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GEOPHYSICAL RESEARCH LETTERS, VOL. 7, NO. 10, PAGES 813–816, 1980

Detection of Energetic Hydrogen Molecules in Jupiter’s Magnetosphere by Voyager 2: Evidence for an Ionospheric Plasma Source

D. C. Hamilton

University of Maryland, Department of Physics and Astronomy, College Park, MD 20742

G. Gloeckler

University of Maryland, Department of Physics and Astronomy, College Park, MD 20742

S. M. Krimigis

Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD 20810

C. O. Bostrom

Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD 20810

T. P. Armstrong

Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66044

W. I. Axford

Max Planck Institut fur Aeronomie, D-3411 Katlenburg-Lindau 3, FGR

C. Y. Fan

Department of Physics, University of Arizona, Tucson, AZ 85721

L. J. Lanzerotti

Bell Telephone Laboratories, 600 Mountain Ave., Murray Hill, NJ 07974

D. M. Hunten

Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721

Abstract

We report the discovery of energetic ( ∼ 1 MeV/nuc) H₃ and H₂ molecules in Jupiter’s magnetosphere. The data, obtained with the LECP instrument on Voyager 2, showed these molecules to be present throughout the magnetosphere and as far as 180 R_J from the planet, in the “magnetospheric wind” region. Although the relative abundances of H₃ and H₂ do not show a monotonic trend with distance from Jupiter, the intervals of highest abundance were found in the outer magnetosphere. As an example, in the radial range 51-56 R_J of the dayside magnetosphere, the abundances of H₃ and H₂ (0.60-0.95 MeV/nuc) were about 20% and 13-25% that of He, respectively, and the He abundance was about 1-2% that of H. Since H₃ ⁺ is expected to be an important constituent of Jupiter’s ionopshere, our data provide strong evidence that, in addition to Io, the ionsphere may be an important local plasma source for the Jovian energetic particles. To our knowledge, the measurements reported here represent the first detection in nature of molecules at energies as high as 1 MeV/nucleon.

Received 2 June 1980; accepted 21 August 1980.

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Citation: Hamilton, D. C., G. Gloeckler, S. M. Krimigis, C. O. Bostrom, T. P. Armstrong, W. I. Axford, C. Y. Fan, L. J. Lanzerotti, and D. M. Hunten (1980), Detection of Energetic Hydrogen Molecules in Jupiter’s Magnetosphere by Voyager 2: Evidence for an Ionospheric Plasma Source, Geophys. Res. Lett., 7(10), 813–816.

Copyright 1980 by the American Geophysical Union.