On the possibility of coherent cyclotron emission from extrasolar planets

Abstract

A model of the coherent cyclotron emission from extrasolar planets is presented. Scaling laws known to operate in our solar system (including scaling laws of planetary magnetic fields and the radiometric Bode's law of radio power generation) are applied to the extrasolar systems. We consider the possibility that each of the extrasolar planets possesses a substantial planetary magnetic field which is in quasi-continuous interaction with the local stellar wind. Cyclotron emission from extrasolar planets is then driven by the stellar wind/magnetospheric interaction, much like the coherent cyclotron radio emission processes associated with planets in our solar system. Based on the model results, the best candidate for solar-wind-driven cyclotron emission is Tau Bootes, with an expected median amplitude of about 2 janskys (1 Jy = 10-26 W m-2 Hz-1) at 28 MHz, an intensity level of about a factor of 100 below the current limit of detectability. However, variations in the local stellar medium could conceivably increase power levels by a factor of 100 for short periods of time. Like the solar planets, the extrasolar planets should radiate episodically, with emission reoccurring at the planetary rotation period. Thus spectral integration techniques could also be applied to improve the likelihood of detectability. Copyright 1999 by the American Geophysical Union.