Jupiter radio emission induced by Ganymede and consequences for the radio detection of exoplanets

TL;DR

This study analyzes 26 years of Jupiter radio emissions to identify Ganymede-induced signals, develops a scaling law for plasma interactions, and predicts detectable radio emissions from hot Jupiters with future telescopes.

Contribution

It unambiguously identifies Ganymede-Jupiter radio emissions, establishes a universal radio-magnetic scaling law, and predicts observable radio signals from exoplanets like hot Jupiters.

Findings

Ganymede-induced radio emissions are confirmed and characterized.

A universal scaling law relates radio power to magnetic flux interactions.

Predicted radio emissions from hot Jupiters are detectable with next-generation telescopes.

Abstract

By analysing a database of 26 years of observations of Jupiter with the Nancay Decameter Array, we unambiguously identify the radio emissions caused by the Ganymede-Jupiter interaction. We study the energetics of these emissions via the distributions of their intensities, duration, and power, and compare them to the energetics of the Io-Jupiter radio emissions. This allows us to demonstrate that the average emitted radio power is proportional to the Poynting flux from the rotating Jupiter's magnetosphere intercepted by the obstacle. We then generalize this result to the radio-magnetic scaling law that appears to apply to all plasma interactions between a magnetized flow and an obstacle, magnetized or not. Extrapolating this scaling law to the parameter range corresponding to hot Jupiters, we predict large radio powers emitted by these objects, that should result in detectable radio flux with new-generation radiotelescopes. Comparing the distributions of the durations of Ganymede-Jupiter and Io-Jupiter emission events also suggests that while the latter results from quasi-permanent Alfven wave excitation by Io, the former likely results from sporadic reconnection between magnetic fields Ganymede and Jupiter, controlled by Jupiter's magnetic field geometry and modulated by its rotation.