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Published December 15, 1989 | public
Journal Article

Energetic Charged Particles in the Magnetosphere of Neptune

Abstract

The Voyager 2 cosmic ray system (CRS) measured significant fluxes of energetic [≳ 1 megaelectron volt (MeV)] trapped electrons and protons in the magnetosphere of Neptune. The intensities are maximum near a magnetic L shell of 7, decreasing closer to the planet because of absorption by satellites and rings. In the region of the inner satellites of Neptune, the radiation belts have a complicated structure, which provides some constraints on the magnetic field geometry of the inner magnetosphere. Electron phase-space densities have a positive radial gradient, indicating that they diffuse inward from a source in the outer magnetosphere. Electron spectra from 1 to 5 MeV are generally well represented by power laws with indices near 6, which harden in the region of peak flux to power law indices of 4 to 5. Protons have significantly lower fluxes than electrons throughout the magnetosphere, with large anisotropies due to radial intensity gradients. The radiation belts resemble those of Uranus to the extent allowed by the different locations of the satellites, which limit the flux at each planet.

Additional Information

© 1989 American Association for the Advancement of Science. Received 31 October 1989; accepted 15 November 1989. We thank R. E. Vogt for his contributions during his tenure as principal investigator for the CRS system on Voyager 2. We thank the Voyager project members and the enthusiastic staff of our laboratories at Caltech and Goddard Space Flight Center for their excellent support; special thanks go to P. Schuster, R. Kaiper, R. McGuire, T. Garrard, B. Gauld, R. Burrell, and O. Divers. Thanks also to P. Liggett, L. Lee, C. Byrne, S. Burleigh, and the rest of the VNESSA staff at the Jet Propulsion Laboratory. Supported by NASA under contracts NAS7-918 and NGR 05-002-160.

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023