spheromaks to a field reversed configuration

A novel high β relaxation to a field reversed configuration (FRC) has been investigated by axially colliding two spheromaks with opposing toroidal magnetic fields. The β value of the merging toroids increases from 0.1 to 0.7-1.0 within 15 μs, indicating an equilibrium transition from the low β spheromak to the high β FRC. An important finding is that the merging spheromaks relax either to a high β FRC or to another low β spheromak, depending on whether the initial normalized magnetic helicity given to these spheromaks is smaller or larger than a threshold value. This fact suggests that the FRCs are equipped with some global stability as robust as the Taylor magnetic energy minimum state.

Fast magnetic reconnection with anomalous ion heating and its application

Abstract Magnetic reconnection of two toroidal plasmas with the third field component Bx parallel to the X-lines revealed a clear dependence of sheet-current resistivity and ion heating energy on the sheet-width normalized by the ion gyroradius. Initially, the effective resistivity of sheet-current stayed constant, but it increased significantly when the sheet was compressed shorter than the ion-gyroradius. The anomalous current-sheet dissipation was followed by large increase in ion outflow velocity and ion temperature. This anomalous effect caused both the reconnection speed and the ion heating energy to increase with external compression force and inversely with the Bx component. These properties of reconnection lead us to a new controlled plasma heating for various fusion plasmas and other industrial plasmas.