Abstract
A number of authors claimed that radio sources above the neutral line of the magnetic field in solar active regions are due to non-thermal emission. This study shows that the thermal mechanism explains the radio emission from such sources. Models similar to those used for interpreting cyclotron lines were used in this study. Such models account for a steep decline in the spectrum at high frequencies and a low degree of polarization. The magnetic field between the two sunspots with an anti-parallel magnetic field has a lower gradient than the field above the sunspots. This, combined with the possibly high temperature in coronal loops connecting the sunspots, leads to the following conclusions. The optical thickness of the gyroresonance layers is increased and leads to more effective radiation at a harmonic number of 4 or 5. The lower gradient of the field between the sunspots also results in more rapid growth of emission intensity with increasing wavelength in this region than in the regions immediately above the sunspots. Additionally, the spatial averaging of the source structure due to the antenna beam pattern leads to a decrease in the degree of polarization in the region between the sunspots.
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References
Alissandrakis, C.E., Kundu, M.R.: 1982, Astrophys. J. Lett. 253, L49.
Alissandrakis, C.E., Gelfrejkh, G.B., Borovik, V.N., Korzhavin, A.N., Bogod, V.M., Nindos, A., Kundu, M.R.: 1993, Astron. Astrophys. 270, 509.
Akhmedov, S.B., Borovik, V.N., Gelfreikh, G.B., Bogod, V.M., Korzhavin, A.N., Petrov, Z.E., Dikij, V.N., Lang, K.R., Willson, R.F.: 1986, Astrophys. J. 301, 460.
Akhmedov, Sh.B., Bogod, V.M., Borovik, V.N., Gelfreikh, G.B, Korzhavin, A.N.: 1987, Solar maximum analysis. In: Stepanov, V.E., Obridko, V.N. (eds.) Proceedings of the International Workshop, VNU Science Press, Utrecht, 51.
Bogod, V.M., Yasnov, L.V.: 2009, Astrophys. Bull. 64, 372.
Bogod, V.M., Kaltman, T.I., Yasnov, L.V.: 2012, Astrophys. Bull. 67, 425.
Bogod, V.M., Stupishin, A.G., Yasnov, L.V.: 2012, Solar Phys. 276, 61.
Bogod, V.M., Gelfreikh, G.B., Wilson, R.F., Lang, K.R., Opeikina, L.V., Shatilov, V., Tsvetkov, S.V.: 1992, Solar Phys. 141, 303.
Borovik, V.N., Drake, N.A., Golovko, A.A.: 1989, In: Teplitskaya, R.B. (ed.) Solar Magnetic Fields and Corona, Proc. XIII Consultation Meeting on Solar Physics 2, Nauka, Siberian Division, Novosibirsk, 162.
Borovik, V.N., Vatrushin, S.M., Korzhavin, A.N.: 1989, Bull. Spec. Astrophys. Obs. 28, 123.
Borovik, V.N., Vatrushin, S.M., Korzhavin, A.N.: 1991, Bull. Spec. Astrophys. Obs. 28, 118.
Cheng, C.: 1977, Solar Phys. 55, 413.
Chiuderi Drago, F., Alissandrakis, C.E., Hagyard, M.: 1987, Solar Phys. 112, 89.
Gelfreikh, G.B.: 1985, In: Fomichev, V.V. (ed.) The Physics of the Solar Flares, Nauka, Moscow, 111.
Kaltman, T.I., Korzhavin, A.N., Peterova, N.G., Lubyshev, B.I., Maksimov, V.P., Alissandrakis, C.E., Fu, Q.: 1998, In: Alissandrakis, C., Schmieder, B. (eds.) Second Advances in Solar Physics Euroconference: Three-Dimensional Structure of Solar Active Regions, ASP Conf. Ser. 155, 140.
Kaltman, T.I., Bogod, V.M., Stupishin, A.G., Yasnov, L.V.: 2012, Astron. Rep. 56, 789.
Klimchuk, J.A.: 2000, Solar Phys. 193, 53.
Korzhavin, A.N., Vatrushin, S.M.: 1989, In: Somov, B.V., Fomichev, V.V. (eds.) The Physics of the Solar Plasma, Nauka, Moscow, 100.
Kundu, M.R., Alissandrakis, C.E.: 1984, Solar Phys. 94, 249.
Kundu, M.R., Velusamy, T.: 1980, Astrophys. J. Lett. 240, L63.
Kundu, M.R., Schmahl, E.J., Rao, A.P.: 1981, Astron. Astrophys. 94, 72.
Kundu, M.R., Alissandrakis, C.E., Bregman, J.D., Hin, A.C.: 1977, Astrophys. J. 213, 278.
Lee, J., White, S.M., Gopalswamy, N., Kundu, M.R.: 1997, Solar Phys. 174, 175.
Nagai, F.: 1980, Solar Phys. 68, 351.
Nita, G.M., Fleishman, G.D., Jing, J., Lesovoi, S.V., Bogod, V.M., Yasnov, L.V., Wang, H., Gary, D.E.: 2011, Astrophys. J. 737, 82.
Scherrer, P.H., Bogart, R.S., Bush, R.I., Hoeksema, J.T., Kosovichev, A.G., Schou, J., et al.: 1995, Solar Phys. 162, 129.
Schmahl, E.J., Shevgaonkar, R.K., Kundu, M.R., McConnell, D.: 1984, Solar Phys. 93, 305.
Selhorst, C.L., Silva-Válio, A., Costa, J.E.R.: 2008, Astron. Astrophys. 488, 1079.
Shibasaki, K., Alissandrakis, C.E., Pohjolainen, S.: 2011, Solar Phys. 273, 309.
Somov, B.V.: 1986, Astron. Astrophys. 163, 210.
Strong, K.T., Alissandrakis, C.E., Kundu, M.R.: 1984, Astrophys. J. 277, 865.
Sych, R.A., Uralov, A.M., Korzhavin, A.N.: 1993, Solar Phys. 144, 59.
Syrovatskii, S.I.: 1982, Solar Phys. 76, 3.
Uralov, A.M., Sych, R.A., Shchepkina, V.L., Zubkova, G.N., Smolkov, G.Ya.: 1998, Solar Phys. 183, 359.
Uralov, A.M., Nakajima, H., Zandanov, V.G., Grechnev, V.V.: 2000, Solar Phys. 197, 275.
Uralov, A.M., Grechnev, V.V., Rudenko, G.V., Rudenko, I.G., Nakajima, H.: 2008, Solar Phys. 249, 315.
Wiegelmann, T.: 2004, Solar Phys. 219, 87.
Willson, R.F.: 1983, Solar Phys. 89, 103.
Willson, R.F.: 1985, Astrophys. J. 298, 911.
Zheleznyakov, V.V.: 1997, Radiation in Astrophysical Plasmas, Yanus-K, Moscow, 528 (in Russian).
Zhelezniakov, V.V., Zlotnik, E.Ya.: 1980, In: Kundu, M.R., Gergely, T.E. (eds.) Radio Physics of the Sun, IAU Symp. 86, 87.
Zhelezniakov, V.V., Zlotnik, E.Ya.: 1989, Solar Phys. 121, 449.
Zirin, H., Feldman, U., Doschek, G.A., Kane, S.: 1981, Astrophys. J. 246, 321.
Zlotnik, E.Ya.: 1966, Astron. Zh. 45, 310 (in Russian).
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Yasnov, L.V. On the Nature of Neutral-Line-Associated Radio Sources. Sol Phys 289, 1215–1225 (2014). https://doi.org/10.1007/s11207-013-0396-3
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DOI: https://doi.org/10.1007/s11207-013-0396-3