Three‐dimensional propagation of interplanetary disturbances detected with radio scintillation measurements at 327 MHz

Abstract

Interplanetary scintillation (IPS) measurements at 327 MHz have been used to study the three‐dimensional propagation of interplanetary (IP) disturbances between 0.2 AU and near‐Earth distance (∼ 1 AU). IPS data of four events, September 23 and August 24, 1998, and November 4 and 6, 1997, events, in which marked IP disturbances were observed in association with energetic solar flares, have been analyzed in this study. From the analysis of these events it is found that the propagation speed of IP disturbances varies with longitude and latitude. We also found that the fast speed direction does not necessarily agree with the flare normal direction. Slow propagation speeds of IP disturbances appear to be closely associated with the slow speed region of ambient solar wind. This suggests that the large‐scale structure of the solar wind speed may play an important role in determining the propagation speed of IP disturbances, although further study is necessary.