Double current sheet and coronal transients

A double current sheet forms when an opposite magnetic flux emerges into a background magnetic field which has a zero field-line in the corona. It consists of an upper sheet, resulting from the squeezing of field lines near the original zero field region and a lower sheet formed in the region between the new and old fields. We use a pair of linear dipoles to model the background and a pair of line charges to model the emerging field and discuss the formation and evolution of the double current sheet. Matter will condense onto the sheets during their formation. The matter in the lower sheet comes mainly from the transition region and the photosphere; it is further cooled by radiation, giving rise to a low-temperature prominence loop. The matter in the upper sheet comes from the corona and forms a high-temperature coronal loop.This scenario seems to be realized in the coronal transient of 1984 April 14.