XUV and Joule heating driven atmospheric escape from the Early Earth and Earth-sized exoplanets around active stars

Atmospheres of the Early Earth with the Young Sun or close-in exoplanets around K and M dwarfs are subject to large fluxes of solar/stellar radiation from the hosts stars. The solar/stellar radiative flux in the X-ray and extreme ultraviolet ray (XUV) are the key elements for heating the upper atmosphere such as the ionosphere, thermosphere, and mesosphere. First, XUV is absorbed by neutral molecules in the upper atmosphere, excites the molecular quantum states, and consequently heats the upper atmosphere. Second, XUV ionizes neutral molecules and enhances the ionospheric conductivity increasing ion and electron densities together with the increased upper atmospheric temperature. This also leads to the upper atmospheric heating through Joule heating with the ionospheric currents. Here, we present the comparison of XUV and Joule heating in the upper atmospheric heating and hydrodynamic escape rates. In this study, we use a newly developed 3-D upper atmospheric dynamics model, (exo)Planetary Ionosphere and Thermosphere Tool for Research (Planet-ITTR) to calculate XUV heating, ionospheric conductivity, and Joule heating. We simulate the XUV and Joule heating rates and hydrodynamic escape rates in early Earth (Earth-sized exoplanets around active stars) at different distances from the Sun (the host stars). In this presentation, we will also discuss the habitability of the Earth-sized exoplanet around active stars in terms of distance from the host stars.