Looking Upstream from the Earth - Interplanetary scintillation measurements of the solar wind using EISCAT

Andy Breen, Richard Falllows, Mario Bisi and Richard Jones
University of Wales, Aberystwyth



The solar wind, by carrying the Sun's magnetic field out into space as it expands, is the agent by which solar disturbances are conveyed to the Earth. It is therefore a key coupling term in solar-terrestrial relations, but much of its evolution as it flows out from the Sun is still imperfectly understood - mainly because of the limited number of instruments capable of providing data at heliocentric distances between the outer corona and the orbit of Venus. Interplanetary scintillation (IPS) measurements, in which the drifting diffraction pattern cast by density irregularities in the solar wind is used as a flow tracer, is one of the few tachniques currently capable of studying these inner regions of the solar wind, and EISCAT is one of the best instruments available for these studies. The talk begins by reviewing some of the advances in understanding of the solar wind that have resulted from EISCAT interplanetary scintillation measurements, before going on to describe some recent results and developments in the technique. It ends with some thoughts on outstanding scientific problems and the part EISCAT IPS can play in resolving them. Phil Williams was one of the co-discoverers of Interplanetary Scintillation and was the first to use EISCAT to make these measurements (in 1981). The current UK IPS programme is very much his creation, so it is most appropriate that EISCAT IPS should form a part of the programme of this meeting.