Statistical study of the Jovian decametric radio emissions based on multiple-view observations from remote radio instruments

Abstract

To better understand the physical processes associated with Jovian decametric (DAM) radio emissions, we present a statistical study of DAM emissions and inferred characteristics of DAM sources based on multiview observations from the Wind and STEREO spacecraft. Altogether, we analyze 81 isolated, strong events in radio dynamic spectra from 2008 to 2014. The apparent rotation speed of DAM events derived from multiple spacecraft observations can be used to distinguish Io-related and non-Io-related DAM emission. We find that the rotation speed of Io-DAM events is in the range of 0.15–0.6 ΩJ and that the rotation speed of non-Io DAM events is between 0.7–1.2 ΩJ. We find the occurrence probability of isolated, strong Io-DAM events to be about seven times that of isolated, strong non-Io DAM events. We locate the sources of 79 DAM events (including ten events observed by the Nançay Decameter Array) and infer their emission angles and associated electron energy. Our statistical results show that the DAM source locations (both Io and non-Io) are distributed in three preferred high-latitude regions, with two in the southern hemisphere (around 30° to 150° and around 270° to 330° in System III longitudes) and one in the northern hemisphere (around 150° to 210°), which is probably caused by the nonsymmetrical topology of Jupiter’s magnetic field. The difference between the Io-DAM source footprints and the Io auroral UV spots changes with the Io position in System III longitude, which is consistent with previous results. In addition, for the same type of DAM events (e.g., type A or C), the emission angles of non-Io DAM events are smaller than those of Io-DAM events, and all the emission angles range from 60° to 85°. Correspondingly, the energy associated with the electrons responsible for exciting the radio emissions is estimated to range between 2 and 22 keV.