  Nearly everything we know about extrasolar planets to date comes from optical
astronomy. While exoplanetary aurorae are predicted to be bright at low radio
frequencies (< 1 GHz), we consider the effect of an exoplanet transit on radio
emission from the host star. As radio emission from solar-like stars is
concentrated in active regions, a planet occulting a starspot can cause a
disproportionately deep transit which should be detectable with major radio
arrays currently under development, such as the Square Kilometre Array (SKA).
We calculate the radiometric sensitivity of the SKA stages and components,
finding that SKA2-Mid can expect to detect transits around the very nearest
solar-like stars and many cool dwarfs. The shape of this radiometric light
curve will be affected by scintillation and lensing from the planet's
magnetosphere and thereby encode magnetospheric parameters. Furthermore, these
transits will also probe the distribution of stellar activity across a star's
surface, and will help scrub out contamination from stellar activity on
exoplanet transmission spectra and radial velocity spectra. This radio window
on exoplanets and their host stars is therefore a valuable complement to
existing optical tools.
