Abstract
The probable connection between cosmic rays and the electromagnetic state of the interplanetary medium was recognized by Hannes Alfvén as early as 1949 (Alfvén, 1949, 1950); he pointed out that the properties of cosmic rays necessitate a mechanism, external to Earth but within the solar system, capable of accelerating particles to extremely high energies. In advocating the view of local origin for part of the cosmic-ray spectrum, Alfvén and his colleagues developed a very general type of acceleration mechanism called ‘magnetic pumping’. The unique data set of the two Voyagers extends over an entire decade (1977–1987) and is most suitable to explore the problem of acceleration of charged particles in the heliosphere. The energy coverage of the Low Energy Charged Particle (LECP) experiment covers the range ∼30 keV to several hundred MeV for ions and ∼22 keV to several MeV for electrons. Selected observations of interplanetary acceleration events from ∼1 to ∼25 AU are presented and reviewed. These show frequent acceleration of ions to several tens of MeV in association with shocks; highest energies (≳220 MeV oxygen) were measured in the near-perpendicular (θ Bn ≃87.5°) shock of January 5, 1978 at ∼1.9 AU, where electron acceleration was also observed. Examples of ion acceleration in association with corotating interaction regions are presented and discussed. It is shown that shock structures have profound effects on high-energy (≥70 MeV) cosmic rays, especially during solar minimum, when a negative latitudinal gradient was observed after early 1985 at all energies from ∼70 MeV down to ∼30 keV. By early 1987, most shock acceleration activity in the outer heliosphere (∼25 to 30 AU) had ceased both in the ecliptic (Voyager-2) and at higher (∼30°) ecliptic latitudes (Voyager-1). The totality of observations demonstrate that local acceleration to a few hundred MeV, and as high as a few GeV is continually present throughout the heliosphere. It should be noted that in 1954 when Alfvén suggested local acceleration and containment of cosmic rays within the solar system, no one treated his suggestion seriously, at any energy. The observations reviewed in this paper illustrate once more Alfvén's remarkable prescience and demonstrate how unwise it is to dismiss his ideas.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Akasofu, S.-I. and Hakamada, K.: 1983,Geophys. Res. Letters 7, 577.
Alfvén, H.: 1949,Phys. Rev. 75, 1732.
Alfvén, H.: 1950,Phys. Rev. 77, 375.
Alfvén, H.: 1954a,Nuovo Cimento Suppl. 11, No. 2.
Alfvén, H.: 1954b,Tellus 6, 232.
Alfvén, H.: 19659,Tellus 11, 106.
Armstrong, T. P., Chen, G., Sarris, E. T., and Krimigis, S. M.: 1977, ‘Acceleration and Modulation of Electrons and Ions by Propagating Interplanetary Shocks’, in M. A. Shea et al. (eds.),Study of Travelling Interplanetary Phenomena, D. Reidel Publ. Co., Dordrecht, Holland, pp. 367–389.
Bavassano, B., Smith, E. J., and Tsurutani, B. T.: 1987,J. Geophys. Res. 92, 285.
Bryant, D. A., Cline, T. L., Desai, U. D., and MacDonald, F. B.: 1962,J. Geophys. Res. 67, 4983.
Decker, R. B.: 1983,J. Geophys. Res. 88, 9959.
Decker, R. B., Krimigis, S. M., and Venkatesan, D.: 1987,J. Geophys. Res. 92, 3375.
Decker, R. B., Pesses, M. E., and Krimigis, S. M.: 1981,J. Geophys. Res. 86, 8819.
Duggal, S. P.: 1979,Rev. Geophys. Space Phys. 17, 1021.
Fälthammar, C.-G.: 1963, ‘Acceleration of Cosmic-Ray Particles by Magnetic Pumping’, in B. Peters (ed.),Proc. International School of Physics ‘Enrico Fermi’, Course XIX, Academic Press, New York, p. 99.
Fisk, L. A.: 1976,J. Geophys. Res. 81, 4646.
Gold, R. E., Decker, R. B., Krimigis, S. M., Lanzerotti, L. J., and Maclennan, C. G.: 1988,J. Geophys. Res. 93 (in press).
Goldstein, M. L., Fisk, L. A., and Ramaty, R.: 1970,Phys. Rev. Letters 25, 832.
Kennel, C. F., Coroniti, F. V., Scarf, F. L., Livesey, W. A., Russell, C. T., Smith, E. J., Wenzel, K. P., and Scholer, M.: 1986,J. Geophys. Res. 91, 11917.
Krimigis, S. M. and Sarris, E. T.: 1985, ‘Acceleration of Ions and Electrons to Near Cosmic-Ray Energies in a Perpendicular Shock: The January 6, 1987 Event',Proceedings 19th International Conference of Cosmic Rays, pp. 170–173.
Krimigis, S. M., Armstrong, T. P., Axford, W. I., Bostrom, C. O., Fan, C. Y., Gloeckler, G., and Lanzerotti, L. J.: 1977,Space Sci. Rev. 21, 329.
Krimigis, S. M., Zwickl, R. D., and Baker, D. N.: 1985,J. Geophys. Res. 89, 3947.
Levy, E. H., Duggal, S. P., and Pomerantz, M. A.: 1976,J. Geophys. Res. 81, 51.
Lockwood, J. A., Webber, W. R., and Jokipii, J. R.: 1986,J. Geophys. Res. 91, 2851.
Perko, J. S. and Burlaga, L. F.: 1987,J. Geophys. Res. 92, 6127.
Pesses, M. E.: 1981,J. Geophys. Res. 86, 150.
Pomerantz, M. A. and Duggal, S. P.: 1974,J. Geophys. Res. 79, 913.
Potter, D. W.: 1981,J. Geophys. Res. 86, 11111.
Pyle, K. R. and Simpson, J. A.: 1977,Astrophys. J. 215, L89.
Rosner, R., Chupp, E. L., Gloeckler, G., Gorney, D. J., Krimigis, S. M., Mok, Y., Ramaty, R., Swift, D. W., Vlahos, L., and Zweibel, E. G.: 1984, ‘Particle Acceleration’, in D. Butler and K. Papadopoulos (eds.),Solar-Terrestrial Physics: Present and Future, NASA-RP-1120.
Sarris, E. T. and Krimigis, S. M.: 1985,Astrophys. J. 298, 676.
Sarris, E. T., Anagnostopoulos, G. C., and Trochoutsos, P. C.: 1984,Solar Phys. 93, 195.
Sarris, E. T., Dodopoulos, C. A., and Venkatesan, D.: 1987a, ‘East-West Asymmetry of Solar Flare Shock Effects on High Energy Particles (E≳30 MeV)’, presented at the20th International Cosmic Ray Conference, Moscow, SH7.2-5, August 1987.
Sarris, E. T., Krimigis, S. M., and Decker, R. B.: 1987b, ‘Evolution of Shock-Associated Energetic Ion Enhancements between Closely Separated Spacecraft’, presented atSolar Wind 5 Conference, Boulder (CO), August 24–28.
Sarris, E. T., Krimigis, S. M., and Armstrong, T. P.: 1976,Geophys. Res. Letters 3, 133.
Smith, E. J. and Wolfe, J. H.: 1979,Space Sci. Rev. 23, 217.
Venkatesan, D., Decker, R. B., Krimigis, S. M., and Van Allen, J. A.: 1985,J. Geophys. Res. 90, 2905.
Venkatesan, D., Decker, R. B., and Krimigis, S. M.: 1987, ‘Cosmic-Ray Intensity Gradients During 1984–'86’, SH6.3-5,Proc. 20th Int. Cosmic Ray Conf. Moscow, U.S.S.R., August 2–13, pp. 385–388.
Webber, W. R., Lockwood, J. A., and Jokipii, J. R.: 1986,J. Geophys. Res. 91, 4103.
Zwickl, R. D., Krimigis, S. M., Carbary, J. F., Keath, E. P., Armstrong, T. P., Hamilton, D. C., and Gloeckler, G.: 1981,J. Geophys. Res. 86, 8125.
Author information
Authors and Affiliations
Additional information
Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.
Rights and permissions
About this article
Cite this article
Krimigis, S.M., Venkatesan, D. In situ acceleration and gradients of charged particles in the outer solar system observed by the voyager spacecraft. Astrophys Space Sci 144, 463–486 (1988). https://doi.org/10.1007/BF00793199
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00793199