MAGNETIC RECONNECTION AS THE ORIGIN OF X-RAY JETS AND H-ALPHA SURGES ON THE SUN

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(1-4) (collimated flows of plasma at temperatures of a few million degrees) suggest that magnetic reconnection-the cutting of stressed magnetic field lines, which is associated with a violent release of energy, and their subsequent reconnection-may be responsible for heating the corona(5). 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 H alpha surges(6) (jets of gas at a temperature of about 10,000 K) has been unclear, In particular, it has been thought(7) that H alpha 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 magnetohydrodynamic simulations of the reconnection process, which show that X-ray jets and H alpha 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.