The Jovian hydrogen bulge: Evidence for co-rotating magnetospheric convection |
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| Authors: | AJ Dessler BR Sandel SK Atreya |
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| Institution: | Department of Space Physics and Astronomy, Rice University, Houston, TX 77001 U.S.A.;Earth and Space Sciences Institute, University of Southern California, Tucson, AZ 85713 U.S.A.;Department of Atmospheric and Oceanic Science, University of Michigan, Ann Arbor, MI 48109 U.S.A. |
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| Abstract: | The hydrogen bulge is a feature in Jupiter's upper atmosphere that co-rotates with the planetary magnetic field (i.e. the hydrogen bulge is fixed in System III coordinates). It is located approximately 180° removed in System III longitude from the active sector, which has been identified as the source region for Jovian decametric radio emission and for release of energetic electrons into interplanetary space. According to the magnetic-anomaly model, the active sector is produced by the effect of the large magnetic anomaly in Jupiter's northern hemisphere. On the basis of the magnetic-anomaly model, it has been theoretically expected for some time that a two-cell magnetospheric convection pattern exists within the Jovian magnetosphere. Because the convection pattern is established by magnetic-anomaly effects of the active sector, the pattern co-rotates with Jupiter. (This is in contrast to the Earth's two-cell convection pattern that is fixed relative to the Sun with the Earth rotating beneath it.) The sense of the convection is to bring hot magnetospheric plasma into the upper atmosphere in the longitude region of the hydrogen bulge. This hot plasma contains electrons with energies of the order of 100keV that dissociate atmospheric molecules to produce the atomic hydrogen that creates the observed longitudinal asymmetry in hydrogen Lyman alpha emission. We regard the existence of the hydrogen bulge as the best evidence available thus far for the reality of the expected co-rotating magnetospheric convection pattern. |
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