Ground and space-based studies of solar wind acceleration

Observations of interplanetary scintillation (IFS) made with the EISCAT and VLBA systems show that the fast high-latitude solar wind accelerates very rapidly, reaching its "coasting" velocity inside 10 solar radii (R) from the Sun. These observations place significant models seeking to explain the the solar wind. A model proposed recently by McKenzie et al. can reproduce this rapid acceleration providing that ion temperatures in the corona increase very rapidly with height, reaching a maximum of similar to 10(7) K at 2 R. IPS observations of the slow solar wind suggest that acceleration may be considerably slower than in the fast wind, continuing out about 30 R. This is consistent with observations from LASCO. In this paper we present IFS results to date and describe a co-ordinated programme of observations involving EISCAT and instruments aboard SOHO.