The solar origins of two high-latitude interplanetary disturbances

Two extremely similar interplanetary forward/reverse shock events, with bidirectional electron streaming, were detected by Ulysses in 1994 [Gosling et al., 1994]. Both events resulted in geomagnetic storms and presumably were associated with coronal mass ejections. In this paper we use the Yohkoh soft X-ray observations to characterize the conditions in the lower corona at the times appropriate for the launching of these two events. We find two strikingly different solar events to be the likeliest candidates: an LDE flare on 20 Feb. 1994, and a extremely large-scale arcade event on 14 April 1994.