Statistical ring current of Saturn

摘要

The statistical ring current of Saturn has been determined from the curl of the median magnetic field derived from over 5years of observations of the Cassini magnetometer. The main issue addressed here is the calculation of the statistical ring current of Saturn by directly computing, for the first time, the symmetrical part of the ring current J from the Maxwell equation Δ × B = μ _0J from assembling the perturbation magnetic field B from 2004 through 2010. This study validates previous studies, based on fewer data and not using Δ × B, and shows that the ring current flows eastward (in the + φ or corotation direction) and extends from ～3 R _S to at least ～20 R _S(1 R _S=60,268km), which is the vicinity of the dayside magnetopause; that the ring current has a peak strength of ～75 pA/m ~2 at ～9.5 R _S; and that the ring current has a half-width of ～1.5 R _S. Two outcomes of this study are that the ring current bends northward, as suggested by the "bowl" model of Saturn's plasma sheet, and that the total ring current is 9.2 ± 1.0 MA. In the context of future endeavors, the statistical ring current presented here can be used for calculations of the magnetic field of Saturn for particle drifts, field line mapping, and J × B force.