Il Nuovo Cimento C

, Volume 6, Issue 2, pp 145–158 | Cite as

The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

  • N. Iucci
  • M. Parisi
  • M. Storini
  • G. Villoresi
Article

Summary

The cosmic-ray equatorial anisotropy inside broad high-speed solar-wind streams ejected by coronal holes,i.e. in quasi-stationary condition, is analysed over the years 1973–1974. From the beginning to the end of the stream the amplitudes of the first and second harmonics of the anisotropy are found to decrease remarkably by factors 2.5 and 2.0, respectively, while the phases do not show systematic variations. The development of the stream structure in the interplanetary space together with the Parker theory on the diurnal anisotropy in stationary condition give a plausible explaination for the large variation observed in the first harmonic of the anisotropy. The behaviour of the second harmonic is tentatively interpreted in the light of current theories.

PACS. 94.40

Cosmic rays 

Riassunto

Si analizza l'anisotropia equatoriale dei raggi cosmici galattici in condizioni quasi stazionarie all'interno di estesi flussi veloci di vento solare emessi da buchi coronali (RHSSs), durante gli anni 1973–1974. Si trova che le ampiezze della prima e della seconda armonica dell'anisotropia diminuiscono considerevolmente dall'inizio alla fine del RHSS, rispettivamente di 2.5 e di 2.0, mentre le fasi non mostrano variazioni sistematiche. L'evoluzione della struttura del RHSS nello spazio interplanetario insieme con la teoria di Parker sull'effetto diurno in condizioni stazionarie fornisce una possibile spiegazione della grande variazione osservata nella prima armonica dell'anisotropia equatoriale. Si tenta inoltre d'interpretare l'andamento della seconda armonica alla luce delle teorie correnti.

Резюме

Анализируется экваториальная анизотропия космических лучей, зарегистрированная в течение 1973–1974 г.г. внутри широких быстрых потоков солнечного ветра, испускаемых корональными дырами, т.е. при квазистационарном условии. Обнаружено, что от начала к концы потока амплитуда первой и второй гармоник анизотропии существенно уменьшается соответственно в 2.5 и 2 раза, тогда как фазы не обнаруживают систематических изменений. Анализ структуры потока в межпланетном пространстве вместе с теорией Паркера для суточной анизотропии при стационарном условии дает правдоподобное объяснение для больших изменений, наблюденных в первой гармоники анизотропии. Интерпретируется поведение второй гармоники в свете имеющихся теорий.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. (1).
    M. A. Pomerantz andS. P. Duggal:Space Sci. Rev.,12, 75 (1971).ADSCrossRefGoogle Scholar
  2. (2).
    S. E. Forbush:J. Geophys. Res.,78, 7933 (1973).ADSCrossRefGoogle Scholar
  3. (3).
    A. G. Ananth, S. P. Agrawal andU. R. Rao:Pramana,3, 74 (1974).ADSCrossRefGoogle Scholar
  4. (4).
    E. N. Parker:Planet. Space Sci.,12, 735 (1964).ADSCrossRefGoogle Scholar
  5. (5).
    D. Stern:Planet. Space Sci.,12, 973 (1964).ADSCrossRefGoogle Scholar
  6. (6).
    U. R. Rao:Space Sci. Rev.,12, 719 (1972).ADSCrossRefGoogle Scholar
  7. (7).
    N. Iucci andM. Storini:Nuovo Cimento B,13, 361 (1973).ADSCrossRefGoogle Scholar
  8. (8).
    W. I. Axford:Planet. Space Sci.,13, 115 (1965).ADSCrossRefGoogle Scholar
  9. (9).
    J. B. Zirker, Editor:Coronal Holes and High Speed Wind Streams—A Monograph from Skylab Solar Workshop I (Boulder, Colo, 1977).Google Scholar
  10. (10).
    J. T. Gosling, J. R. Asbridge, S. J. Bame andW. C. Feldman:J. Geophys. Res.,83, 1401 (1978).ADSCrossRefGoogle Scholar
  11. (11).
    E. J. Smith andJ. H. Wolfe:Proceedings of COSPAR Symposium B, Tel-Aviv, June 1977, edited byM. A. Shea, D. F. Smart andS. T. Wu (Hanscom, Mass., 1977), p. 227.Google Scholar
  12. (12).
    N. Iucci, M. Parisi, M. Storini andG. Villoresi:Nuovo Cimento C,2, 421 (1979).ADSCrossRefGoogle Scholar
  13. (13).
    E. C. Roelof, R. E. Gold, A. S. Krieger, J. T. Nolte andD. Venkatesan:Proceedings of the XIV International Conference on Cosmic Rays, Vol.4 (Munich, 1975), p. 1138.ADSGoogle Scholar
  14. (14).
    T. Murayama:Proceedings of the XIV International Conference on Cosmic Rays, Vol.4 (Munich, 1975), p. 1144.ADSGoogle Scholar
  15. (15).
    N. R. Sheeley jr., J. W. Harvey andW. C. Feldman:Sol. Phys.,49, 271 (1976).ADSCrossRefGoogle Scholar
  16. (16).
    S. P. Agrawal:J. Geophys. Res.,86, 10115 (1981).ADSCrossRefGoogle Scholar
  17. (17).
    J. H. King:Interplanetary Medium Data Book, NSSDC/WDC-A-R & S 77-04 (Greenbelt, Md., 1977).Google Scholar
  18. (18).
    M. D. Wilson andM. Bercovitch:Cosmic Ray NM-64Neutron Monitor Data Reports, NRCL (Ottawa, Ont.).Google Scholar
  19. (19).
    H. S. Ahluwalia:Proceedings of the International Cosmic Ray Symposium on High Energy Cosmic Ray Modulation (Tokyo, 1976), p. 260.Google Scholar
  20. (20).
    H. Elliot:Proceedings of the XVI International Conference on Cosmic Rays, Vol.14 (Kyoto, 1979), p. 200.ADSGoogle Scholar
  21. (21).
    J. J. Quenby andB. Lietti:Planet. Space Sci.,16, 1209 (1968).ADSCrossRefGoogle Scholar
  22. (22).
    K. Nagashima, K. Fujimoto, Z. Fujii, H. Ueno andI. Kondo:Rep. Ionos. Space Res. Jpn.,26, 31 (1972).ADSGoogle Scholar
  23. (23).
    J. Kota:Proceedings of the XVI International Conference on Cosmic Rays, Vol.4 (Kyoto, 1979), p. 137.ADSGoogle Scholar

Copyright information

© Società Italiana di Fisica 1983

Authors and Affiliations

  • N. Iucci
    • 1
  • M. Parisi
    • 2
    • 3
  • M. Storini
    • 2
    • 3
  • G. Villoresi
    • 2
    • 3
  1. 1.Dipartimento di FisicaUniversità «La Sapienza»Roma
  2. 2.Istituto di Fisica dello Spazio Interplanetario del C.N.R.Roma
  3. 3.Reparto Raggi Cosmici, c/o Istituto di Fisica «G. Marconi»Roma

Personalised recommendations