Abstract:
Coronal mass ejections or CMEs are well known as the drivers of
enhanced interplanetary and geomagnetic activity. They are large expulsions of
material from the Sun, which travel into the interplanetary (IP) medium. and,
if directed towards the earth, can reach the earth in 3-5 days. It is therefore,
necessary to track: a CME from the solar surface through the IP medium till
it reaches the earth. Recent observations from different instruments aboard
SOHO, which simultaneously image the solar atmosphere in different layers
up to a distance of 32 ~, have enabled us to study the initiation and the
propagation of CMEs outward in the heliosphere. These observations reveal
that the halo CMEs are the potential sources of geomagnetic activity at the
earth. However, not all halo CMEsgive rise to the geoeffective IP shocks, which
adds to the problem of space weather forecasting. Here I propose to examine
the characteristics of the geoeffective CMEs observed by LASCO/SOHO and
discuss their role in the prediction of intense geomagnetic storms.
