Radiation from Electron Phase Space Holes as a Possible Source of Jovian S-bursts

Radio frequency short burst emissions (25 - 30 MHz), known as Jovian S-bursts, have been observed from the Jovian aurora for over fifty years. These emissions, associated with Io's motion, have a rapidly declining frequency and an extremely narrow bandwidth. While it is widely believed that S-bursts are generated by the electron cyclotron maser mechanism, the mechanism responsible for the rapidly declining frequency and narrow bandwidth is currently uncertain. Similar fine structure has been observed in Auroral Kilometric Radiation (AKR) by several auroral satellites. It was postulated by Mutel et al, [2007] that AKR emissions, created by the electron cyclotron maser, have enhanced growth in ion phase space holes. However, the implied speed (~20,000 km/s) of the structure creating the Jovian S-bursts is significantly faster than that creating the fine structure in AKR emissions (~100s of km/s) indicating that a faster structure is responsible for the fine structure in the radiation observed from Jupiter. We postulate that electron phase space holes radiate in the Jovian Aurora plasma environment and are a possible source of S-burst emission. Electron phase-space holes are ubiquitous in an auroral environment and travel at the implied speeds. This study shows that, under the conditions expected at Jupiter (strongly magnetized), electron phase space holes have enough energy content and can excite electro-magnetic waves. This finding implies that electron phase-space holes may be an important source of radiation from strongly magnetized or from relativistic astrophysical plasmas.