| Name: | Puja Majee |
| Affiliation: | National Centre for Radio Astrophysics |
| Conference ID : | ASI2024_397 |
| Title : | First detailed polarimetric study of a type-II solar radio burst with the Murchison Widefield Array |
| Authors : | Puja Majee1, Devojyoti Kansabanik1, Divya Oberoi1
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| Authors Affiliation: | 1 National Centre for Radio Astrophysics, Pune-411007, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Sun, Solar System, Exoplanets, and Astrobiology |
| Abstract : | Type-II solar radio bursts are plasma emissions generated by magnetohydrodynamic shocks that are predominantly driven by coronal mass ejections (CMEs), the most potent drivers of space weather. This narrow-bandwidth (~few MHz) emissions show slow drift towards lower frequencies in the dynamic spectrum and appear at the fundamental and harmonic of the local plasma frequency. The evolution and geo-effectiveness of CMEs are governed by their magnetic fields and interaction with the coronal magnetized plasma. Therefore, understanding the CME-entrained magnetic fields and the ambient medium is important. Polarimetric properties of type-II bursts provide very promising diagnostics for measuring and understanding the magnetic field strength, and topology at the CME-shocks. In literature, their polarization properties have been reported from unpolarized to very strong circularly polarized and no linear polarization has ever been reported. The vast majority of these studies rely on dynamic spectra which only provide spatially integrated information. Instruments like Murchison Widefield Array (MWA) and robust spectropolarimetric snapshot solar imaging pipeline, P-AIRCARS, (Kansabanik et al., 2022, 2023) have enabled high-fidelity and high-dynamic range solar radio imaging with good temporal, spectral and reasonable angular resolution. Benefiting from these, we have used the MWA to carry out detailed polarimetric characterization of a type-II solar radio burst. The imaging detection of circular polarization, in line with previous studies, is a significant milestone. We also report the first imaging detection of low levels of linearly polarized type-II emission. This robust but surprising detection goes against the conventional wisdom that differential coronal Faraday rotation should wipe out any signatures of linear polarization in coronal emissions. We characterize the polarimetric structures in both circular and linear polarizations, meticulously investigating their temporal and spectral evolutions. Our study marks the start of the use of polarimetric imaging observations to further the understanding of type-II radio bursts and coronal propagation.
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