SPONTANEOUS CURRENT SHEETS AND STELLAR X-RAY-EMISSION

The x-ray emission from a star like the sun comes from plasma at 10(6) -10(7) K and 10(10) ions cm(-3) trapped in the 100 Gauss bipolar magne tic fields of active regions. The x-ray intensity reaches 10(7) ergs c m(-2) s(-1), which is a measure of the heat input required to maintain the temperature of the emitting gas. The basic energy input is photos pheric convection, which swirls and intermixes the photospheric footpo ints of the bipolar magnetic fields, thereby creating an interlaced to pology of the field lines in the bipolar field above the photosphere. The basic theorem of magnetostatics asserts that almost all field topo logies develop internal tangential discontinuities as the held relaxes to equilibrium. The discontinuities are a necessary and sufficient co ndition for the Maxwell stresses to achieve static balance. It appears that rapid reconnection across these internal current sheets provides the principal heat source for the x-ray corona.