Astrophysics Colloquium - Radio observations of extrasolar space weather

Low-frequency radio observations (< a few hundred MHz) uniquely probe several processes that shape space weather around exoplanets, including coronal mass ejections and energetic particle events. They also provide the only known means of measuring the magnetic fields of planets and cold brown dwarfs. Such observations are routine in the solar system, and the extrasolar frontier is now coming within reach thanks to powerful new radio telescopes such as LOFAR, uGMRT, and MeerKAT. I will describe an observational program designed to systematically survey the low-frequency radio sky for emission from stars, brown dwarfs, and exoplanets with unprecedented sensitivity. I will present early successes from this effort, including (a) evidence for magnetic interaction between a star and its planet, (b) a measurement of the magnetic field of a cold brown dwarf, and (c) the detection of coronal mass ejections and energetic particle events from nearby stars. I will conclude with an outlook on how radio astronomy’s unique diagnostic capabilities can advance our understanding of stars brown dwarfs and exoplanets over the coming decade.