Three-dimensional propagation of interplanetary disturbances detected withradio scintillation measurements at 327 MHz

Interplanetary scintillation (IPS) measurements at 327 MHz have been used t o study the three-dimensional propagation of interplanetary (IP) disturbanc es between 0.2 AU and near-Earth distance (similar to 1 AU). IFS data of fo ur events, September 23 and August 24, 1998, and November 4 and 6, 1997, ev ents, in which marked IP disturbances were observed in association with ene rgetic solar flares, have been analyzed in this study. From the analysis of these events it, is found that the propagation speed of IP disturbances va ries with longitude and latitude. We also found that the fast speed directi on does not necessarily! agree with the flare normal direction. Slow propag ation speeds of IP disturbances appear to be closely associated with the sl ow speed region of ambient solar wind. This suggests that the large-scale s tructure of the solar wind speed may play an important role in determining the propagation speed of IP disturbances, although further study is necessa ry.