INTERPLANETARY SCINTILLATION OBSERVATIONS OF THE HIGH-LATITUDE SOLAR-WIND

Until the ULYSSES spacecraft reached the polar regions of the solar wi nd, the only high-latitude measurements available were from indirect t echniques. The most productive observations in regions of the solar wi nd between 5 R. and 200 R. have been the family of radio scattering te chniques loosely referred to as Interplanetary Scintillation (IPS) (Co les, 1978). Useful observations can be obtained using a variety of rad io sources, for example spacecraft beacons, planetary radar echoes and compact cosmic sources (quasars, active galactic nuclei, pulsars, gal actic masers, etc.). However for measurement of the high-latitude sola r wind cosmic sources provide the widest coverage and this review will be confined to such observations. IPS observations played a very impo rtant role in establishing that polar coronal holes (first observed in soft x-ray emission) were sources of fast solar wind streams which oc casionally extend down to the equatorial region and are observed by sp acecraft. Here I will review the IPS technique and show the variation of both the velocity and the turbulence level with latitude over the l ast solar cycle. I will also outline recent work and discuss compariso ns that we hope to make between IPS and ULYSSES observations.