The vast majority of detected exoplanets are orbiting cool stars. Moreover, most rocky exoplanets detected in the “habitable zone” are in close-in orbits around very low-mass stars. Low-mass stars are typically very active and these close-in planets will be exposed to much stronger magnetic effects than those we experience on Earth. It is now recognized that energetic stellar photon and particle radiation evaporates and erodes planetary atmospheres and controls upper atmospheric chemistry.
Using a realistic 3D non-ideal MHD model, that has been validated for the Sun, we have simulated the space weather conditions of a number of exoplanetary systems. In this talk I will discuss how their conditions depend on the magnetic activity of the star and the orbital distance of the planet.
The secular evolution of magnetic activity is also key to understanding the space weather of exoplanets. In that context, I will discuss how magnetic activity scales with rotation and, therefore, with age, and the resulting integrated energetic particle and photon irradiation doses and its effects on exoplanetary environments.