Poster Abstracts

Name/Affiliation:  Craig Stark (University of St Andrews)

Title:  Coulomb explosion of cloud particles in substellar atmospheres: a source of patchy cloud cover?

Recent observations of Brown Dwarf spectroscopic variability in the infrared infer the presence of patchy cloud cover. The cause of this inhomogeneous coverage could be due to the depletion of cloud particles through Coulomb explosions. The LEAP group focuses on the influence of ionization processes on cloud formation, atmospheric chemistry, meteorology and electromagnetic emission in order to develop an observational diagnostic of atmospheric phenomena such as non-uniform cloud coverage. Ionization processes such as lightning, cosmic ray and Alfvén ionization can produce large-scale volumes of atmospheric plasma in substellar atmospheres. Cloud particles that are immersed in such plasmas become negatively charged and are susceptible to Coulomb explosions, where the electrostatic stress of a body holding a net charge exceeds its mechanical tensile strength, resulting in it breaking up. Our calculations show that charged dust below a critical particle size will be broken up having a significant impact on the distribution of particle sizes as a function of atmospheric pressure. We discuss how such disruption affects the dust cloud particle size distribution, the opacity of the cloud and its ultimate implications for observations.