Research Interests
Comparative Planetary Upper Atmospheres.

The comparative approach to planetary problems is becoming increasingly fruitful as new information from various planet atmospheres is assimilated. The long-term objective in my program of research is to contrast and compare the processes responsible for the structure and dynamics of the Venus, Earth, Mars and Jovian planet upper atmospheres. This is important to our overall understanding of how atmospheres are driven and how they change over time, both naturally and in the case of Earth as a result of human influence.

My study of upper atmospheres specifically involves a systematic examination of their neutral/ion chemistry, radiation, airglow, and dynamics above ~50 km. This strategy includes modeling their mesospheric, thermospheric, and ionospheric responses to different forcings using the 3-D thermospheric general circulation model (TGCM) utility at the National Center for Atmospheric Research (NCAR). In addition, the Michigan Global Ionosphere Thermosphere Model (GITM) has recently been adapted to the atmospheres of Mars and Jupiter. Both the TGCM and GITM codes couple chemical, radiative, and dynamical processes self-consistently; this feedback is critical to understanding upper atmosphere responses to changing external forcings (e.g. solar, magnetospheric, tidal, gravity wave).

Data from various terrestrial and planetary spacecraft missions and ground-based observations is being used to validate these models and compare the relevant atmospheric processes. Recently, aerobraking data from three Mars orbiters (Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter) was used to constrain Mars TGCM simulations, from which the underlying dynamical processes linking the Mars lower and upper atmospheres were investigated. More recently, a ground to exobase Mars GITM code has been developed and validated for use in data analysis activities associated with the upcoming MAVEN mission to Mars. The solar wind interaction with the Mars upper atmosphere (i.e. thermosphere, ionosphere, exosphere variations) is the focus of our modeling activities. A web site is available that presents an archive of Venus, Earth, and Mars upper atmosphere TGCM simulations.