Stellar Magnetic Fields and Radio Emissions from Star–Planet Systems

Low-frequency radio emissions from star–planet systems provide a direct probe of planetary magnetic fields and plasma interactions in extrasolar environments. With the advent of large radio facilities and wide-field surveys, ensemble predictions of radio emission properties have become essential for statistically interpreting the first detections. They can also help selecting promising targets. We present a major update of the PALANTIR (Prediction Algorithm for star–pLANeT Interactions in Radio) predictive framework for radio emissions from star–planet interactions and planetary magnetospheres, based on the scaling law that relates the emitted radio power to the Poynting flux of the stellar wind intercepted by a planetary obstacle. A key input of the model is the stellar large-scale magnetic field, for which we have built a database of available measurements plus an extrapolation method for unmeasured values. Using this approach, we compute stellar wind properties, planetary obstacle sizes, and electron cyclotron maser emission conditions to predict maximum emission frequencies and flux densities both for exoplanetary magnetospheric emissions and for exoplanet–induced stellar emissions, for a large number of star–planet systems. While individual system predictions are subject to large uncertainties, the framework provides statistically meaningful ensemble trends and identifies likely promising targets for current and future low-frequency radio facilities.