The flux-nuclear mechanism as the cause of cometary outbursts – a solution to an old problem

ABSTRACT The paper presents a new flux-nuclear mechanism based on which cometary outbursts can be explained. This mechanism should be considered as a two-step process. In the first stage, it is necessary to consider the sublimation flux that occurs through the porous structure of the cometary nucleus. The second stage is the reaction of the cometary nucleus to the sublimation that is taking place. The consequence of this process is responsible for the migration (redistribution) of porous agglomerates on the surface of the cometary nucleus, the formation of landslides (local avalanches), the formation of dunes, the emission of porous agglomerates into the coma, and the loosening of the surface layer, which is consequently destroyed. These processes are part of the broadly understood cometary activity, i.e. the interaction of sublimating ice with the cometary nucleus. As a result of intense ice sublimation, the loose cometary material is ejected into the coma, which causes an increase in the total scattering cross-section. Then the incident sunlight scatters more effectively, which leads to a rise in the cometary brightness, i.e. its outburst. Based on the flux-nuclear mechanism and calculations performed for a model comet from the Jupiter family, it was determined that the upper limit of the outburst is equal to 4 mag. This means that the obtained value of the outburst amplitude fits the typical range of change in the cometary brightness.