Drivers of atmospheric escape at close-in exoplanets

The upper atmospheres of exoplanets are subject to two important energy sources derived from the host star. First, the stellar photon flux in the EUV and XUV ionizes and heats the upper atmosphere, driving atmospheric heating, affecting the conductance, and enhancing atmospheric escape.Second, the stellar wind's interaction with the planet's intrinsic magnetic field transfers energy to the atmosphere through field aligned currents and Poynting flux. That energy is dissipated in the high latitude cusp and auroral regions through Joule heating which can inflate the atmosphere and also enhance the escape rate. This presentation will discuss recent advances in modeling these energy inputs and their consequences for exoplanetary habitability. In particular, we will discuss atmospheric escape and it's implication for atmospheric evolution including how enhanced EUV and XUV inputs lead to atmospheric loss for close-in exoplanets. We show the scaling of ionized particle escape rates with XUV input and discuss the importance of thermospheric heating and magnetic field interactions. Finally, we discuss new developments required for modeling energy input and effects in the upper atmospheres of exoplanets.