Abstract
Energetic electrons, with energies 10–100 keV, accelerated during the impulsive phase of solar flares, sometimes encounter increasing magnetic fields as they stream towards the chromosphere. A consequence of the conservation of their magnetic moment is that the electrons with large initial pitch angle will be reflected at different heights from the atmosphere. Energetic electrons reflected below the transition zone will lose most of their energy to collisions and will never return to the corona. Thus, electrons reflected above the transition zone form a loss-cone velocity distribution which can be unstable to Electron Cyclotron Maser (ECM). The interaction of quasi-perpendicular shocks with the ambient coronal plasma will form a ‘ring’ or ‘hollow beam’ velocity distribution upstream of the shock. ‘Ring’ velocity distributions are also unstable to the ECM instability. A review of the recent results on the theory of ECM will be presented. We will focus our discussion on the questions: (a) What are the characteristics of the linear growth rate of the ECM during solar flares? (b) How does the ECM saturate and what is its efficiency? (c) How does the ECM generated radiation modify the flare environment? Finally we will review the outstanding questions in the theory of ECM and we will relate the theoretical predictions to current observations.
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References
Benz, A. O.: 1985, Solar Phys. 96, 357.
Benz, A. O.: 1986, Solar Phys. 104, 99.
Dröge, F.: 1967, Z. Astrophys. 66, 176.
Dröge, F.: 1977, Astron. Astrophys. 57, 285.
Dulk, G.: 1985, Ann. Rev. Astron. Astrophys. 23, 169.
Freund, H. P., Wong, H. K., Wu, C. S., and Xu, M. J.: 1983, Phys. Fluids 26, 2263.
Fung, P. C. W. and Yip, W. K.: 1966, Australian J. Phys. 19, 759.
Hewitt, R. G., Melrose, D. B., and Ronnmark, K. G.: 1982, Australian J. Phys. 35, 447.
Holman, G. D., Eichler, D., and Kundu, M. R.: 1980, in M. R. Kundu and T. Gergely (eds.), ‘Radio Physics of the Sun’, IAU Symp. 86.
Karimabadi, Menyuk, C. R., Sprangle, P., and Vlahos, L.: 1987, Astrophys. J. 316, 462.
Kovalev, V. A. and Korolev, O. S.: 1981, Soviet Astron. 25, 215.
Li, H. W.: 1987, Solar Phys. 111, 167 (this issue).
Lin, A. T., Chang, W. W., and Lin, C. C.: 1984, Phys. Fluids 27, 1054.
Mangeney, A. and Veltri, P.: 1976, Astron. Astrophys. 47, 165.
Melrose, D. B. 1980, Plasma Astrophysics, Gordon and Breach, New York.
Melrose, D. B. 1985, Solar Radiophysics, Cambridge Univ. Press, Cambridge.
Melrose, D. B. 1987, Solar Phys. 111, 89 (this issue).
Melrose, D. B. and Dulk, G. A.: 1982a, Astrophys. J. 259, 844.
Melrose, D. B. and Dulk, G. A.: 1982b, Astrophys. J. 259, L41.
Melrose, D. B. and Dulk, G. A.: 1984, Astrophys. J. 282, 308.
Omidi, N., Wu, C. S., and Gurnett, D. A.: 1984, J. Geoph. Res. 89, 883.
Pritchett, P. L.: 1984, Phys. Fluids 27, 2393.
Ramaty, R.: 1969, Astrophys. J. 178, 241.
Sharma, R. R. and Vlahos, L.: 1984, Astrophys. J. 280, 405.
Sharma, R. R., Vlahos, L., and Papadopoulos, K.: 1982, Astron. Astrophys. 112, 377.
Slottje, C.: 1978, Nature 275, 520.
Sprangle, P. and Vlahos, L.: 1983, Astrophys. J. 273, L95.
Sprangle, P. and Vlahos, L.: 1986, Phys. Rev. A33, 1261.
Stepanov: 1978, Soviet. Astrophys. Letters 4, 103.
Twiss, R. Q. and Roberts, J. A.: 1958, Australian J. Phys. 11, 424.
Vlahos, L. and Sharma, R. R.: 1985, Astrophys. J. 290, 347.
Vlahos, L. and Sprangle, P.: 1987, Astrophys. J. (in press).
Vlahos, L., Sharma, R. R., and Papadopoulos, K.: 1983, Astrophys. J. 275, 374.
Wagner, J. S., Lee, L. C., Wu, C. S., and Tajima: 1984, Radio Sci. 19, 509.
White, S. M., Melrose, D. B., and Dulk, G. A.: 1986, Astrophys. J. 308, 424.
Winglee, R. M.: 1985a, J. Geophys. Res. 90, 9663.
Winglee, R. M.: 1985b, Astrophys. J. 291, 160.
Wu, C. S.: 1985, Space Sci. Rev. 41, 215.
Wu, C. S. and Freund, H. P.: 1984, Radio Sci. 19, 519.
Wu, C. S., Tsai, S. T., Xu, M. J., and Shen, J. W.: 1981, Astrophys. J. 248, 384.
Zao, R. and Jin, S.: 1982, Sci. Sinica, Ser. A, 25, 422.
Zheleznyakov, V. V.: 1970, Radio Emission of the Sun and Planets, Pergamon Press, Oxford.
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Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.
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Vlahos, L. Electron cyclotron maser emission from solar flares. Sol Phys 111, 155–166 (1987). https://doi.org/10.1007/BF00145448
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DOI: https://doi.org/10.1007/BF00145448