ULYSSES SPACECRAFT OBSERVATIONS OF RADIO AND PLASMA-WAVES - 1991-1995

The radio and plasma wave investigation of the Ulysses spacecraft miss ion provided nearly continuous observations of wave electric fields (l ess than 1 MHz) and magnetic fields (less than 450 Hz) from spacecraft launch in late 1990 through perihelion in 1995 and beyond. The Ulysse s spacecraft reached heliographic latitudes of +/-80 degrees, providin g a unique opportunity to study wave activity in fast solar wind emana ting from polar coronal holes and to examine the differences relative to waves in the streamer belt. These data led to the discovery that ma ny magnetic held depressions (magnetic holes) are populated by waves a t the electron plasma frequency; such phenomena occur much more freque ntly in high-latitude, fast solar wind. At high latitudes, Ulysses fre quently detected the waves conventionary assumed to be ion-acoustic wa ves; however, the electron-proton temperature ratio at these latitudes is always less than one, suggesting that the waves must be some other mode. Electrostatic and electromagnetic waves at lower frequencies al so evidenced marked changes as Ulysses recurrently entered and exited the streamer belt during the ''fast latitude scan'' phase of its orbit . These variations with heliographic latitude, as well as variations w ith distance from the Sun, are presented and interpreted.