Dynamics of auroral arcs during double breakups

Characteristic features of double breakups and auroral-arc dynamics have be en studied for different versions of auroral substorm dynamics before and a fter the contact of breakups. It has been shown that the are velocities var y in different ways depending on the scenario of substorm development after contact. Double breakups may be associated with the appearance of two neut ral lines in the magnetospheric tail. In the framework of the spontaneous r econnection, differences in the auroral dynamics before and after the conta ct of double breakups can be determined by the peculiarities in the magneti c field, i.e., by whether the most remote field line is located on closed o r open field lines.