ELECTRICALLY-ACTIVATED CLOUD CHEMISTRY IN THE ATMOSPHERES OF BROWN DWARFS AND EXOPLANETS

The dynamic atmospheres in large, planetary and stellar objects are complex systems, but have a particular fundamental aspect that transcends the fluid description: they are electrical in nature, at least in part.

Just as lightning on Earth is produced by the sudden release of electrical charge accumulated on ice crystals in thunder clouds, active atmospheres containing aerosols and dust particles can develop pockets of intense but transient electrical activity.

Such events have a great significance for atmospheric evolution: the release of free charge into a neutral atmosphere can markedly affect the gaseous chemistry, since this makes possible non-equilibrium chemical pathways that are unavailable via conventional equilibrium processes.

Moreover, the charging of grains and aerosols has an onward impact on the radiation that can be observed remotely. Grain-grain interactions can produce populations of non-thermal free electrons, from processes such as the release of grain charge via localised strong surface electric fields, and from modifying the energy distribution of free electrons moving in the presence of inertial, charged particles.

Anomalous radio signatures have been detected from Brown Dwarf atmospheres, which are an ideal vehicle for exploring the concepts described here.

We propose to explore, theoretically, numerically and with due consideration of observational data, the impact of free and deposited charge on the cloudy atmospheres of Brown Dwarfs, including the generation of such free charge (ionization processes, including lightning) and the characteristic radiation signature of beams, charged aerosols and unique chemistry. In so doing we believe that we can contribute fresh insight into the character and evolution of these fascinating objects.