Magnetosphere-ionosphere coupling at Jupiter-like exoplanets with internal plasma sources: implications for detectability of auroral radio emissions

TL;DR

This study models magnetosphere-ionosphere coupling at Jupiter-like exoplanets with internal plasma sources to assess their radio emission detectability, suggesting that rapidly rotating planets around high XUV luminosity stars could be observable at distances over 1 parsec.

Contribution

It provides the first detailed estimation of radio emissions from Jupiter-like exoplanets considering internal plasma sources and stellar XUV effects, informing future detection strategies.

Findings

Detectable radio emissions could originate from planets 1-50 AU away.

High XUV luminosity stars enable detection of planets beyond 50 parsecs.

Rapid rotation enhances the likelihood of observable auroral radio emissions.

Abstract

In this paper we provide the first consideration of magnetosphere-ionosphere coupling at Jupiter-like exoplanets with internal plasma sources such as volcanic moons. We estimate the radio power emitted by such systems under the condition of near-rigid corotation throughout the closed magnetosphere, in order to examine the behaviour of the best candidates for detection with next generation radio telescopes. We thus estimate for different stellar X-ray-UV (XUV) luminosity cases the orbital distances within which the ionospheric Pedersen conductance would be high enough to maintain near-rigid corotation, and we then consider the magnitudes of the large-scale magnetosphere-ionosphere currents flowing within the systems, and the resulting radio powers, at such distances. We also examine the effects of two key system parameters, i.e. the planetary angular velocity and the plasma mass outflow rate from sources internal to the magnetosphere. In all XUV luminosity cases studied, a significant number of parameter combinations within an order of magnitude of the jovian values are capable of producing emissions observable beyond 1 pc, in most cases requiring exoplanets orbiting at distances between ~1 and 50 AU, and for the higher XUV luminosity cases these observable distances can reach beyond ~50 pc for massive, rapidly rotating planets. The implication of these results is that the best candidates for detection of such internally-generated radio emissions are rapidly rotating Jupiter-like exoplanets orbiting stars with high XUV luminosity at orbital distances beyond ~1 AU, and searching for such emissions may offer a new method of detection of more distant-orbiting exoplanets.