This project will investigate the hypothesis that dust clouds are a major source of charge separation and discharge processes in very low mass, extrasolar objects like M-dwarfs, Brown-Dwarfs, and planets. The aim is to model charging, dust formation and sedimentation in dusty media to understand how the atmospheric ionisation mechanisms change at the border from stars to planets in the M-dwarf--Brown-Dwarf transition region where radio emission starst to exceed X-ray emission, and to investigate the physics and the occurrence of intra-cloud lightning outside our solar system. Lightning is suggested to have triggered the occurrence of life on Earth.
Dusty media are generally very common on Earth and in space, for example in volcano plumes that influence the local climate on Earth, on Mars where it blocks Mars-Rover's wheels, in dust-clouds in Brown Dwarfs and planets which determine their chemistry and their detectability, or in planet-forming disks. All have in common that dust of mixed composition is abundant in a turbulent environment in a variety of sizes. This project will perform a characterisation of dusty astrophysical plasma, systemically study charge separation processes and draw comparison to known scenarios in volcanos and Martian plasmas. The project determines stellar parameter and dust cloud characteristics (e.g. cloud height) for which dust cloud charging becomes important, and under which conditions lightning can occur. A charge conservation model will be coupled to a non-equilibrium chemistry to search for discharge-related molecules and for pre-biotic molecules that might occur during lightning. Applications to standard model atmospheres will be carried out to study the influence on the spectral energy distribution and the object's albedo. The long-term aim of this project is to solve the dust and charge conservation equations together with the magnetic field equations in order to study the development of radio emission in low-mass objects.
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