ULYSSES RADIO AND PLASMA-WAVE OBSERVATIONS AT HIGH SOUTHERN HELIOGRAPHIC LATITUDES

Ulysses spacecraft radio and plasma wave observations indicate that some variations in the intensity and occurrence rate of electric and magnetic wave events are functions of heliographic latitude, distance from the sun, and phase of the solar cycle. At high heliographic latitudes, solar type III radio emissions did not descend to the local plasma frequency, in contrast to the emission frequencies of some bursts observed in the ecliptic, Short-duration bursts of electrostatic and electromagnetic waves were often found in association with de pressions in magnetic field amplitude, known as magnetic holes. Extensive wave activity observed in magnetic clouds may exist because of unusually large electron-ion temperature ratios. The lower number of intense in situ wave events at high latitudes was likely due to the decreased variability of the high-latitude solar wind.