2010ApJ...721.1034M

Magnetic reconnection events in the atmospheres of low-mass dwarf stars can be classified as either slow or fast, depending on whether ohmic diffusion or Hall currents dominate in the reconnection process. We suggest that the separation of reconnection into slow and fast categories can help to explain some systematics of low-mass dwarfs as regards their emissions in X-rays, Hα, and radio. On the one hand, in the warmer dwarfs (<M7), where electrical resistivities are small, fast reconnection is permitted, and this can explain the occurrence of flares and "quiescent" coronal heating. On the other hand, the fact that the coolest dwarfs (>M7) are inefficient emitters in Hα and X-rays but strong emitters in radio, may be understood in the context that only slow reconnection is permitted to occur in those stars, as a result of high electrical resistivity. However, even though only slow reconnection is permitted in the latter stars, the speed of the outflow jets from reconnection sites can serve as efficient sources of radio emission as a result of the electron cyclotron maser instability.