IPS OBSERVATIONS OF SHORT-TIME SCALE INTERPLANETARY ACTIVITY

We have carried out a program of continuous Interplanetary Scintillati on (IPS) monitoring of the interplanetary activity using Ooty Radio Te lescope (ORT). From May 1990 to March 1991, during the 22(nd) solar ma ximum, a few radio sources were monitored to provide long stretches of IPS data with a high-time resolution of few minutes. These observatio ns covered 0.3 to 0.8 AU region (12 degrees to 70 degrees elongations) around the sun at several heliographic latitudes. During the observat ion, we detected 33 short-time scale IPS events which had significant variation in the scintillation index and solar wind velocity. These we re considered to be due to travelling interplanetary disturbances. A m ulti-component model of plasma density enhancement was developed to es timate the geometry and physical properties of these IPS events. Detai led analysis of 20 of these events suggests, 1. fast IPS events were i nterplanetary signatures of Coronal Mass Ejections (CMEs), 2. the aver age mass and energy of these events was similar to 10(16) gm and 10(33 ) erg respectively, 3. 80% of IPS events were associated with X-ray fl ares on the sun and 50% were associated with geomagnetic activity at e arth. Detailed study of the multicomponent model suggests IPS observat ions at smaller elongations (hence at higher radio frequencies) are mo re suited to detect fast-moving interplanetary disturbances such as pr oduced by CMEs.