Anisotropic Radio-wave Scattering and the Interpretation of Solar Radio Emission Observations

0523127 - ÚFA 2020 RIV US eng J - Článek v odborném periodiku
Kontar, E. P. - Chen, X. - Chrysaphi, N. - Jeffrey, N.L.S. - Emslie, A.G. - Krupař, Vratislav - Maksimovic, M. - Gordovskyy, M. - Browning, P.K.
Anisotropic Radio-wave Scattering and the Interpretation of Solar Radio Emission Observations.
Astrophysical Journal. Roč. 884, č. 2 (2019), č. článku 122. ISSN 0004-637X. E-ISSN 1538-4357
Grant CEP: GA ČR(CZ) GJ17-06818Y
Institucionální podpora: RVO:68378289
Klíčová slova: coronal scattering * III bursts * wind * propagation * plasma * directivity * wavelenghts * simulation * turbulence * evolution
Obor OECD: Fluids and plasma physics (including surface physics)
Impakt faktor: 5.746, rok: 2019
Způsob publikování: Open access
https://www.research.manchester.ac.uk/portal/files/160060006/Kontar_2019_ApJ_884_122.pdf

The observed properties (i.e., source size, source position, time duration, and decay time) of solar radio emission produced through plasma processes near the local plasma frequency, and hence the interpretation of solar radio bursts, are strongly influenced by propagation effects in the inhomogeneous turbulent solar corona. In this work, a 3D stochastic description of the propagation process is presented, based on the Fokker-Planck and Langevin equations of radio-wave transport in a medium containing anisotropic electron density fluctuations. Using a numerical treatment based on this model, we investigate the characteristic source sizes and burst decay times for Type III solar radio bursts. Comparison of the simulations with the observations of solar radio bursts shows that predominantly perpendicular density fluctuations in the solar corona are required, with an anisotropy factor of similar to 0.3 for sources observed at around 30 MHz. The simulations also demonstrate that the photons are isotropized near the region of primary emission, but the waves are then focused by large-scale refraction, leading to plasma radio emission directivity that is characterized by a half width at half maximum of about 40 degrees near 30 MHz. The results are applicable to various solar radio bursts produced via plasma emission.
Trvalý link: http://hdl.handle.net/11104/0307526