Magnetic reconnection as the origin of X-ray jets and Hα surges on the Sun

Abstract

THE solar corona (the outermost portion of the Sun's atmosphere) is far hotter than the 'surface' (the photosphere). Recent observations of X-ray jets^{1á€-4} (collimated flows of plasma at temperatures of a few million degrees) suggest that magnetic reconnectioná€"the cutting of stressed magnetic field lines, which is associated with a violent release of energy, and their subsequent reconnectioná€"may be responsible for heating the corona⁵. But the physical relationship between the X-ray jets, microflares (localized impulsive bursts whose total energy is below the level of the standard flares) and cooler Hα surges⁶ (jets of gas at a temperature of about 10,000 K) has been unclear. In particular, it has been thought⁷ that Ha surges and X-ray jets must arise from independent processes, on the grounds that reconnection would heat any plasma to X-ray-emitting temperatures. Here we present the results of magnetohydrody-namic simulations of the reconnection process, which show that X-ray jets and Ha surges can be ejected simultaneously from microflares^8,9. This suggests that the total energy associated with the microflares is much greater than previously thought, and may be significant in heating the corona.