简介: |
XUV photons (wavelength between 10--1000nm) are responsible for the heating of the upper atmospheres of solar system planets (Earth, Mars, Venus, Jupiter, Titan, etc.). The young Sun was much more active in its first a few hundred million years (10~100 times present solar) and the early planets were exposed to much stronger XUV radiation. Such XUV radiation environment can also be found in the habitable zon es of active low mass M-stars, which can remain active for much longer time (several billion years) than solar-type stars. Thus studying planetary upper atmospheres under strong XUV radiation is both important for understanding the early evolution history of solar system planets and critical for understanding the habitability of exoplanets. In this talk we will go through different types of planetary upper atmospheres under strong XUV radiation and try to pin down some common characteristics. We will see how fundamental laws of physics, such as the law of energy conservation, manefest themselves in these extreme environments. |
