CMEs are large-scale magnetized plasma structures carrying billions of tons of material that erupt from a star and propagate in the stellar heliosphere, interacting in multiple ways with the stellar wind. Due to the high speed, intrinsic magnetic field and the increased plasma density compared to the stellar wind background, CMEs can produce strong effects on planetary environments when they collide with a planet. The main planetary impact factors of CMEs, are associated interplanetary shocks, energetic particles accelerated in the shock regions, and the magnetic field disturbances. All these factors should be taken into account during the study of evolutionary processes on exoplanets and their atmospheric and plasma environments. CME activity of a star may vary depending on stellar age, stellar spectral type and the orbital distance of a planet. Because of relatively short range of propagation of majority of CMEs, they impact most strongly the magnetospheres and atmospheres of close orbit (< 0.1 AU) exoplanets.

We describe our method for measuring mass loss rates of F–M main sequence stars with high-resolution Lyman-α line profiles. Our diagnostic is the extra absorption on the blue side the interstellar hydrogen absorption produced by neutral hydrogen gas in the hydrogen walls of stars. For stars with low X-ray fluxes, the correlation of observed mass loss rate with X-ray surface flux and age predicts the solar wind mass flux between 700 Myr and the present.