COMETS AS PROBES OF THE INTERPLANETARY MEDIUM

Comets are natural probes of the interplanetary medium spanning it thr ee dimensionally at all inclinations to the ecliptic plane and the ext ent of coverage stretching well beyond the orbits of the planets. They , are also the main contributors to interplanetary dust. The ion tail structures in comets are sensitive indicators of the state of interpla netary magnetic field and solar wind structure in the region. The impo rtance of ion tail transient events in comets, which can be monitored by dedicated small telescopes, is brought out and their relation to th e sector boundary crossings of the interplanetary magnetic field discu ssed.