FORMATION OF CURRENT SHEETS BY PHOTOSPHERIC COMPRESSION

This paper examines a mechanism proposed by Low (1987) for the formati on of current sheets in two-dimensional potential magnetic fields in t he solar corona, by photospheric compression parallel to the plane of the field. In contrast to earlier work by Syrovatskii (1974) this mech anism does not require a magnetic neutral point. We develop methods fo r analysing the change in B due to a compression, and for detecting cu rrent sheets by counting the rotations of the magnetic field vector al ong the photosphere. Methods are also given for calculating the positi on and lengths of the current sheets, and the magnetic energy they rel ease on reconnection. For the more realistic field which decays suitab ly at infinity, we find that only nonlinear compressions of restricted form can generate current sheets, and that the energy released is sma ll. Unless other example fields or compressions yield much larger ener gies, this mechanism seems an unlikely explanation for solar flares.