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

摘要

In this paper we provide the first consideration of magnetosphere-ionospherecoupling at Jupiter-like exoplanets with internal plasma sources such asvolcanic moons. We estimate the radio power emitted by such systems under thecondition of near-rigid corotation throughout the closed magnetosphere, inorder to examine the behaviour of the best candidates for detection with nextgeneration radio telescopes. We thus estimate for different stellar X-ray-UV(XUV) luminosity cases the orbital distances within which the ionosphericPedersen conductance would be high enough to maintain near-rigid corotation,and we then consider the magnitudes of the large-scale magnetosphere-ionospherecurrents flowing within the systems, and the resulting radio powers, at suchdistances. We also examine the effects of two key system parameters, i.e. theplanetary angular velocity and the plasma mass outflow rate from sourcesinternal to the magnetosphere. In all XUV luminosity cases studied, asignificant number of parameter combinations within an order of magnitude ofthe jovian values are capable of producing emissions observable beyond 1 pc, inmost cases requiring exoplanets orbiting at distances between ~1 and 50 AU, andfor the higher XUV luminosity cases these observable distances can reach beyond~50 pc for massive, rapidly rotating planets. The implication of these resultsis that the best candidates for detection of such internally-generated radioemissions are rapidly rotating Jupiter-like exoplanets orbiting stars with highXUV luminosity at orbital distances beyond ~1 AU, and searching for suchemissions may offer a new method of detection of more distant-orbitingexoplanets.