X-Ray Flares and Outflows Driven by Magnetic Interaction Between a Protostar and its Surrounding Disk

Abstract

Here we present a model of hard X-ray flares and hot plasma outflows (optical jets) observed in protostars. Assuming that the dipole magnetic field of a protostar threads the protostellar disk, we carried out 2.5-dimensional magnetohydrodynamic (MHD) simulations of the diskstar interaction. The closed magnetic loops connecting the central star and the disk are twisted by the rotation of the disk. In the presence of resistivity, magnetic reconnection takes place in the current sheet formed inside the expanding loops. Hot, outgoing plasmoid and post flare loops are formed as a result of the reconnection. Numerical results are consistent with the observed plasma temperature (10 7 – 10 8 K), the length of the flaring loop (10 11 – 10 12 cm), and the speed of optical jets (200 – 400 km s −1 ).