Science Seminars

3/4/2010 – Planetary Upper Atmospheres under Strong XUV Radiation

Speaker: Feng Tian
Date: Thursday, Mar 04, 2010
Time: 4:00pm
Location: Duane D142

Seminar Abstract:

Solar system terrestrial planets were exposed to strong (10~100 times present levels) soft X-ray and EUV radiation from the young Sun for several hundred million years after their formation. Planetary upper atmospheres expanded to several planetary radii under such XUV radiation and fast escape of major atmosphere gases occurred. The radial outflow, as a result of fast atmosphere escape, caused planetary upper atmospheres to deviate from the traditional hydrostatic equilibrium state, and a new regime, the hydrodynamic regime, is appropriate for the upper atmospheres of early solar system terrestrial planets. Because the hydrodynamic outflow effectively controlled the energy budget in planetary upper atmospheres, the total atmosphere escape could have been conserved regardless which particular atmosphere escape channel could have been dominant. Such a fundamental phenomena also applies to exoplanets such as hot Jupiters (already observed) and hot super Earths (future observations).

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