On the role of dust in the cometary plasma

The cometary coma consists of neutral gas, plasma, and dust grains. Dust grains can influence both the neutral and charged coma's constituents. Usually, presence of dust particles in a plasma results in additional losses of both electrons and ions due to the plasma recombination on the particle surfaces. Solar radiation makes the impact of dust even more complicated, depending on the solar flux, the dust number density, photoelectric properties of the dust particles, the dust particle composition, distribution of sizes, etc. We propose a simple kinetic model evaluating the role of dust particles in the coma plasma chemistry and demonstrate that this role can be crucial resulting in a nontrivial behavior of both the electron and ion densities of the plasma. We show that coma's dust particles can be negatively as well as positively charged depending on their composition. These opposite charges of the grains can result in fast coagulation of dust particles forming complex aggregate shapes of cometary grains.