Origin of the Submillimeter Radio Emission During the Time-Extended Phase of a Solar Flare

  • G. Trottet
  • J.-P. Raulin
  • G. Giménez de Castro
  • T. Lüthi
  • A. Caspi
  • C. H. Mandrini
  • M. L. Luoni
  • P. Kaufmann


Solar flares observed in the 200 – 400 GHz radio domain may exhibit a slowly varying and time-extended component which follows a short (few minutes) impulsive phase and can last for a few tens of minutes to more than one hour. The few examples discussed in the literature indicate that such long-lasting submillimeter emission is most likely thermal bremsstrahlung. We present a detailed analysis of the time-extended phase of the 27 October 2003 (M6.7) flare, combining 1 – 345 GHz total-flux radio measurements with X-ray, EUV, and Hα observations. We find that the time-extended radio emission is, as expected, radiated by thermal bremsstrahlung. Up to 230 GHz, it is entirely produced in the corona by hot and cool materials at 7 – 16 MK and 1 – 3 MK, respectively. At 345 GHz, there is an additional contribution from chromospheric material at a few 104 K. These results, which may also apply to other millimeter–submillimeter radio events, are not consistent with the expectations from standard semiempirical models of the chromosphere and transition region during flares, which predict observable radio emission from the chromosphere at all frequencies where the corona is transparent.


Radio bursts, association with flares Radio bursts, microwave X-ray bursts, association with flares Flares, relation to magnetic field Chromosphere, active 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bagalá, L.G., Bauer, O.H., Fernández Borda, R., Francile, C., Haerendel, G., Rieger, R., Rovira, M.G.: 1999, The new Hα solar telescope at the German–Argentinian solar observatory. In: Wilson, A., et al. (eds.) Magnetic Fields and Solar Processes SP-448, ESA, Noordwijk, 469 – 474. Google Scholar
  2. Caspi, A.: 2010, Super-hot (T>30 MK) thermal plasma in solar flares. Ph.D. thesis, Department of Physics, University of California, Berkeley, CA 94720-7450, USA. Google Scholar
  3. Caspi, A., Lin, R.P.: 2010, RHESSI line and continuum observations of super-hot flare plasma. Astrophys. J. 725, L161 – L166. doi: 10.1088/2041-8205/725/2/L161. ADSCrossRefGoogle Scholar
  4. Chertok, I.M., Fomichev, V.V., Gorgutsa, R.V., Hildebrandt, J., Krüger, A., Magun, A., Zaitsev, V.V.: 1995, Solar radio bursts with a spectral flattening at millimeter wavelengths. Solar Phys. 160, 181 – 198. doi: 10.1007/BF00679104. ADSCrossRefGoogle Scholar
  5. Coyner, A.J., Alexander, D.: 2009, Implications of temporal development of localized ultraviolet and hard X-ray emission for large solar flares. Astrophys. J. 705, 554 – 567. doi: 10.1088/0004-637X/705/1/554. ADSCrossRefGoogle Scholar
  6. Dennis, B.R., Zarro, D.M.: 1993, The Neupert effect – What can it tell us about the impulsive and gradual phases of solar flares? Solar Phys. 146, 177 – 190. doi: 10.1007/BF00662178. ADSCrossRefGoogle Scholar
  7. Dere, K.P., Landi, E., Mason, H.E., Monsignori Fossi, B.C., Young, P.R.: 1997, CHIANTI – an atomic database for emission lines. Astron. Astrophys. Suppl. 125, 149 – 173. doi: 10.1051/aas:1997368. ADSCrossRefGoogle Scholar
  8. Dulk, G.A.: 1985, The solar atmosphere, solar magnetism and solar activity. In: McLean, D.J., Labrum, N.R. (eds.) Solar Radiophysics: Studies of Emission from the Sun at Metre Wavelengths (A87-13851 03-92), Cambridge University Press, Cambridge, 19 – 35. Google Scholar
  9. Elgarøy, E.Ø.: 1977, Solar Noise Storms, Pergamon, Oxford. Google Scholar
  10. Fernandez Borda, R.A., Mininni, P.D., Mandrini, C.H., Gómez, D.O., Bauer, O.H., Rovira, M.G.: 2002, Automatic solar flare detection using neural network techniques. Solar Phys. 206, 347 – 357. ADSCrossRefGoogle Scholar
  11. Fleishman, G.D., Kontar, E.P.: 2010, Sub-THz radiation mechanisms in solar flares. Astrophys. J. 709, L127 – L132. doi: 10.1088/2041-8205/709/2/L127. ADSCrossRefGoogle Scholar
  12. Fletcher, L., Hudson, H.: 2001, The magnetic structure and generation of EUV flare ribbons. Solar Phys. 204, 69 – 89. doi: 10.1023/A:1014275821318. ADSCrossRefGoogle Scholar
  13. Giménez de Castro, C.G., Trottet, G., Silva-Valio, A., Krucker, S., Costa, J.E.R., Kaufmann, P., Correia, E., Levato, H.: 2009, Submillimeter and X-ray observations of an X class flare. Astron. Astrophys. 507, 433 – 439. doi: 10.1051/0004-6361/200912028. ADSCrossRefGoogle Scholar
  14. Ginzburg, V.L., Syrovatskii, S.I.: 1965, Cosmic magnetobremsstrahlung (synchrotron radiation). Annu. Rev. Astron. Astrophys. 3, 297 – 346. doi: 10.1146/annurev.aa.03.090165.001501. ADSCrossRefGoogle Scholar
  15. Goff, C.P., van Driel-Gesztelyi, L., Démoulin, P., Culhane, J.L., Matthews, S.A., Harra, L.K., Mandrini, C.H., Klein, K.L., Kurokawa, H.: 2007, A multiple flare scenario where the classic long-duration flare was not the source of a CME. Solar Phys. 240, 283 – 299. doi: 10.1007/s11207-007-0260-4. ADSCrossRefGoogle Scholar
  16. Handy, B.N., Acton, L.W., Kankelborg, C.C., Wolfson, C.J., Akin, D.J., Bruner, M.E., Caravalho, R., Catura, R.C., Chevalier, R., Duncan, D.W., Edwards, C.G., Feinstein, C.N., Freeland, S.L., Friedlaender, F.M., Hoffmann, C.H., Hurlburt, N.E., Jurcevich, B.K., Katz, N.L., Kelly, G.A., Lemen, J.R., Levay, M., Lindgren, R.W., Mathur, D.P., Meyer, S.B., Morrison, S.J., Morrison, M.D., Nightingale, R.W., Pope, T.P., Rehse, R.A., Schrijver, C.J., Shine, R.A., Shing, L., Strong, K.T., Tarbell, T.D., Title, A.M., Torgerson, D.D., Golub, L., Bookbinder, J.A., Caldwell, D., Cheimets, P.N., Davis, W.N., Deluca, E.E., McMullen, R.A., Warren, H.P., Amato, D., Fisher, R., Maldonado, H., Parkinson, C.: 1999, The transition region and coronal explorer. Solar Phys. 187, 229 – 260. doi: 10.1023/A:1005166902804. ADSCrossRefGoogle Scholar
  17. Hurford, G.J., Schmahl, E.J., Schwartz, R.A., Conway, A.J., Aschwanden, M.J., Csillaghy, A., Dennis, B.R., Johns-Krull, C., Krucker, S., Lin, R.P., McTiernan, J., Metcalf, T.R., Sato, J., Smith, D.M.: 2002, The RHESSI imaging concept. Solar Phys. 210, 61 – 86. doi: 10.1023/A:1022436213688. ADSCrossRefGoogle Scholar
  18. Kaufmann, P., Raulin, J.P.: 2006, Can microbunch instability on solar flare accelerated electron beams account for bright broadband coherent synchrotron microwaves? Phys. Plasmas 13(7), 070701. doi: 10.1063/1.2244526. ADSCrossRefGoogle Scholar
  19. Kaufmann, P., Raulin, J., de Castro, C.G.G., Levato, H., Gary, D.E., Costa, J.E.R., Marun, A., Pereyra, P., Silva, A.V.R., Correia, E.: 2004, A new solar burst spectral component emitting only in the terahertz range. Astrophys. J. 603, L121 – L124. doi: 10.1086/383186. ADSCrossRefGoogle Scholar
  20. Kaufmann, P., Levato, H., Cassiano, M.M., Correia, E., Costa, J.E.R., Giménez de Castro, C.G., Godoy, R., Kingsley, R.K., Kingsley, J.S., Kudaka, A.S., Marcon, R., Martin, R., Marun, A., Melo, A.M., Pereyra, P., Raulin, J., Rose, T., Silva Valio, A., Walber, A., Wallace, P., Yakubovich, A., Zakia, M.B.: 2008, New telescopes for ground-based solar observations at submillimeter and mid-infrared. Proc. SPIE 7012, 70120L. doi: 10.1117/12.788889. ADSCrossRefGoogle Scholar
  21. Kaufmann, P., Trottet, G., Giménez de Castro, C.G., Raulin, J., Krucker, S., Shih, A.Y., Levato, H.: 2009, Sub-terahertz, microwaves and high energy emissions during the 6 December 2006 flare, at 18:40 UT. Solar Phys. 255, 131 – 142. doi: 10.1007/s11207-008-9312-7. ADSCrossRefGoogle Scholar
  22. Klein, K.L., Trottet, G., Samwel, S., Malandraki, O.: 2011, Particle acceleration and propagation in strong flares without major solar energetic particle events. Solar Phys. 269, 309 – 333. doi: 10.1007/s11207-011-9710-0. ADSCrossRefGoogle Scholar
  23. Kundu, M.R., White, S.M., Gopalswamy, N., Lim, J.: 1994, Millimeter, microwave, hard X-ray, and soft X-ray observations of energetic electron populations in solar flares. Astrophys. J. Suppl. 90, 599 – 610. doi: 10.1086/191881. ADSCrossRefGoogle Scholar
  24. Lin, R.P., Dennis, B.R., Hurford, G.J., Smith, D.M., Zehnder, A., Harvey, P.R., Curtis, D.W., Pankow, D., Turin, P., Bester, M., Csillaghy, A., Lewis, M., Madden, N., van Beek, H.F., Appleby, M., Raudorf, T., McTiernan, J., Ramaty, R., Schmahl, E., Schwartz, R., Krucker, S., Abiad, R., Quinn, T., Berg, P., Hashii, M., Sterling, R., Jackson, R., Pratt, R., Campbell, R.D., Malone, D., Landis, D., Barrington-Leigh, C.P., Slassi-Sennou, S., Cork, C., Clark, D., Amato, D., Orwig, L., Boyle, R., Banks, I.S., Shirey, K., Tolbert, A.K., Zarro, D., Snow, F., Thomsen, K., Henneck, R., McHedlishvili, A., Ming, P., Fivian, M., Jordan, J., Wanner, R., Crubb, J., Preble, J., Matranga, M., Benz, A., Hudson, H., Canfield, R.C., Holman, G.D., Crannell, C., Kosugi, T., Emslie, A.G., Vilmer, N., Brown, J.C., Johns-Krull, C., Aschwanden, M., Metcalf, T., Conway, A.: 2002, The Reuven Ramaty high-energy solar spectroscopic imager (RHESSI). Solar Phys. 210, 3 – 32. doi: 10.1023/A:1022428818870. ADSCrossRefGoogle Scholar
  25. Luoni, M.L., Mandrini, C.H., Cristiani, G.D., Démoulin, P.: 2007, The magnetic field topology associated with two M flares. Adv. Space Res. 39, 1382 – 1388. doi: 10.1016/j.asr.2007.02.005. ADSCrossRefGoogle Scholar
  26. Lüthi, T., Lüdi, A., Magun, A.: 2004, Determination of the location and effective angular size of solar flares with a 210 GHz multibeam radiometer. Astron. Astrophys. 420, 361 – 370. doi: 10.1051/0004-6361:20035899. ADSCrossRefGoogle Scholar
  27. Lüthi, T., Magun, A., Miller, M.: 2004, First observation of a solar X-class flare in the submillimeter range with KOSMA. Astron. Astrophys. 415, 1123 – 1132. doi: 10.1051/0004-6361:20034624. ADSCrossRefGoogle Scholar
  28. Machado, M.E., Avrett, E.H., Vernazza, J.E., Noyes, R.W.: 1980, Semiempirical models of chromospheric flare regions. Astrophys. J. 242, 336 – 351. doi: 10.1086/158467. ADSCrossRefGoogle Scholar
  29. Mandrini, C.H., Démoulin, P., Schmieder, B., Deluca, E.E., Pariat, E., Uddin, W.: 2006, Companion event and precursor of the X17 flare on 28 October 2003. Solar Phys. 238, 293 – 312. doi: 10.1007/s11207-006-0205-3. ADSCrossRefGoogle Scholar
  30. Mauas, P.J.D., Machado, M.E., Avrett, E.H.: 1990, The white-light flare of 1982 June 15 – Models. Astrophys. J. 360, 715 – 726. doi: 10.1086/169157. ADSCrossRefGoogle Scholar
  31. Mazzotta, P., Mazzitelli, G., Colafrancesco, S., Vittorio, N.: 1998, Ionization balance for optically thin plasmas: Rate coefficients for all atoms and ions of the elements H to NI. Astron. Astrophys. Suppl. 133, 403 – 409. doi: 10.1051/aas:1998330. ADSCrossRefGoogle Scholar
  32. Melo, A.M., Kaufmann, P., Giménez de Castro, C.G., Raulin, J.P., Levato, H., Marun, A., Giuliani, J.L., Pereyra, P.: 2005, Submillimeter-wave atmospheric transmission at El Leoncito, Argentina Andes. IEEE Trans. Antennas Propag. 53, 1528 – 1534. doi: 10.1109/TAP.2005.844435. ADSCrossRefGoogle Scholar
  33. Neupert, W.M.: 1968, Comparison of solar X-ray line emission with microwave emission during flares. Astrophys. J. 153, L59 – L64. doi: 10.1086/180220. ADSCrossRefGoogle Scholar
  34. Pohjolainen, S., Valtaoja, E., Urpo, S.: 1996, Solar microwave burst emission relation to X-ray radiation. Astron. Astrophys. 314, 947 – 956. ADSGoogle Scholar
  35. Raulin, J.P., Makhmutov, V.S., Kaufmann, P., Pacini, A.A., Lüthi, T., Hudson, H.S., Gary, D.E.: 2004, Analysis of the impulsive phase of a solar flare at submillimeter wavelengths. Solar Phys. 223, 181 – 199. doi: 10.1007/s11207-004-1300-y. ADSCrossRefGoogle Scholar
  36. Raulin, J., White, S.M., Kundu, M.R., Silva, A.V.R., Shibasaki, K.: 1999, Multiple components in the millimeter emission of a solar flare. Astrophys. J. 522, 547 – 558. doi: 10.1086/322974. ADSCrossRefGoogle Scholar
  37. Silva, A.V.R., Share, G.H., Murphy, R.J., Costa, J.E.R., de Castro, C.G.G., Raulin, J., Kaufmann, P.: 2007, Evidence that synchrotron emission from nonthermal electrons produces the increasing submillimeter spectral component in solar flares. Solar Phys. 245, 311 – 326. doi: 10.1007/s11207-007-9044-0. ADSCrossRefGoogle Scholar
  38. Smith, D.M., Lin, R.P., Turin, P., Curtis, D.W., Primbsch, J.H., Campbell, R.D., Abiad, R., Schroeder, P., Cork, C.P., Hull, E.L., Landis, D.A., Madden, N.W., Malone, D., Pehl, R.H., Raudorf, T., Sangsingkeow, P., Boyle, R., Banks, I.S., Shirey, K., Schwartz, R.: 2002, The RHESSI spectrometer. Solar Phys. 210, 33 – 60. doi: 10.1023/A:1022400716414. ADSCrossRefGoogle Scholar
  39. Thomas, R.J., Crannell, C.J., Starr, R.: 1985, Expressions to determine temperatures and emission measures for solar X-ray events from GOES measurements. Solar Phys. 95, 323 – 329. doi: 10.1007/BF00152409. ADSCrossRefGoogle Scholar
  40. Trottet, G., Krucker, S., Lüthi, T., Magun, A.: 2008, Radio submillimeter and γ-ray observations of the 2003 October 28 solar flare. Astrophys. J. 678, 509 – 514. doi: 10.1086/528787. ADSCrossRefGoogle Scholar
  41. Trottet, G., Raulin, J., Kaufmann, P., Siarkowski, M., Klein, K., Gary, D.E.: 2002, First detection of the impulsive and extended phases of a solar radio burst above 200 GHz. Astron. Astrophys. 381, 694 – 702. doi: 10.1051/0004-6361:20011556. ADSCrossRefGoogle Scholar
  42. White, S.M., Kundu, M.R.: 1992, Solar observations with a millimeter-wavelength array. Solar Phys. 141, 347 – 369. doi: 10.1007/BF00155185. ADSCrossRefGoogle Scholar
  43. White, S.M., Thomas, R.J., Schwartz, R.A.: 2005, Updated expressions for determining temperatures and emission measures from GOES soft X-ray measurements. Solar Phys. 227, 231 – 248. doi: 10.1007/s11207-005-2445-z. ADSCrossRefGoogle Scholar
  44. Young, P.R., Landi, E., Thomas, R.J.: 1998, CHIANTI: an atomic database for emission lines. II. Comparison with the SERTS-89 active region spectrum. Astron. Astrophys. 329, 291 – 314. ADSGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • G. Trottet
    • 1
    • 2
  • J.-P. Raulin
    • 2
  • G. Giménez de Castro
    • 2
  • T. Lüthi
    • 3
  • A. Caspi
    • 4
  • C. H. Mandrini
    • 5
    • 6
  • M. L. Luoni
    • 5
  • P. Kaufmann
    • 2
    • 7
  1. 1.Observatoire de Paris, LESIA-CNRS UMR 8109Univ. P & M Curie and Paris-Diderot, Observatoire de MeudonMeudonFrance
  2. 2.CRAAM Universidade Presbiteriana MackenzieSão PauloBrazil
  3. 3.Hexagon MetrologyLeica Geosystem AGUnterenfeldenSwitzerland
  4. 4.Space Sciences LaboratoryUniversity of CaliforniaBerkeleyUSA
  5. 5.Instituto de Astronomía y Física del EspacioCONICET-UBABuenos AiresArgentina
  6. 6.Facultad de Ciencias Exactas y NaturalesFCEN-UBABuenos AiresArgentina
  7. 7.Centro de Componentes SemicondutoresUniversidade Estadual de CampinasCampinasBrazil

Personalised recommendations