The Role of Quasi-Transverse Propagation in Observed Polarization of Flare Loop Microwave Radiation
Tóm tắt
The ordinary mode of gyrosynchrotron radiation was identified to be predominant in some segments of flare loops in solar flares of July 19, 2012, and October 22, 2014. These events were studied by investigation of the quasi-transverse propagation effect on the observed polarization. The analysis involved reconstruction of the magnetic field topology at the linear force-free approximation based on the data of the SDO HMI space telescope and the subsequent simulation of radio emission of flare loops with the GX Simulator software package. The quasi-transverse propagation effect was established to be characteristic for both events, but its influence on the radio emission polarization at a frequency of 17 GHz was observed only in the October 22, 2014 flare.
Tài liệu tham khảo
Alissandrakis, C.E. and Preka-Papadema, P., Microwave emission and polarization of a flaring loop, Astron. Astrophys., 1984, vol. 139, no. 2, pp. 507–511.
Bogod, V.M., Gelfreikh, G.B., Ryabov, B.I., and Hafizov, S.R., Coronal magnetic fields from the effect of the double inversion of circular polarization of radio emission, Astron. Soc. Pac. Conf. Ser., 1993, vol. 46, pp. 302–305.
Cohen, M.H., Magnetoionic mode coupling at high frequencies, Astrophys. J., 1960, vol. 131, pp. 664–679.
Cohen, M.H., Microwave polarization and coronal magnetic fields, Astrophys. J., 1961, vol. 133, pp. 978–981.
Cohen, M.H. and Dwarkin, M.J., Perpendicular intersections with a dipole field, J. Geophys. Res., 1961, vol. 66, no. 2, pp. 411–419.
Kuznetsov, A.A., Nita, G.M., and Fleishman, G.D., Three-dimensional simulations of gyrosynchrotron emission from mildly anisotropic nonuniform electron distributions in symmetric magnetic loops, Astrophys. J., 2011, vol. 742, no. 2, id 87.
Morgachev, A.S., Kuznetsov, S.A., Melnikov, V.F., and Simões, J.A., Modeling the distribution of circular polarization degree of microwave emission along the flare loops in event July 19, 2012, Geomagn. Aeron. (Engl. Transl.), 2015, vol. 55, no. 8, pp. 1118–1123.
Morgachev, A.S., Melnikov, V.F., and Kuznetsov, S.A., Search for accelerated electron anisotropy signatures based on observed polarization of the flaring loop microwave emission, Geomagn. Aeron. (Engl. Transl.), 2016, vol. 56, no. 8, pp. 1045–1051.
Nita, G.M., Fleishman, G.D., Kuznetsov, A.A., Kontar, E.P., and Gary, D.E., Three-dimensional radio and X-ray modeling and data analysis software: Revealing flare complexity, Astrophys. J., 2015, vol. 799, no. 2, id 236.
Peterova, N.G., and Akhmedov, Sh.B., On the influence of transversal magnetic fields on the polarized radio radiation of local sources on the Sun, Astron. Zh., 1973, vol. 50, pp. 1220–1232.
Ryabov, B.I., Coronal magnetic field measurements through quasi-transverse propagation, in Solar and Space Weather Radiophysics, Gary, D.E. and Keller, C.U., Eds., Dordrecht: Springer, 2004, vol. 314, ch. 7, pp. 135–152.
Ryabov, B.I., Pilyeva, N.A., Alissandrakis, C.E., Shibasaki, K., Bogod, V.M., Garaimov, V.I., and Gelfreikh, G.B., Coronal magnetography of an active region from microwave polarization inversion, Sol. Phys., 1999, vol. 185, no. 1, pp. 157–175.
Selhorst, C.L., Costa, J.E.R., and Silva, A.V.R., 3-D solar atmospheric model over active regions, in Proceedings of the 11th European Solar Physics Meeting “The Dynamic Sun: Challenges for Theory and Observations” (ESA SP-600), Danesy, D., Poedts, S., De Groof, A., and Andries, J., Eds., Leuven, Belgium, 2005, id 9.
Su, Y.N. and Huang, G.L., Polarization of loop-top and footpoint sources in microwave bursts, Astrophys. J., 2004, vol. 219, pp. 159–168.
Takakura, T., Limiting polarization of solar microwave emission, Publ. Astron. Soc. Jpn., 1961, vol. 13, pp. 312–320.
Zheleznyakov, V.V. and Zlotnik, E.Ya., O polyarizatsii radiovoln, proshedshikh cherez oblast’ poperechnogo magnitnogo polya v solnechnoi korone, Astron. Zh., 1963, vol. 40, pp. 633–642.