Solar Physics

, Volume 257, Issue 2, pp 335–350 | Cite as

Spatial and Spectral Behaviors of Solar Flares Observed in Microwaves

  • Zongjun Ning
  • Wenda Cao


The spatial and spectral behaviors of two solar flares observed by the Nobeyama Radioheliograph (NoRH) on 24 August 2002 and 22 August 2005 are explored. They were observed with a single loop-top source and double footpoint sources at the beginning, then with looplike structures for the rest of the event. NoRH has high spatial and temporal resolution at the two frequencies of 17 and 34 GHz where a nonthermal radio source is often optically thin. Such capabilities give us an opportunity to study the spatial and spectral behaviors of different microwave sources. The 24 August 2002 flare displayed a soft – hard – soft (SHS) spectral pattern in the rising – peak – decay phases at 34 GHz, which was also observed for the spectral behavior of both loop-top and footpoint sources. In contrast, the 22 August 2005 flare showed a soft – hard – harder (SHH) spectral pattern for its both loop-top and footpoint sources. It is interesting that this event showed a harder spectrum in the early rising phase. We found a positive correlation between the spectral index and microwave flux in both the loop-top source and the footpoint sources in both events. The conclusions drawn from the flux index could apply to the electron index as well, because of their simple linear relationship under the assumption of nonthermal gyrosynchrotron mechanism. Such a property of spatial and spectral behaviors of microwave sources gives an observational constraint on the electron acceleration mechanism and electron propagation.


Flares Radio radiation 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Aschwanden, M.J.: 1998, In: Watanabe, T., Kosugi, T., Sterling, A.C. (eds.) Observational Plasma Astrophysics: Five Years of YOHKOH and Beyond, Kluwer Academic, Boston, 285. Google Scholar
  2. Aschwanden, M.J., Benz, A.O., Kane, S.R.: 1990, Astron. Astrophys. 229, 206. ADSGoogle Scholar
  3. Alexander, D., Metcalf, T.R.: 1997, Astrophys. J. 489, 442. CrossRefADSGoogle Scholar
  4. Bastian, T.S., Benz, A.O., Gary, D.E.: 1998, Annu. Rev. Astron. Astrophys. 36, 131. CrossRefADSGoogle Scholar
  5. Battaglia, M., Benz, A.O.: 2006, Astron. Astrophys. 456, 751. CrossRefADSGoogle Scholar
  6. Battaglia, M., Benz, A.O.: 2007, Astron. Astrophys. 466, 713. CrossRefADSGoogle Scholar
  7. Castelli, J.P., Guidice, D.A.: 1976, Vistas Astron. 19, 355. CrossRefADSGoogle Scholar
  8. Dennis, B.R.: 1985, Solar Phys. 100, 465. CrossRefADSGoogle Scholar
  9. Dennis, B.R., Frost, K.J., Orwig, L.E.: 1981, Astrophys. J. 244, L167. CrossRefADSGoogle Scholar
  10. Dulk, G.A., Marsh, K.A.: 1982, Astrophys. J. 259, 350. CrossRefADSGoogle Scholar
  11. Grigis, P.C., Benz, A.O.: 2004, Astron. Astrophys. 426, 1093. CrossRefADSGoogle Scholar
  12. Hanaoka, Y.: 1996, Solar Phys. 165, 275. CrossRefADSGoogle Scholar
  13. Hanaoka, Y.: 1999, Publ. Astron. Soc. Japan 51, 483. ADSGoogle Scholar
  14. Hoyng, P., Duijveman, A., Machado, M.E., Rust, D.M., Svestka, Z., Boelee, A., de Jager, et al.: 1981, Astrophys. J. 246, L155. CrossRefADSGoogle Scholar
  15. Kane, S.R., Anderson, K.A.: 1970, Astrophys. J. 162, 1003. CrossRefADSGoogle Scholar
  16. Karlický, M.: 2004, New Astron. 9, 383. CrossRefADSGoogle Scholar
  17. Kawabata, K., Ogawa, H., Takakura, T., Tsuneta, S., Ohki, K., Yoshimori, M., Okudaira, K., Hirasima, Y., Kondo, I.: 1982, Hinotori Symposium on Solar Flares, Univ. Tokyo, 168. Google Scholar
  18. Kosugi, T., Dennis, B.R., Kai, K.: 1988, Astrophys. J. 324, 1118. CrossRefADSGoogle Scholar
  19. Kundu, M.R., Schmahl, E.J., Velusamy, T.: 1982, Astrophys. J. 253, 963. CrossRefADSGoogle Scholar
  20. Kundu, M.R., Nitta, N., White, S.M., Shibasaki, K., Enome, S., Sakao, T., Kosugi, T., Sakurai, T.: 1995, Astrophys. J. 454, 522. CrossRefADSGoogle Scholar
  21. Li, Y.P., Gan, W.Q.: 2005, Astrophys. J. 629, L137. CrossRefADSGoogle Scholar
  22. Lin, R.P., Dennis, B.R., Hurford, G.J., Smith, D.M., Zehnder, A., Harvey, P.R., et al.: 2002, Solar Phys. 210, 3. CrossRefADSGoogle Scholar
  23. Liu, W., Liu, S., Jiang, Y.W., Petrosian, V.: 2006, Astrophys. J. 649, 1124. CrossRefADSGoogle Scholar
  24. Marsh, K.A., Hurford, G.J.: 1980, Astrophys. J. 240, L111. CrossRefADSGoogle Scholar
  25. Masuda, S., Kosugi, T., Hara, H., Tsuneta, S., Ogawara, Y.: 1994, Nature 371, 495. CrossRefADSGoogle Scholar
  26. Melnikov, V.F.: 2006, Solar Physics with the Nobeyama Radioheliograph, Nobeyama Solar Radio Observatory, 11. Google Scholar
  27. Melnikov, V.F., Magun, A.: 1998, Solar Phys. 178, 153. CrossRefADSGoogle Scholar
  28. Melnikov, V.F., Silva, A.V.R.: 2000, In: Ramaty, R., Mandzhavidze, N. (eds.) High Energy Solar Physics Workshop – Anticipating Hessi SP-506, Astron. Soc. Pac., San Francisco, 371. Google Scholar
  29. Melnikov, V.F., Shibasaki, K., Reznikova, V.E.: 2002, Astrophys. J. 580, L185. CrossRefADSGoogle Scholar
  30. Melnikov, V.F., Reznikova, V.E., Yokoyama, T., Shibasaki, K.: 2002, In: Wilson, A. (ed.) Solar Variability: From Core to Outer Frontiers SP-506, ESA, Noordwijk, 339. Google Scholar
  31. Nakajima, H.: 1983, Solar Phys. 86, 427. CrossRefADSGoogle Scholar
  32. Nakajima, H., Sekiguchi, H., Sawa, M., Kai, K., Kawashima, S.: 1985, Publ. Astron. Soc. Japan 37, 163. ADSGoogle Scholar
  33. Ning, Z.: 2007a, Astrophys. J. 659, L69. CrossRefADSGoogle Scholar
  34. Ning, Z.: 2007b, Astrophys. J. 671, L197. CrossRefADSGoogle Scholar
  35. Ning, Z.: 2008, Solar Phys. 247, 53. CrossRefADSGoogle Scholar
  36. Ning, Z., Ding, M.: 2007, Publ. Astron. Soc. Japan 59, 373. ADSGoogle Scholar
  37. Nishio, M., Yaji, K., Kosugi, T., Nakajima, H., Sakurai, T.: 1997, Astrophys. J. 489, 976. CrossRefADSGoogle Scholar
  38. Nita, G.M., Gary, D.E., Lee, J.: 2004, Astrophys. J. 605, 528. CrossRefADSGoogle Scholar
  39. Parks, G.K., Winckler, J.R.: 1969, Astrophys. J. 155, L117. CrossRefADSGoogle Scholar
  40. Petrosian, V., Donaghy, T.Q., McTiernan, J.M.: 2002, Astrophys. J. 569, 459. CrossRefADSGoogle Scholar
  41. Saint-Hilaire, P., Krucker, S., Lin, R.P.: 2008, Solar Phys. 250, 53. CrossRefADSGoogle Scholar
  42. Sakao, T.: 1994, Ph.D. Thesis, Univ. Tokyo. Google Scholar
  43. Scherrer, P.H., Bogart, R.S., Bush, R.I., Hoeksema, J.T., Kosovichev, A.G., Schou, J., et al.: 1995, Solar Phys. 162, 129. CrossRefADSGoogle Scholar
  44. Su, Y.N., Huang, G.L.: 2004, Solar Phys. 219, 159. CrossRefADSGoogle Scholar
  45. Sui, L., Holman, G.D., Dennis, B.R.: 2004, Astrophys. J. 612, 546. CrossRefADSGoogle Scholar
  46. Sui, L., Holman, G.D., White, S.M., Zhang, J.: 2005, Astrophys. J. 633, 1175. CrossRefADSGoogle Scholar
  47. Wang, H., Gary, D.E., Zirin, H., Schwartz, R.A., Sakao, T., Kosugi, T., Shibata, K.: 1995, Astrophys. J. 453, 505. CrossRefADSGoogle Scholar
  48. Yokoyama, T., Nakajima, H., Shibasaki, K., Melnikov, V.F., Stepanov, A.V.: 2002, Astrophys. J. 576, L87. CrossRefADSGoogle Scholar
  49. Zhou, A.H., Su, Y.N., Huang, G.L.: 2005, Solar Phys. 226, 327. CrossRefADSGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Purple Mountain ObservatoryNanjingPeople’s Republic of China
  2. 2.Center for Solar Terrestrial ResearchNew Jersey Institute of TechnologyNewarkUSA

Personalised recommendations