Unified Radio and Plasma Wave Experiment
The Unified Radio and Plasma Wave Experiment (URAP) is a set of instruments on the Ulysses spacecraft. It provides electric field measurements from "DC" to 1 MHz and magnetic field measurements from 0.22 to 450 Hz. These bandwidths permit the study of radio emissions from solar ejecta, interplanetary transients, and planetary magnetospheres and of in situ plasma waves associated with interplanetary shocks, coronal mass ejections, and other transients. The radio observations provide an important remote diagnostic of solar flares and shocks. The plasma wave observations are critical to the understanding of instabilities that exist throughout the interplanetary medium (IPM). Furthermore, analyses of the URAP data permit deriving fundamental characteristics of the solar wind, such as electron density and temperature.
URAP studies have lead to more than 50 published papers on the in-ecliptic, Jovian flyby, and out-of-ecliptic phases of the Ulysses Mission. In the follow-on Ulysses at Solar Maximum Mission, we will have the opportunity to study the Sun and IPM at the peak of the solar cycle, when they are more active. The remote radio observations will serve an important role in distinguishing and separating multiple solar events, which will be observed as superimposed events at the spacecraft. In situ plasma wave activity will also be significantly enhanced due to the increased number of transients. We are looking forward to the comparison of these observations with those of the WIND WAVES experiment, which has been configured similarly to the URAP experiment, and which will provide a 1 AU baseline for the Ulysses out-of-ecliptic observations.