The dust halo of Io

The possible formation of dust comas surrounding the volcanic plumes of lo is considered. The main physical ingredient has to do with the electrostatic charging of the tiny solid SO₂ grains from recondensation in the expanding gas plumes. In agreement, with previous estimates by [Johnson et al., 1980; Morfill et al., 1980a], the condensed grains with radii ≤ 0.01 μm are found to be capable of escaping from volcanic plumes under a variety of plasma conditions. Because of the pointing direction of the corotating electric field, the negatively charged grains would be mostly ejected into the Jovian system on the planet-facing side. Under the assumption of electrostatic charging limitation in a dense dusty plasma, the lower limit, of the volcanic ash injection rate can be estimated to be about 37 g s^-1 if the total dust, mass in Loki or Pele is on the order of 10⁸ kg. A much higher mass injection rate (up to 1 kg s^-1) is possible in case the top part of the volcanic plumes has a diffuse structure allowing effective electrostatic charging process. The actual value depends on the local plasma environment, and the structure of the volcanic plumes. It is expected that the observations from the imaging experiment on Galileo will shed important, new light on the existence of the dust halo and hence the identification of the source of the interplanetary dust streams of Jovian origin.