Abstract
Evidence is given that the particle acceleration in flares is confined to the initial phase of the flare development preceding the Hα flare maximum and lasting for less than 10 min. The impulsive acceleration process is confined to a relatively small limited volume of about 5 × 1027 cm3 in the region of highest magnetic gradient in the flare, and its size represents about 0.05 or less of the total extent of the hot condensation which produces the soft X-ray and gradual microwave bursts. About one in fifty particles in this volume is accelerated to energy exceeding 100 keV, the total particle density being ≈ 1010 cm−3. The accelerated electrons produce the impulsive hard X-ray burst, but synchrotron losses greatly reduce the number of relativistic electrons participating in the bremsstrahlung process. Protons above 20 MeV penetrate to the lowest chromosphere and upper photosphere and temporarily increase the temperature in the bombarded region. As the result a flash of continuous emission appears, which should be most expressive below 1527 Å. The associated white-light emission shows the bottom of the region where the impulsive acceleration process occurs.
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References
Angle, K.: 1962, Publ. Astron. Soc. Pacific 73, 227.
Arnoldy, R. L., Kane, S. R., and Winckler, J. R.: 1968, Astrophys. J. 151, 711.
Becker, U.: 1958, Z. Astrophys. 46, 168.
Cline, T. L. and McDonald, F. B.: 1968, Solar Phys. 5, 507.
Cline, T. L., Holt, S. S., and Hones, E. W., Jr.: 1968, J. Geophys. Res. 73, 434.
D'Azambuja, M.: 1947, Astronomie 61, 114.
De Jager, C.: 1965, in: Astronomical Observations from Space Vehicles (ed. by J.-L. Steinberg), Int. Astron. Union Symp. vol. 23, p. 45.
De Jager, C.: 1969, in Solar Flares and Space Research (ed. by C. de Jager and Z. Švestka), p. 1.
De Mastus, H. L. and Stover, R. R.: 1967, Publ. Astron. Soc. Pacific 79, 615.
Dobbie, J. C., Moss, W., and Thackeray, A. D.: 1938, Monthly Notices Roy. Astron. Soc. 98, 606.
Ellison, M. A.: 1952, Publ. Roy. Obs. Edinburgh 1, 75.
Friedman, H.: 1969, in Solar Flares and Space Research (ed. by C. de Jager and Z. Švestka), p. 87.
Fritzová-Švestková, L. and Švestka, Z.: 1966, Bull. Astron. Inst. Czech. 17, 249.
Gingerich, O. and De Jager, C.: 1968, Solar Phys. 3, 5.
Gordon, I. M.: 1954, Doklady AN SSSR 94, 813.
Heristchi, D., Kangas, J., Kremser, G., Legrand, J. P., Masse, P., Palous, M., Pfotzer, G., Riedler, W., and Wilhelm, K.: 1969, Annals of IQSY 3, 267.
Holt, S. S. and Cline, T. L.: 1968, Astrophys. J. 154, 1027.
Holt, S. S. and Ramaty, R.: 1969, Solar Phys. 8, 119.
Jauch, J. M. and Rohrlich, F.: 1955, The Theory of Photons and Electrons, Addison-Wesley, Cambridge, Mass.
Kane, S. R.: 1969, Astrophys. J. 169, L139.
Korchak, A. A.: 1967, Soviet Astron. 11, 258.
Křivský, L.: 1963, Bull. Astron. Inst. Czech. 14, 77.
Křivský, L.: 1965, Bull. Astron. Inst. Czech. 16, 27.
Křivský, L.: 1966, Bull. Astron. Inst. Czech. 17, 141.
Křivský, L.: 1969, Bull. Astron. Inst. Czech. 20, 163.
Křivský, L. and Švestka, Z.: 1970, Space Res. 10 (in press).
McClinton, A. T.: 1968, NRL Space Research Seminar, April 17, 1968, p. 63.
Monsignori Fossi, B. C., Poletto, G., and Tagliaferri, G. L.: 1969, Solar Phys. 10, 196.
Moreton, G. E.: 1964, AAS-NASA Symp. on the Physics of Solar Flares, p. 209.
Mustel, E. R.: 1955, Izv. Krymsk. Astrofiz. Observ. 15, 54.
Nagasawa, S., Takakura, T., Tsuchiyi, A., Tanaka, H., and Koyama, H.: 1961, Publ. Astron. Soc. Japan 13, 129.
Notuki, M., Hatanaka, T., and Unno, W.: 1956, Publ. Astron. Soc. Japan 8, 52.
Ohki, K. I.: 1969, Solar Phys. 7, 260.
Schatzman, E.: 1965, in The Solar Spectrum (ed. by C. de Jager), D. Reidel Publ. Comp., Dordrecht, p. 313.
Severny, A. B.: 1957, Izv. Krymsk. Astrofiz. Observ. 17, 129.
Stein, W. A. and Ney, E. P.: 1963, J. Geophys. Res. 68, 65.
Švestka, Z.: 1966a, Bull. Astron. Inst. Czech. 17, 137.
Švestka, Z.: 1966b, Space Sci. Rev. 5, 388.
Švestka, Z. and Simon, P.: 1969, Solar Phys. 10, 3.
Takakura, T.: 1960, Publ. Astron. Soc. Japan 12, 352.
Takakura, T.: 1969, Solar Phys. 6, 133.
Takakura, T. and Kai, K.: 1966, Publ. Astron. Soc. Japan 18, 57.
Valníček, B.: 1967, Bull. Astron. Inst. Czech. 18, 249.
Zirin, H. and Russo Lackner, D.: 1969, Solar Phys. 6, 86.
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Švestka, Z. The phase of particle acceleration in the flare development. Sol Phys 13, 471–489 (1970). https://doi.org/10.1007/BF00153567
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DOI: https://doi.org/10.1007/BF00153567