Extremely long-baseline interplanetary scintillation measurements - a tool for probing solar wind structure

Breen, A.1, Fallows, R.1, Dorrian, G.1 and Bisi, M.2

1 University of Wales, Aberystwyth, Ceredigion, UK
2 University of California, San Diego, California, USA

Two-site measurements of interplanetary scintillation have been used to study solar wind velocities for over 30 years, but recent developments using EISCAT and MERLIN have led to new insights into the large-scale structure of the inner heliosphere. In this presentation we discuss these observations and present highlights from recent results. These include evidence of a distinct change in fast solar wind speed between the polar crown outflow and the flow from the equatorwards extension of a polar coronal hole, observations of super-radial expansion of tte fast wind at heliocentric distances of 25-80 solar radii and evidence for flow rotation in stream interaction regions and in the solar wind perturbed by the passage of a iCME. We compare our results with those obtained from tomographic reconstructions based on lower-frequency IPS observations from the STELab telescoep network in Japan and show that the combination of the two IPS approaches provides a powerful tool for studying solar wind structure.