Portal de Periódicos da CAPES

The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io

1974; American Geophysical Union; Volume: 79; Issue: 25 Linguagem: Inglês

10.1029/ja079i025p03522

2156-2202

J. A. Simpson, D. C. Hamilton, R. B. McKibben, A. Mogro‐Campero, K. R. Pyle, A. J. Tuzzolino,

Solar and Space Plasma Dynamics

Journal of Geophysical Research (1896-1977)Volume 79, Issue 25 p. 3522-3544 The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io J. A. Simpson, J. A. SimpsonSearch for more papers by this authorD. C. Hamilton, D. C. HamiltonSearch for more papers by this authorR. B. McKibben, R. B. McKibbenSearch for more papers by this authorA. Mogro-Campero, A. Mogro-CamperoSearch for more papers by this authorK. R. Pyle, K. R. PyleSearch for more papers by this authorA. J. Tuzzolino, A. J. TuzzolinoSearch for more papers by this author J. A. Simpson, J. A. SimpsonSearch for more papers by this authorD. C. Hamilton, D. C. HamiltonSearch for more papers by this authorR. B. McKibben, R. B. McKibbenSearch for more papers by this authorA. Mogro-Campero, A. Mogro-CamperoSearch for more papers by this authorK. R. Pyle, K. R. PyleSearch for more papers by this authorA. J. Tuzzolino, A. J. TuzzolinoSearch for more papers by this author First published: 1 September 1974 https://doi.org/10.1029/JA079i025p03522Citations: 98AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract The University of Chicago experiment on board the Pioneer 10 spacecraft contains four sensor systems, three of which were used to study the trapped radiation region R < 20 RJ. Two of the systems are of novel design. One is a silicon detector operated in the current mode surrounded by sufficient beryllium to stop protons with energies ⪝30 MeV. Electrons with energies ⪞3 MeV were measured by this detector over an intensity dynamic range of >107. Because of the great difficulty in identifying high-energy protons in the presence of an intense high-energy electron component, ⪞35-MeV protons were measured by proton-induced nuclear fission of 232Th. The third detector system was a telescope measuring 0.5- to 1.8-MeV/nucleon proton and helium nuclei and their angular distributions. The paper contains a detailed analysis of electrons ⪞3 MeV and of protons 0.5–1.8 MeV and ⪞35 MeV for both the inbound and the outbound passes of the spacecraft. The analyses were carried out for the two different models for the Jovian magnetic field reported since the flyby of Pioneer 10, namely, the D1 and D2 models of Smith et al. (1974a, b). We have used the D2 model in all figures and calculations in this paper and have represented our data in terms of magnetic shell parameter L. We report the L dependence of fluxes of protons with energies ≅1 MeV and ⪞35 Mev and of electrons with energies ⪞3 MeV for the region L ⪝ 25. We also report the dependence of these fluxes on magnetic latitude. We find maximum fluxes for ⪞35-MeV protons of ∼6×106 protons cm−2 s−1 at L ≅ 3.4 and for ⪞3-MeV electrons of ∼2.5×108 el cm−2 s−1 at L ≅ 3.1. From our analysis we find (1) conclusive evidence that the trapped radiation in Jupiter's inner magnetosphere is maintained and supplied by inward diffusion from the outer regions of the trapped radiation zone, (2) that the time required for isotropization of an anisotropic flux by pitch angle scattering inside L ≅ 6 is long in comparison with the time required for particles to diffuse inward from L ≅ 6 to L ≅ 3, (3) that the high-energy protons were not injected at high energies by the Crand (cosmic ray albedo neutron decay) process but were accelerated in the magnetosphere of Jupiter, and (4) that the main conclusions of our analysis are unaffected by use of either the D1 or the D2 magnetic field models. We have carried out theoretical studies of the capture of trapped electrons and protons by Io, and we find that the probability of capture by Io depends strongly upon the particle species and kinetic energy. From observations of the 0.5- to 1.8-MeV proton flux near the orbit of Io we obtain a probable value for the radial diffusion coefficient of κ ≅ 6 × 10−8 RJ² s−1 at L ≅ 6. This diffusion coefficient is large enough that no new sources of particles inside the orbit of Io are required to explain the existence of the high fluxes of relativistic electrons inferred to exist at L ≅ 2 from radio observations. An unexpected result of our observations is the discovery of a decrease toward low L in the intensity of ⪞35-MeV and 1-MeV protons inside L ≅ 3.5, so that the maximum flux of protons observed both inbound and outbound occurred at L ≅ 3.5. We discuss the possible causes of this effect. References Bame, S. J., A. J. Hundhausen, J. R. Asbridge, I. B. Strong, Solar wind ion composition, Phys. Rev. Lett., 20, 393, 1968. Birmingham, T., W. N. Hess, T. Northrop, R. Baxter, M. Lojko, The electron diffusion coefficient in Jupiter's magnetosphere, J. Geophys. Res., 79, 87, 1974. Brice, N., Energetic protons in Jupiter's radiation belts, Proceedings of the Jupiter Radiation Belt WorkshopTech. Mem. 33-543, 283Jet Propul. Lab., Pasadena, Calif.July, 1972. Brice, N., T. R. McDonough, Jupiter's radiation belts, Icarus, 18, 206, 1973. Brown, W. L., Energetic outer belt electrons at synchronous altitude, Earth's Particles and Fields B. M. McCormac, 33, Reinhold, New York, 1968. Brown, R. A., F. H. Chaffee, High resolution spectra of sodium emission from Io, Astrophys. J. Lett., 187, L125, 1974. Clarke, J. N., A synchrotron model for the decimetric radiation of Jupiter, Radio Sci., 5, 529, 1970. Coroniti, F. V., C. F. Kennel, R. M. Thorne, Stably trapped proton fluxes in the Jovian magnetosphere, Astrophys. J., 189, 383, 1974. Divine, N., Post-workshop models of Jupiter's radiation belts, Proceedings of the Jupiter Radiation Belt WorkshopTech. Mem. 33-543, 527Jet Propul. Lab., Pasadena, Calif.July, 1972. Fillius, R. W., C. E. Mcllwain, Radiation belts of Jupiter, Science, 183, 314, 1974. Fritz, T. A., D. J. Williams, Initial observations of geomagnetically trapped alpha particles at the equator, J. Geophys. Res., 78, 4719, 1973. Gurnett, D. A., Sheath effects and related charged particle acceleration by Jupiter's satellite Io, Astrophys. J., 175, 525, 1972. Hall, C. F., Pioneer 10, Science, 183, 301, 1974. Hess, W. N., T. J. Birmingham, G. D. Mead, Jupiter's radiation belts: Can Pioneer 10 survive?, Science, 182, 1021, 1973. Hess, W. N., T. J. Birmingham, G. D. Mead, Absorption of trapped particles by Jupiter's moons, J. Geophys. Res., 79, 2877, 1974. Hubbard, R. F., S. D. Shawhan, G. Joyce, Io as an emitter of 100-keV electrons, J. Geophys. Res., 79, 920, 1974. Hundhausen, A. J., Composition and dynamics of the solar wind plasma, Rev. Geophys. Space Phys., 8, 729, 1970. Ioannidis, G., N. Brice, Plasma densities in the Jovian magnetosphere: Plasma slingshot or Maxwell demon?, Icarus, 14, 360, 1971. Jacques, S. A., L. Davis Jr., Diffusion models for Jupiter's radiation belt., reportDowns Lab., Calif, Inst. of Technol., Pasadena, 1972. Judge, D. L., R. W. Carlson, Pioneer 10 observations of the ultraviolet glow in the vicinity of Jupiter, Science, 183, 317, 1974. Kennel, C., Stably trapped proton limits for Jupiter, Proceedings of the Jupiter Radiation Belt WorkshopTech. Mem. 33-543, 347Jet Propul. Lab., Pasadena, Calif.July, 1972. Kliore, A., D. L. Cain, G. Fjeldbo, B. L. Seidel, Preliminary results on the atmospheres of Io and Jupiter from the Pioneer 10 S-band occultation experiment, Science, 183, 323, 1974. Krimigis, S. M., J. A. Van Allen, Geomagnetically trapped alpha particles, J. Geophys. Res., 72, 5779, 1967. McElroy, M. B., Y. L. Yung, R. A. Brown, Sodium emission from lo: Implications, Astrophys. J. Lett., 187, L127, 1974. Mead, G. D., Magnetic coordinates for the Pioneer l0 Jupiter encounter, J. Geophys. Res., 79, 3514, 1974. Mead, G. D., W. N. Hess, Jupiter's radiation belts and the sweeping effect of its satellites, J. Geophys. Res., 78, 2793, 1973. Shawhan, S. D., D. A. Gurnett, R. F. Hubbard, G. Joyce, Io-accelerated electrons: Predictions for Pioneer l0 and Pioneer ll, Science, 182, 1348, 1973. Simpson, J. A., D. Hamilton, G. Lentz, R. B. McKibben, A. Mogro-Campero, M. Perkins, K. R. Pyle, A. J. Tuzzolino, J. J. O'Gallagher, Protons and electrons in Jupiter's magnetic field, Results from the University of Chicago experiment on Pioneer 10, Science, 183, 306, 1974. Smith, E. J., L. Davis Jr., D. E. Jones, D. S. Colburn, P. J. Coleman Jr., P. Dyal, C. P. Sonett, Magnetic field of Jupiter and its interaction with the solar wind, Science, 183, 305, 1974a. Smith, E. J., L. Davis Jr., D. E. Jones, P. J. Coleman, D. S. Colburn, P. Dyal, C. P. Sonett, A. M. A. Frandsen, The planetary magnetic field and magnetosphere of Jupiter, J. Geophys. Res., 79, 3501, 1974b. Thomas, J., W. R. Doherty, Calculations of neutron-decay-proton trapping in the Jovian magnetosphere, Proceedings of the Jupiter Radiation Belt WorkshopTech. Mem. 33-543, 315Jet Propul. Lab., Pasadena, Calif.July, 1972. Thorne, K. S., Dependence of Jupiter's decimeter radiation on the electron distribution in its Van Allen radiation belts, Radio Sci., 690, 1557, 1965. Trainor, J. H., B. J. Teegarden, D. E. Stilwell, F. B. McDonald, E. C. Roelof, W. R. Webber, Energetic particle population in the Jovian magnetosphere: A preliminary note, Science, 183, 311, 1974. Van Allen, J. A., B. A. Randall, S. M. Krimigis, Energetic carbon, nitrogen, and oxygen nuclei in the earth's outer radiation zone, J. Geophys. Res., 75, 6085, 1970. Van Allen, J. A., D. N. Baker, B. A. Randall, M. F. Thomsen, D. D. Sentman, H. R. Flindt, Energetic electrons in the magnetosphere of Jupiter, Science, 183, 309, 1974. Citing Literature Volume79, Issue25Space Physics1 September 1974Pages 3522-3544 ReferencesRelatedInformation