The space weather environment of exoplanets is directly determined by their host stars. Stellar rotation rates and magnetic fields drive outflows that fill planetary systems with a supersonic wind of magnetised plasma.
Solar-type stars form with a wide range of rotation rates, but wind angular momentum loss (and internal redistribution) leads to the onset of the so-called Skumanich relation, which links age and rotation rate after about 650 Myr. Using large-scale magnetohydrodynamic simulations constrained by tomographic observations of Zeeman splitting in the stellar photosphere, we can explore how realistic, multipolar, and often misaligned stellar magnetic fields shape space weather properties.
Extending the wind simulations to include the interaction between stellar wind and planetary magnetospheres permits us to quantify the external space weather conditions in which exoplanets are suffused, and the balance between wind pressure, planetary magnetic shielding, and atmospheric erosion. The latter is strongest for young, active stars, where dense, fast winds and frequent eruptive events can erode atmospheres and induce strong magnetospheric currents. We present a promising link between wind models and observational signatures from exoplanetary systems, showing how star-planet interaction may produce detectable radio signals that trace the surrounding plasma environment.
At PHAB, I aim to build on previous work by connecting stellar-wind modelling with models of energetic particle transport and the upper atmospheric layers of exoplanets to better understand how these factors govern atmospheric escape and long-term habitability.