Conservation of Total Escape from Hydrodynamic Planetary Atmospheres

摘要

Atmosphere escape is one key process controlling the evolution of planets.However, estimating the escape rate in any detail is difficult because thereare many physical processes contributing to the total escape rate. Here we showthat as a result of energy conservation the total escape rate from hydrodynamicplanetary atmospheres where the outflow remains subsonic is nearly constantunder the same stellar XUV photon flux when increasing the escape efficiencyfrom the exobase level, consistent with the energy limited escapeapproximation. Thus the estimate of atmospheric escape in a planet's evolutionhistory can be greatly simplified.