Magnetic Reconnection as the Origin of Galactic-Ridge X-Ray Emission

Abstract

We present a scenario for the origin of the hot plasma in our Galaxy as a model of strong X-ray emission [∼ 3 – 10 keV; LX(2 – 10 keV) ∼ 1038 erg s−1], called Galactic Ridge X-ray Emission (GRXE), which has been observed near to the galactic plane. GRXE is thermal emission from a hot component (∼ 7 keV) and a cool component (∼ 0.8 keV). Observations suggest that the hot component is diffuse, and that it is not escaping away freely. Both what heats the hot component and what confines it in the galactic ridge still remain puzzling, while the cool component is believed to be created by supernovae. We propose a new scenario: the hot component is heated by magnetic reconnection, and confined by a helical magnetic field produced by magnetic reconnection. We solved two-dimensional magnetohydrodynamic equations numerically to study how magnetic reconnection, triggered by a supernova explosion, creates hot plasmas and magnetic islands (helical tubes), and how the magnetic islands confine the hot plasmas in the Galaxy. This is one of the possible mechanisms to trigger reconnection in the Galaxy. We conclude that magnetic reconnection is able to heat the GRXE plasma if the magnetic field is localized in an intense flux tube with Blocal ∼ 30 μG.