Emission processes are both probing tools and phenomena of critical importance for the understanding of the physico-chemistry, the dynamics, the evolution, and the thermal equilibrium of planetary upper atmospheres and mesospheres. Depending on the nature of the emissions several outstanding directions can be highlighted.

Particle precipitation, such as electrons in aurora or photoexcitation (dissociative/ionizing), are at the origin of several fluorescence processes. Direct excitation, secondary excitation, and even chemical processes or transport of atoms lead to several kinds of emission. Recombination processes are important in mesospheres.

Planetary mesospheres are also impacted by energetic processes occurring within the deep atmosphere, such as lightnings which induce optical emissions as sprites and Elves. Although being transient and short, these phenomena share basic physics with other kinds of airglow.

On top of these non-thermal emissions, thermal interactions occur, leading to a global view of the energetic budget of atmospheres. To account for these processes, several kinds of instruments in the IR, UV or visible range are used, along with different types of models (kinetic transport, radiative transfer, chemical), supported by recent developments in spectroscopy and chemistry.

This session focuses on recent results and especially on the comparison between models and observations of various types of airglow and aurorae. We invite presentations on the atmospheres of Mars, Venus, Titan, Jupiter, Saturn, Mercury, comets and Earth. Earth and cometary contributions are particularly welcome in this comparative planetology session as they will foster discussions between communities. Recent results from planetary missions such as Mars Express, Venus Express, Akatsuki, and Cassini (not an exhaustive list) will be presented. Laboratory and joint developments between theoreticians and experimentalists will also be addressed, as a critical step towards a better understanding of airglow/aurorae phenomena at Earth and the other planets. Papers focusing on new and upcoming instrumental developments aimed at a better understanding of airglow processes are also encouraged.

The Poster and Summary Discussion session PSD18 is subsequently organised as a forum where discussions about specific topics for the planetary aeronomy community are welcome, e.g., on recombination processes and their impact on the auroral physics and fluorescence mechanisms, polarisation of emission lines, and processes at lower altitudes (mesosphere) for which a joint half-session with NH1.4/AS4.4 "Lightning: physics, detection and atmospheric effects" is organized in an effort to stimulate exchanges between communities working on all planetary objects.


Confirmed solicited people: J.M.C. Plane (University of Leeds, UK), J.-C. Gérard (University of Liège, Belgium), G. Fischer (Space Research Institute, Graz, Austria)