Dust in the arcs of Methone and Anthe

Abstract Methone and Anthe are two tiny moons (with diameter Hedman et al., 2009 ), via the so called impact-ejecta process ( Krivov, Sremcevic, Spahn, Dikarev, Kholshevnikov, 2003 , Spahn, Albers, Horning, Kempf, Krivov, Makuch, Schmidt, Seis, Miodrag, 2006 ). After ejecting and escaping from the moons, these micron-sized particles are subject to several perturbing forces, including gravitational perturbation from Mimas, oblateness of Saturn, Lorentz force, solar radiation pressure, and plasma drag. Particles can be either confined in the arcs due to corotational resonance with Mimas, like their source moons ( Cooper, Murray, Evans, Beurle, Jacobson, Porco, 2008 , El Moutamid, Sicardy, Renner, 2014 , Hedman, Murray, Cooper, Tiscareno, Beurle, Evans, Burns, 2009 , Spitale, Jacobson, Porco, Owen Jr, 2006 ), or pushed outward by plasma drag. Particle sinks are recollisions with the source moon, collisions with other moons, or migration out of the zone of interest. The erosion of particles due to plasma sputtering is also considered ( Johnson et al., 2008 ), although its timescale is much larger than other sinks. Our simulation results show that ejecta from both moons can form maximal number densities between 10 − 4 and 10 − 3 m − 3 . In comparison with the observations of Anthe arc, the peak value in simulations is about an order of magnitude smaller. Plausible explanations for the difference include millimeter-sized particles as additional source and the uncertainties of impactor flux F imp and the yields Y . The longitudinal extension of the Methone/Anthe arc in our simulation is 10.8°/15°, consistent with observations and theory ( Hedman et al., 2009 ). Our results also show the lifetime distributions of particles and the heliotropic behavior of dust introduced by solar radiation pressure ( Hedman et al., 2010a ). The lifetimes of arc particles, defined by the time particles stay in the semi-major axes close to the source moons, are also related to particle size. Smaller ones (