The application of reconnection theory to astrophysical systems is a relatively recent development in comparison with applications to the terrestrial magnetosphere and the solar corona. The extreme remoteness of objects outside our solar system presents an enormous challenge for plasma physicists, because there are few spatially resolved observations on stellar scales with which to constrain theory. However, advances in Doppler imaging and the development of high-resolution instruments such as the Hubble Space Telescope are beginning to provide some help. Astrophysical magnetism is a huge field which we can only touch upon briefly here, but for an in-depth account the reader is referred to the new monograph by Mestel (1999).

The two astrophysical topics to which reconnection theory has been extensively applied are stellar flares (Mullan, 1986) and accretion disks (Verbunt, 1982). The analysis of stellar flares relies heavily upon the assumption that they are basically similar to solar flares except more energetic (e.g., Gershberg, 1983; Poletto et al., 1988). Flare stars can release 104 to 106 times the amount of energy seen in a large solar flare, but only modest increases in magnetic field strengths and scale-sizes are required to account for this extra amount. The use of reconnection theory in accretion disks has a dual purpose. One is to explain flare-like outbursts generated within disks, and the other is to account for the viscosity needed to allow material in the disks to fall inwards.