Advertisement

Solar Physics

, Volume 245, Issue 2, pp 311–326 | Cite as

Evidence that Synchrotron Emission from Nonthermal Electrons Produces the Increasing Submillimeter Spectral Component in Solar Flares

  • Adriana V. R. Silva
  • G. H. Share
  • R. J. Murphy
  • J. E. R. Costa
  • C. G. Giménez de Castro
  • J.-P. Raulin
  • P. Kaufmann
Article

Abstract

We investigate the origin of the increasing spectra observed at submillimeter wavelengths detected in the flare on 2 November 2003 starting at 17:17 UT. This flare, classified as an X8.3 and 2B event, was simultaneously detected by RHESSI and the Solar Submillimeter Telescope (SST) at 212 and 405 GHz. Comparison of the time profiles at various wavelengths shows that the submillimeter emission resembles that of the high-energy X rays observed by RHESSI whereas the microwaves observed by the Owens Valley Solar Array (OVSA) resemble that of ∼50 keV X rays. Moreover, the centroid position of the submillimeter radiation is seen to originate within the same flaring loops of the ultraviolet and X-ray sources. Nevertheless, the submillimeter spectra are distinct from the usual microwave spectra, appearing to be a distinct spectral component with peak frequency in the THz range. Three possibilities to explain this increasing radio spectra are discussed: (1) gyrosynchrotron radiation from accelerated electrons, (2) bremsstrahlung from thermal electrons, and (3) gyrosynchrotron emission from the positrons produced by pion or radioactive decay after nuclear interactions. The latter possibility is ruled out on the grounds that to explain the submillimeter observations requires 3000 to 2×105 more positrons than what is inferred from X-ray and γ-ray observations. It is possible to model the emission as thermal; however, such sources would produce too much flux in the ultraviolet and soft X-ray wavelengths. Nevertheless we are able to explain both spectral components at microwave and submillimeter wavelengths by gyrosynchrotron emission from the same population of accelerated electrons that emit hard X rays and γ rays. We find that the same 5×1035 electrons inferred from RHESSI observations are responsible for the compact submillimeter source (0.5 arcsec in radius) in a region of 4500 G low in the atmosphere, and for the traditional microwave spectral component by a more extended source (50 arcsec) in a 480 G magnetic field located higher up in the loops. The extreme values in magnetic field and source size required to account for the submillimeter emission can be relaxed if anisotropy and transport of the electrons are taken into account.

Keywords

Sun: solar flares Sun: synchrotron radiation Sun: positrons 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Costa, J.E.R., Correia, E., Kaufmann, P., Magun, A., Herrmann, R.: 1995, Solar Phys. 159, 157. CrossRefADSGoogle Scholar
  2. Dulk, G.A.: 1985, Ann. Rev. Astron. Astrophys. 23, 169. CrossRefADSGoogle Scholar
  3. Fleishman, G.D., Melnikov, V.F.: 2003, Astrophys. J. 587, 823. CrossRefADSGoogle Scholar
  4. Frost, K.J., Dennis, B.R.: 1971, Astrophys. J. 165, 655. CrossRefADSGoogle Scholar
  5. Giménez de Castro, C.G., Raulin, J.-P., Makhmutov, V.S., Kaufmann, P., Costa, J.E.R.: 1999, Astron. Astrophys. Suppl. Ser. 140, 373. CrossRefADSGoogle Scholar
  6. Holman, G.D.: 2003, Astrophys. J. 586, 606. CrossRefADSGoogle Scholar
  7. Hurford, G.J., Krucker, S., Lin, R.P., Schwartz, R.A., Share, F.H., Smith, D.M.: 2006, Astrophys. J. 644, L93. CrossRefADSGoogle Scholar
  8. Kaufmann, P., Raulin, J.: 2006, Phys. Plasma 13, 070701. CrossRefGoogle Scholar
  9. Kaufmann, P., Correia, E., Costa, J.E.R., Zodi Vaz, A.M.: 1986, Astron. Astrophys. 157, 11. ADSGoogle Scholar
  10. Kaufmann, P., Costa, J.E.R., Giménez de Castro, C.G., Hadano, Y.R., Kingsley, J.S., Kingsley, R.K., et al.: 2001, In: Pinho, J.J., Cavalcante, G.P.S., Oliveira, A.H. (eds.) Proc. 2001 SBMO/IEEE MTT-S International Microwave and Optoeletronics Conference, 439. Google Scholar
  11. Kaufmann, P., Raulin, J.-P., Melo, A.M., Correia, E., Costa, J.E.R., Giménez de Castro, C.G., et al.: 2002, Astrophys. J. 574, 1059. CrossRefADSGoogle Scholar
  12. Kaufmann, P., Raulin, J.-P., Giménez de Castro, C.G., Levato, H., Gary, D.E., Costa, J.E.R., et al.: 2004, Astrophys. J. 603, L121. CrossRefADSGoogle Scholar
  13. 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
  14. Livingston, W., Harvey, J.W., Malanushenko, O.V., Webster, L.: 2006, Solar Phys. 239, 41. CrossRefADSGoogle Scholar
  15. Lüthi, T., Lüdi, A., Magun, A.: 2004, Astron. Astrophys. 420, 361. CrossRefADSGoogle Scholar
  16. Lüthi, T., Magun, A., Miller, M.: 2004, Astron. Astrophys. 415, 1123. CrossRefADSGoogle Scholar
  17. Murphy, R.J., Dermer, C.D., Ramaty, R.: 1987, Astrophys. J. Suppl. Ser. 63, 721. CrossRefADSGoogle Scholar
  18. Ohki, K., Hudson, H.S.: 1975, Solar Phys. 43, 405. CrossRefADSGoogle Scholar
  19. Ramaty, R.: 1969, Astrophys. J. 158, 753. CrossRefADSGoogle Scholar
  20. Ramaty, R., Schwartz, R.A., Enome, S., Nakajima, H.: 1994, Astrophys. J. 436, 941. CrossRefADSGoogle Scholar
  21. Raulin, J.-P., White, S.M., Kundu, M.R., Silva, A.V.R., Shibasaki, K.: 1999, Astrophys. J. 522, 547. CrossRefADSGoogle Scholar
  22. Raulin, J.-P., Kaufmann, P., Giménez de Castro, C.G., Pacini, A.A., Makhmutov, V.S., Levato, H., et al.: 2003, Astrophys. J. 592, 580. CrossRefADSGoogle Scholar
  23. Raulin, J.P., Makhmutov, V.S., Kaufmann, P., Pacini, A.A., Lüthi, T., Hudson, H.S., et al.: 2004, Solar Phys. 223, 181. CrossRefADSGoogle Scholar
  24. Raymond, J.C., Holman, G., Ciaravella, A., Panasyuk, A., Ko, Y.-K., Kohl, J.: 2007, Astrophys. J. 659, 750. CrossRefADSGoogle Scholar
  25. Sakai, J.I., Nagasugi, Y.: 2007, Astron. Astrophys. 470, 1117. CrossRefADSGoogle Scholar
  26. Sakai, J.I., Nagasugi, Y., Saito, S., Kaufmann, P.: 2006, Astron. Astrophys. 457, 313. CrossRefADSGoogle Scholar
  27. Share, G.H., Murphy, R.J., Smith, D.M., Schwartz, R.A., Lin, R.P.: 2004, Astrophys. J. 615, L169. CrossRefADSGoogle Scholar
  28. Silva, A.V.R., Laganá, T.F., Giménez de Castro, C.G., Kaufmann, P., Costa, J.E.R., Levato, H., et al.: 2005, Solar Phys. 227, 265. CrossRefADSGoogle Scholar
  29. Silva, A.V.R., Valente, M.M.: 2002, Solar Phys. 206, 177. CrossRefADSGoogle Scholar
  30. Simões, P.J.A., Costa, J.E.R.: 2006, Astron. Astrophys. 453, 729. CrossRefADSGoogle Scholar
  31. Stein, W.A., Ney, E.P.: 1963, J. Geophys. Res. 68, 65. ADSGoogle Scholar
  32. Thomas, R.J., Crannell, C.J., Starr, R.: 1985, Solar Phys. 95, 323. CrossRefADSGoogle Scholar
  33. Trottet, G.: 2006, In: Fang, C., Schmieder, B., Ding, N.U.P. (eds.), Third French – Chinese Meeting on Solar Physics, 82. Google Scholar
  34. Trottet, G., Raulin, J.-P., Kaufmann, P., Siarkowski, M., Klein, K.-L., Gary, D.E.: 2002, Astron. Astrophys. 381, 694. CrossRefADSGoogle Scholar
  35. Trottet, G., Lüthi, T., Myagkova, I.N., Dauphin, C., Magun, A., Vilmer, N., et al.: 2004, In: 35th COSPAR Scientific Assembly, 2234. Google Scholar
  36. Vestrand, W.T., Forrest, D.J., Chupp, E.L., Rieger, E., Share, G.H.: 1987, Astrophys. J. 322, 1010. CrossRefADSGoogle Scholar
  37. Vilmer, N., Trotter, G., Kane, S.R.: 1982, Astron. Astrophys. 108, 306. ADSGoogle Scholar
  38. White, S.M., Krucker, S., Shibasaki, K., Yokoyama, T., Shimojo, M., Kundu, M.R.: 2003, Astrophys. J. 595, L111. CrossRefADSGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Adriana V. R. Silva
    • 1
  • G. H. Share
    • 2
    • 3
  • R. J. Murphy
    • 3
  • J. E. R. Costa
    • 4
  • C. G. Giménez de Castro
    • 1
  • J.-P. Raulin
    • 1
  • P. Kaufmann
    • 1
    • 5
  1. 1.CRAAMUniversidade Presbiteriana MackenzieSão PauloBrazil
  2. 2.Department of AstronomyUniversity of MarylandCollege ParkUSA
  3. 3.E. O. Hulburt Center for Space Research, Code 7652Naval Research LaboratoryWashingtonUSA
  4. 4.DAS, INPESão José dos CamposBrazil
  5. 5.CCSUniversidade Estadual de CampinasCampinasBrazil

Personalised recommendations