Saturn Radii rRs

Figure 4. a) Equilibrium potential (V), and b) Currents (e s 1 cm 2) for a 1 fxm dust particle of material properties <5m=2.4, Em = 400 eV, x=0.1.

3a-c display the results for the equilibrium potential, the charging time, and the dominant currents for our canonical case, 1 /xm dust particle. Here, the equipotential ranges from ~ —2 V at 3.5 Rs, decreasing to ~ —5 V at 6 Rs, and then increasing to ~ —1.5 V at 10 Rs. The charging time for the starred positions is ~ 1 minute. If we perform the same calculations for a 100 times smaller particle with the same material properties, then we find charging times on order of a few hours, which is a signficant fraction of Saturn's rotation period. Also, for a 100 times smaller particle, the secondary electron emission current will be more efficient, causing the smaller particle to charge more positively than for the larger (1 /xm-sized) dust particle.

For an identical dust particle in a geostationary location in Earth's magnetosphere, we calculated dramatic differences in the equipotential values and the charging times when we applied plasma conditions appropriate to 'disturbed' and 'quiet' Earth magnetosphere conditions, and when we slightly varied the material properties from <5m=1.5, Em = 250

Saturn Radii (r/Rs ) Currents

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