Electrolytic currents in Europa |
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| Authors: | DS Colburn RT Reynolds |
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| Institution: | Space Science Division, NASA-Ames Research Center, Moffett Field, California 94035, USA |
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| Abstract: | Electrical currents should flow in Europa because of its presence in Jupiter's corotating magnetosphere. The possible magnitudes of these currents are calculated assuming that Europa is a differentiated body consisting of an outer H2O layer and a silicate core. Two types of models are considered here: one in which the water is completely frozen and a second in which there is an intermediate liquid layer. For the transverse electric mode (eddy currents), the calculated current density in a liquid layer is approximately 10?5 A m?2. For the transverse magnetic mode (unipolar generator), the calculated current density in the liquid is severely constrained by the ice layer to only 10?10 to 10?11 A m?2, for a total H2O thickness of 100 km, provided that neither layer is less than 4 km thick. The current density is less for a completely frozen H2O layer. If transient cracks were to appear in the ice layer, exposing liquid, the calculated current density could rise to a range of 10?6 to 10?5 A m?2, depending on layer thicknesses, requiring an exposed area of 10?9 to 10?8 of the Europa surface. Electrical heating would be significant only if the ice layer thickness were on the order of 1 m, such as might occur if an exposed liquid surface were to freeze over; the heating under this condition could hinder the thickening of the ice layer. |
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