The search for radio emission from giant exoplanets

Abstract

The intensity of Jupiter's auroral radio emission quickly gave rise to the question whether a comparable coherent emission from the magnetosphere of an extrasolar planet could be detectable. A simple estimation shows that exoplanetary auroral radio emission would have to be at least 1000 times more intense than Jupiter's emission to be detectable with current radio telescopes. Theoretical models suggest that, at least in certain cases, the radio emission of giant exoplanets may indeed reach such an intensity. At the same time, in order to generate such an emission, an exoplanet would need to have a sufficiently strong intrinsic planetary magnetic field. Extrasolar planets are indeed expected to have a magnetic field, but to date, their magnetic field has never been detected. As discussed elsewhere [Grießmeier et al., 2015], the most promising technique to unambiguously observe exoplanetary magnetic fields is to search for the planetary auroral radio emission. The detection of such an emission would thus constitute the first unambiguous detection of an exoplanetary magnetic field. We review recent theoretical studies and discuss their results for the two main parameters, namely the maximum emission frequency and the intensity of the radio emission. The predicted values indicate that detection should be possible using modern low-frequency radio telescopes. We also review past observation attempts, and compare their sensitivity to the predicted emission.

Can we detect aurora in exoplanets orbiting M dwarfs?

“…For a 1-h integration time at 20 to 40 MHz, Grießmeier et al (2011) project a more optimistic sensitivity of about 3 to 30 mJy. The square kilometre array (SKA) will outperform LOFAR in sensitivity, however it is set to operate at frequencies above 50 MHz (Dewdney et al 2009;Griessmeier 2017). For a planet to emit at a frequency of over 50 MHz, it would require a minimum magnetic field strength of ∼ 18G.…”