Chromospheres, flares and exoplanets

An interesting and unexpected aspect of stars and planets is whether close-in giant planets are able to noticeably increase chromospheric and coronal emission. Cuntz, Saar & Musielak (2000) presented theoretical evidence that this might indeed be the case. They distinguished between gravitational (tidal) and magnetic interaction, with the latter depending on the stellar and planetary magnetic field strengths and the star-planet distance. Magnetic interaction should manifest itself in increased activity, akin to well-known flaring events between interacting RS CVn binaries, but at much smaller scales. It should also result in an abundance of spots and plagues in the vicinity of the sub-binary point. In the following, we summarize the status of theoretical results and observational verifications.