Magnetic reconnection ahead of a coronal mass ejection

Abstract

On 29 November 1990 the Ulysses spacecraft passed through a series of interplanetary structures which suggest that reconnection had occurred on open field lines ahead of a coronal mass ejection (CME), changing the magnetic topology of the upstream region. We observe in sequence 1) a heat flux dropout, 2) a region of counterstreaming halo electrons which does not appear to be a CME, and 3) a region of counterstreaming halo electrons which is a CME. We suggest an interpretation in which upstream of the CME Ulysses passed first through a region magnetically disconnected from the Sun and then through a region magnetically connected back to the solar corona at both ends, both of which were created by reconnection of open field lines ahead of the CME. Such reconnection provides a method for producing a heat flux dropout / counterstreaming suprathermal electron pair of signatures in interplanetary space that has not been previously described.