摘要： The importance of Titan's H torus shaped by solar radiation pressure and of hydrogen atoms flowing out of Saturn's atmosphere in forming the broad hydrogen cloud in Saturn's magnetosphere is still debated. Since the Saturnian system also contains a water product torus which originates from the Enceladus plumes, the icy ring particles, and the inner icy satellites, as well as Titan's H2 torus, we have carried out a global investigation of the atomic hydrogen cloud taking into account all sources. We show that the velocity and angle distributions of the hot H ejected from Saturn's atmosphere following electron-impact dissociation of H2 are modified by collisions with the ambient atmospheric H2 and H. This in turn affects the morphology of the escaping hydrogen from Saturn, as does the morphology of the ionospheric electron distribution. Although an exact agreement with the Cassini observations is not obtained, our simulations show that H directly escaping from Titan is the dominant contributor in the outer magnetosphere. Of the total number of H observed by Cassini from 1 to 5RS, ∼5.7×1034, our simulations suggest ∼20% is from dissociation in the Enceladus torus, ∼5–10% is from dissociation of H2 in the atmosphere of the main rings, and ∼50% is from Titan's H torus, implying that ∼20% comes from Saturn atmosphere. •H escaping from Titan is a major source of the H cloud in Saturn's magnetosphere.•Saturn, the ring H2 atmosphere and Enceladus torus are small contributors too.•Titan's H escape rate is 3.8×1027s−1 with a Maxwellian flux distribution at T=150K. 出版者： Elsevier Ltd 出版日期： 2013-09-01 出處： Planetary and space science, 2013-09, Vol.85, p.164-174 資源來源： Elsevier ScienceDirect Journals Complete 版權： 2013 Elsevier Ltd 識別號： ISSN: 0032-0633 識別號： EISSN: 1873-5088 識別號： DOI: 10.1016/j.pss.2013.06.005
