Abstract
We have studied two microwave events with one-loop top (LT) and two-footpoint (FP) sources observed at 17 and 34 GHz by the Nobeyama Radioheliograph (NoRH). The microwave brightness peak is located near the FPs of the flare loop for one event, but near the LT for the other event. The microwave spectra of the FP sources are considerably softer (by Δα≈2.0) than that of the LT’s for both events. We assume that the microwave emission is gyro-synchrotron radiation from energetic electrons trapped in a magnetic dipole field and the energetic electron distribution is isotropic in pitch angle and power law. In the gyro-synchrotron calculations, the self-absorption and gyro-resonance absorption are taken into account simultaneously. The numerical calculations based on the general equation of radiative transfer show that the distributions of energetic electrons along a flare loop are highly inhomogeneous: accelerated electrons are concentrated in the FPs for both events. Even for the event with brightness maximum near the LT the electron number density of the LT source is still an order of magnitude lower than that of the FP sources. The emission peak near LT results mainly from the much harder spectral index of the energetic electrons in the LT source.
Similar content being viewed by others
References
Alissandrakis, C. E.: 1986, Solar Phys. 104, 207.
Alissandrakis, C. E. and Preka-Papadema, P.: 1984, Astron. Astrophys. 139, 507.
Alissandrakis, C. E., Nindos, A., and Kundu, M. R.: 1993, Solar Phys. 147, 343.
Bastian, T. S. and Kiplinger A.: 1991, in R. Winglee, and A. Kiplinger, (eds.), Max’91 Workshop 3: Max’91/SMM Solar Flare Observations and Theory, p. 153.
Bastian, T. S., Benz, A. O., and Gary, D. E.: 1998, ARA&A 36, 131.
Dulk, G. A. and Dennis, B. R.: 1982, Astrophys. J. 260, 875.
Holman, G. D., Kundu, M. R., and Papadopoulos, K.: 1982, Astrophys. J. 257, 354.
Klein, K. L. and Trottet, G.: 1984, Astron. Astrophys. 141, 67.
Kundu, M. R. and Vlahos, L.: 1982, Space Sci. Rev. 32, 403.
Kundu, M. R., Nindos, A., and Grechnev, V. V.: 2004, Astron. Astrophys. 420, 351.
Kundu, M. R., Nindos, A., White, S. M., and Grechnev, V. V.: 2001, Astrophys. J. 557, 880.
Melnikov, V. F., Shibasaki, K., and Reznikova, V. E.: 2002, Astrophys. J. 580, L185.
Melnikov, V. F., Reznikova, V. E., Yokoyama, T., and Shibasaki, K.: 2002, Proceedings of the 10th European Solar Physics Meeting, Solar Variability: From Core to Outer Frontiers, Prague, Czech Republic, 9–14 September, ESA SP, p. 506.
Marsh, K. A. and Hurford, G. J.: 1980, Astrophys. J. 240, L111.
Marsh, K. A., Hurford, G. J., Zirin, H., Dulk, G. A., Dennis, B. R., Frost, K. J., and Orwing, L. E.: 1981, Astrophys. J. 251, 797.
Nindos, A., White, S. M., Kundu, M. R., and Gary, D. E.: 2000, Astrophys. J. 533, 1053.
Nishio, M., Yaji, K., Kosugi, T., Nakajima, H., and Sakurai, T.: 1997, Astrophys. J. 486, 976.
Petrosian, V.: 1982, Astrophys. J. 255, L85.
Preka-Papadema, P. and Alissandrakis, C. E.: 1988, Astron. Astrophys. 191, 365.
Preka-Papadema, P. and Alissandrakis, C. E.: 1992, Astron. Astrophys. 257, 307.
Preka-Papadema, P., Alissandrakis, C. E., Dennis, B. R., and Kundu, M. R.: 1997, Solar Phys. 172, 233.
Ramaty, R.: 1969, Astrophys. J. 158, 753.
Shevgaonkar, R. K. and Kundu, M. R.: 1985, Astrophys. J. 292, 733.
Su, Y. N. and Huang, G. L.: 2004, Solar Phys. 219, 159.
Takakura, T.: 1972, Solar Phys. 26, 151.
Wang, H. M., Gary, D. E., Zirin, H., Kosugi, T., Schwartz, R. A., and Linford, G.: 1995, Astrophys. J. 444, L115.
Yokoyama, T., Nakajima, H., Shibasaki, K., Melnikov, V. F., and Stepanov, A. V.: 2002, Astrophys. J. 576, L187.
Zheleznyakov, V. V.: 1970, Radio Emission of The Sun and Planets, Pergamon Press, New York.
Zhou, A. H., Ma, C. Y., Zhang, J., Wang, X. D., and Zhang, H. Q.: 1998, Solar Phys. 177, 427.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Zhou, A.H., Su, Y.N. & Huang, G.L. Energetic Electrons in Loop Top and Footpoint Microwave Sources. Sol Phys 226, 327–336 (2005). https://doi.org/10.1007/s11207-005-7418-8
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s11207-005-7418-8