THE DISCOVERY OF EXOPLANETS HAS LED TO THE DEVELOPMENT OF SOPHISTICATED MODELS BY NUMEROUS GROUPS FOR THEIR LOWER AND UPPER ATMOSPHERES; HOWEVER MIDDLE ATMOSPHERES HAVE RECEIVED SCANT ATTENTION DESPITE THEIR IMPORTANCE TO ATMOSPHERIC CHEMISTRY ESCAPE AND EVOLUTION AND TO THE INTERPRETATION OF EXOPLANET OBSERVATIONS. AS ON SOLAR SYSTEM PLANETS WE EXPECT THE THERMAL STRUCTURE OF MIDDLE ATMOSPHERES OF EXOPLANETS TO BE DOMINATED BY RADIATIVE BALANCE; HOWEVER RADIATIVE TRANSFER IN THE MIDDLE ATMOSPHERE IS COMPLICATED BY THE BREAKDOWN OF LTE WHICH AFFECTS BOTH THE THERMAL COOLING RATES AND THE THERMALIZATION OF ABSORBED STELLAR RADIATION. MOREOVER THE UPPER LEVELS OF THE MIDDLE ATMOSPHERE ARE INCREASINGLY AFFECTED BY THERMAL CONDUCTION OF ENERGY DOWNWARD FROM THE HOT UPPER ATMOSPHERE. WE PROPOSE TO DEVELOP MODELS FOR THE ENERGY BALANCE IN EXOPLANET MIDDLE ATMOSPHERES THAT PROPERLY INCORPORATE NON-LTE POPULATIONS OF MOLECULAR ENERGY LEVELS. THE CALCULATED TEMPERATURE PROFILES WILL BE CONSTRAINED BY EXOPLANET TRANSIT OBSERVATIONS PARTICULARLY OF THE STRONG ALKALI LINES THAT PROBE THE MIDDLE ATMOSPHERE AND ARE SENSITIVE TO THE TEMPERATURE PROFILE. THE EFFECT OF THE TEMPERATURE PROFILES ON PHOTOCHEMISTRY WHICH OCCURS PRIMARILY IN THE MIDDLE ATMOSPHERE WILL BE INVESTIGATED. THE IMPORTANCE OF THE MIDDLE ATMOSPHERE THERMAL STRUCTURE FOR ATMOSPHERIC ESCAPE THROUGH DISSOCIATION OF H2 AND OTHER MOLECULES IN THE MIDDLE ATMOSPHERE WILL BE DETERMINED AS WELL AS THE IMPACT ON THE PRODUCTION OF HAZES AND HIGH ALTITUDE CLOUDS.

University Of Arizona, Tucson AZ

Investigators