资源环境科技发展态势分析平台

Imaging of energetic neutral atoms coming from a trans-Europa region and energetic proton observations by Galileo around Jupiter have previously revealed the existence of a neutral gas torus produced by Europa. Energetic sulfur ions observed by Galileo do not show any effect of the Europa torus for Mc Ilwain parameters L > 9.2, surely because ions are multiply charged, so that the torus first needs to bring the ions charge state to one before being able to neutralize them. Signatures of the Europa torus in energetic sulfur ion measurements obtained near the magnetic equator at L = 9.08-9.20 during Galileo orbits C10 and E11 are reported for the first time in this letter. They provide an independent confirmation of the Europa neutral gas torus. Pitch angle distributions suggest that protons might principally interact with a vertically thin neutral oxygen torus, while sulfur ions are lost by charge exchange with a vertically thicker hydrogen torus.