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History of research on solar energetic particle (SEP) events: the evolving paradigm

Published online by Cambridge University Press:  01 September 2008

Edward W. Cliver
Edward W. Cliver*
Affiliation:
Space Vehicles Directorate, Air Force Research Laboratory email: afrl.rvb.pa@hanscom.af.mil
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Abstract

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Forbush initiated research on solar energetic particle (SEP) events in 1946 when he reported ionization chamber observations of the first three ground level events (GLEs). The next key development was the neutron monitor observation of the GLE of 23 February 1956. Meyer, Parker and Simpson attributed this high-energy SEP event to a short time-scale process associated with a solar flare and ascribed the much longer duration of the particle event to scattering in the interplanetary medium. Thus “flare particle” acceleration became the initial paradigm for SEP acceleration at the Sun. A more fully-developed picture was presented by the Australian radio astronomers Wild, Smerd, and Weiss in 1963. They identified two distinct SEP acceleration processes in flares: (1) the first phase accelerated primarily ~100 keV electrons that gave rise to fast-drift type III emission as they streamed outward through the solar atmosphere; (2) the second phase was produced by an outward moving (~1000 km s−1) magnetohydrodynamic shock, occurring in certain (generally larger) flares. The second phase, manifested by slow-drift metric type II emission, appeared to be required for substantial acceleration of protons and higher-energy electrons. This two-stage (or two-class) picture gained acceptance during the 1980s as composition and charge state measurements strengthened the evidence for two distinct types of particle events which were termed impulsive (attributed to flare-resident acceleration process(es)) and gradual (shock-associated). Reames championed the two-class picture and it is the commonly accepted paradigm today. A key error made in the establishment of this paradigm was revealed in the late 1990s by observations of SEP composition and charge states at higher energies (>10 MeV) than previously available. Specifically, some large and therefore presumably “gradual” SEP events looked “impulsive” at these energies. One group of researchers attributes these unusual events to acceleration of high-energy SEPs by flares and another school favors acceleration of flare seed particles by quasi-perpendicular shocks. A revised SEP classification scheme is proposed to accommodate the new observations and to include ideas on geometry and seed particle composition recently incorporated into models of shock acceleration of SEPs.

Keywords

SunSolar Energetic ParticlesHistory
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S257: Universal Heliophysical Processes , September 2008 , pp. 401 - 412
Copyright
Copyright © International Astronomical Union 2009

References

Axford, W. I. 1965, Planet. Space Sci., 13, 1301Google Scholar
Breneman, H. H. & Stone, E. C. 1985, ApJ (Lett.), 299, L57Google Scholar
Cane, H. V., McGuire, , & von Rosenvinge, T. T. 1986, ApJ, 301, 448CrossRefGoogle Scholar
Cane, H. V., Erickson, W. C., & Prestage, N. P. 2002, J. Geophys. Res., 107 (A10), CiteID 1315Google Scholar
Cane, H. V., von Rosenvinge, T. T., et al. 2003, Geophys. Res. Lett., 30 (12), CiteID 8017Google Scholar
Cane, H. V., Mewaldt, R. A., et al. 2006, J. Geophys. Res., 111 (A6), CiteID A06S90Google Scholar
Cliver, E. W. 1996, in High Energy Solar Physics, eds., Ramaty, R., Mandzhavidze, N., & Hua, X.-M., AIP, Woodbury, NY, vol. 374, p. 45Google Scholar
Cliver, E. W., Kahler, S. W., & Reames, D. V. 2004, ApJ, 605, 902Google Scholar
Cliver, E. W. 2006, ApJ, 639, 1206Google Scholar
Cliver, E. W. & Ling, A. G. 2007, ApJ, 658, 1349Google Scholar
Cliver, E. W. & Ling, A. G. 2009, ApJ, 690, 598CrossRefGoogle Scholar
Cliver, E. W. 2008a, in Particle Acceleration and Transport in the Heliosphere and Beyond, eds., Li, G., Hu, Q., Verkhoglyadova, O., Zank, G., Lin, R., & Luhmann, J., AIP, Melville, NY, vol. 1039, p. 190Google Scholar
Cliver, E. W. 2008b, Central European Astrophys. Bull. (in press)Google Scholar
Cohen, C. M. S., et al. 1999, Geophys. Res. Lett., 26, 2697Google Scholar
Forbush, S. E. 1946, Phys. Rev., 70, 771CrossRefGoogle Scholar
Forrest, D. J. & Chupp, E. L. 1983, Nature, 305, 291Google Scholar
Gopalswamy, N., et al. 2002, ApJ (Lett.), 572, L103Google Scholar
Hsieh, K. C. & Simpson, J. A. 1970, ApJ (Lett.), 162, L191Google Scholar
Hudson, H. S. & Cliver, E. W. 2001, J. Geophys. Res., 106, 25199Google Scholar
Jokipii, J. R. & Parker, E. N. 1968, Phys. Rev. Lett., 21, 44Google Scholar
Kahler, S. W., Hildner, E., & Van Hollebeke, M. A. I. 1978, Solar Phys., 57, 429Google Scholar
Kahler, S., Reames, D. V., et al. 1985, ApJ, 290, 742Google Scholar
Kalher, S. W., Reames, D. V., & Sheeley, N. R. Jr., 2001, ApJ, 562, 558Google Scholar
Kallenrode, M.-B., Cliver, E. W., & Wibberenz, G. 1992, ApJ, 391, 370Google Scholar
Kanbach, G. O., et al. 1993, Aston. Astrophys. Suppl., 97, 349Google Scholar
Klecker, B., Hovestadt, D., et al. 1984, ApJ, 281, 458Google Scholar
Lange, I. & Forbush, S. E. 1942a, Terr. Mag., 47, 185Google Scholar
Lange, I. & Forbush, S. E. 1942b, Terr. Mag., 47, 331Google Scholar
Lee, M. A. 2005, ApJS, 158, 38Google Scholar
Lin, R. P. 1970, Solar Phys., 12, 266Google Scholar
Mason, G. M., Reames, D. V., et al. 1986, ApJ, 303, 849CrossRefGoogle Scholar
Mason, G. M., et al. 2002, ApJ, 574, 1039Google Scholar
Mazur, J. E., Mason, G. M., et al. 1999, Geophys. Res. Lett., 26, 173Google Scholar
Meyer, P., Parker, E. N., & Simpson, J. A. 1956, Phys. Rev., 104, 768Google Scholar
Moses, D., Dröge, W., Meyer, P., & Evenson, P. 1989, ApJ, 346, 523Google Scholar
Nitta, N. V., Cliver, E. W., & Tylka, A. J. 2003, ApJ (Lett.), 586, L103Google Scholar
Ramaty, R., Murphy, R. J., & Dermer, C. D. 1987, ApJ (Lett.), 216, L41Google Scholar
Reames, D. V., von Rosenvinge, T. T., & Lin, R. P. 1985, ApJ, 292, 716Google Scholar
Reames, D. V., Stone, R. G., & Kallenrode, M.-B. 1991, ApJ, 380, 287Google Scholar
Reames, D. V. 1993, Adv. Sp. Res., 13 (9), 331Google Scholar
Reames, D. V. 1999, Space Sci. Revs, 90, 413Google Scholar
Reid, G. C. 1964, J. Geophys. Res., 69, 2659Google Scholar
Ryan, J. M. 2000, Space Sci. Revs, 93, 581Google Scholar
Tsurutani, B. T., and Lin, R. P. 1985, J. Geophys. Res., 90, 1CrossRefGoogle Scholar
Tylka, A. J., et al. 2005, ApJ, 625, 474Google Scholar
Tylka, A. J., et al. 2006, ApJS, 164, 536Google Scholar
Tylka, A. J. & Lee, M. A. 2006, ApJ, 646, 1319Google Scholar
Wild, J. P., Smerd, S. F., & Weiss, A. A. 1963, ARAA, 1, 291Google Scholar
Zhang, J., Dere, K. P., Howard, R. A., Kundu, M. R., & White, S. M. 2001, ApJ, 561, 396Google Scholar