Origin of the zebra structure in the Jovian decameter radio emission

Abstract

Context. We discuss the origin of quasi-harmonic emission bands that have been observed in the dynamic spectra of the Jovian decameter emission. Aims. We aim to show that the interpretation of the observed structure can be based on the effect of double plasma resonance (DPR) at ion cyclotron harmonics. Methods. According to the proposed model, in the extended source in the upper ionosphere of Jupiter, where the DPR condition is satisfied for one of the ion cyclotron frequency harmonics, the ion cyclotron waves are effectively excited at the frequency of the lower hybrid resonance. The observed electromagnetic radiation with a quasi-harmonic structure arises due to scattering of ion cyclotron waves by supra-thermal electrons. Results. Based on the VIP4 magnetic field model, we determine the longitudes at which the source of the considered radiation can be located. The obtained estimates of the plasma density and its height distribution in the source, as well as the energies of emitting ions and scattering electrons provide information about the plasma parameters in the upper ionosphere of Jupiter. Furthermore, these estimates are in good agreement with the observational data.

Juno Reveals New Insights Into Io‐Related Decameter Radio Emissions

“…The new plasma is then dragged by Jupiter's magnetic field toward corotation, and electrons are accelerated along magnetic field lines toward the planet causing aurorae and DAM emissions. These radio emissions range from 1 to ~40 MHz and have been observed from Earth since 1955 (Burke & Franklin, 1955) and from spacecraft during flybys (Genova & Aubier, 1985). Since DAM is emitted in a narrow conical beam oriented by the magnetic field, the probability of detection depends on the geometrical configuration among the observer, Io, and Jupiter.…”