Spectropolarimetric Imaging of Metric Type III Solar Radio Bursts

Rahman, M. M.; Cairns, Iver H.; McCauley, Patrick

doi:10.1007/s11207-020-01616-0

Cited by 12 publications

(16 citation statements)

References 63 publications

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“…All of the solar data used here was taken under the MWA Project ID G0002. P-AIRCARS usually achieves < |2|% residual leakages for Stokes Q and Stokes U and < |1|% residual leakage for Stokes V. These values are comparable to what is generally achieved for high quality astronomical observations (Lenc et al 2017;Lenc et al 2018;Riseley et al 2018Riseley et al , 2020 with the MWA and much better than those achieved by earlier spectro-polarimetric solar studies (McCauley et al 2019;Rahman et al 2020). P-AIRCARS not only delivers a very small residual leakage, it also provides improved Stokes I imaging fidelity as compared to AIRCARS as shown next.…”

Section: Resultssupporting

confidence: 70%

“…Additionally, the residual instrumental polarization leakages of 1% in all the observations shown in Fig. 9, represent an improvement approaching an order of magnitude over the ∼ 5 − 10% leakages obtained earlier (McCauley et al 2019;Rahman et al 2020). To the best of our knowledge, these are the lowest which have been achieved for any meterwave solar radio images and bring the exciting science target of measuring the weak circular polarization from the quiet Sun within reach.…”

Section: Polarization Images Of the Sun Using P-aircarsmentioning

confidence: 53%

“…The primary merit of Method-I is that it enabled the authors to get to interesting science using an approximate and quick correction of instrumental polarization and circumventing the effort and complexities of developing and implementing a formally correct polarimetric calibration algorithm (McCauley et al 2019;Rahman et al 2020). The ionospheric phases during the solar observations are expected to be significantly different compared to those determined from night time calibrator observation.…”

Section: Previous Attempts and Their Limitationsmentioning

confidence: 99%

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Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm

Kansabanik,

Oberoi,

Mondal

2022

Preprint

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Coronal magnetic fields are well known to be one of the crucial parameters defining coronal physics and space weather. However, measuring the global coronal magnetic fields remains challenging. The polarization properties of coronal radio emissions are sensitive to coronal magnetic fields. While they can prove to be useful probes of coronal and heliospheric magnetic fields, their usage has been limited by technical and algorithmic challenges. We present a robust algorithm for precise polarization calibration and imaging of low-radio frequency solar observations and demonstrate it on data from the Murchison Widefield Array, a Square Kilometer Array (SKA) precursor. This algorithm is based on the Measurement Equation framework, which forms the basis of all modern radio interferometric calibration and imaging. It delivers high dynamic range and fidelity full Stokes solar radio images with instrumental polarization leakages < 1%, on par with general astronomical radio imaging, and represents the state-of-the-art. Opening up this rewarding, yet unexplored, phase space will enable multiple novel science investigations and offer considerable discovery potential. Examples include detection of low-level of circularly polarization from thermal coronal emission to estimate large-scale quiescent coronal fields; polarization of faint gyrosynchrotron emissions from coronal mass ejections for robust estimation of plasma parameters; and detection of the first-ever linear polarization at these frequencies. This method has been developed with the SKA in mind and will enable a new era of high fidelity spectro-polarimetric snapshot solar imaging at low-radio frequencies.

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Section: Resultssupporting

confidence: 70%

Section: Polarization Images Of the Sun Using P-aircarsmentioning

confidence: 53%

Section: Previous Attempts and Their Limitationsmentioning

confidence: 99%

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Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm

Kansabanik,

Oberoi,

Mondal

2022

Preprint

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“…Both provide imaging spectroscopy of the radio Sun at high temporal resolution on an occasional basis. Several studies have been published in recent years that take advantage of these novel instruments to investigate both active and quiet Sun (e.g., Mann et al 2018;Reid & Kontar 2018;Sharykin et al 2018;Sharma et al 2018;Zucca et al 2018;McCauley et al 2019;Mondal et al 2020;Rahman et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

Chhabra

Gary

Hallinan

et al. 2021

ApJ

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We present the first results of a solar radio event observed with the Owens Valley Radio Observatory Long Wavelength Array at metric wavelengths. We examine a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M2.1 GOES soft X-ray flare from 2015 September 20. Images of 9 s cadence are used to analyze the event over a 120 minute period, and solar emission is observed out to a distance of ≈3.5 R e , with an instantaneous bandwidth covering 22 MHz within the frequency range of 40-70 MHz. We present our results from the investigation of the radio event, focusing particularly on one burst source that exhibits outward motion, which we classify as a moving type IV burst. We image the event at multiple frequencies and use the source centroids to obtain the velocity for the outward motion. Spatial and temporal comparison with observations of the CME in white light from the C2 coronagraph of the Large Angle and Spectrometric COronagraph, indicates an association of the outward motion with the core of the CME. By performing graduated-cylindrical-shell reconstruction of the CME, we constrain the density in the volume. The electron plasma frequency obtained from the density estimates do not allow us to completely dismiss plasma emission as the underlying mechanism. However, based on source height and smoothness of the emission in frequency and time, we argue that gyrosynchrotron is the more plausible mechanism. We use gyrosynchrotron spectral-fitting techniques to estimate the evolving physical conditions during the outward motion of this burst source.

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“…There has not been much recent works using polarization information in imaging spectroscopy as calibration issues complicate matters. A recent work (Rahman et al, 2020) looked at the polarization of type IIIs using the MWA. They found the degree of circular polarization increased as a function of frequency and was higher at the start of the radio bursts, consistent with previous models that fundamental emission is generated first.…”

Section: Low Frequency Burstsmentioning

confidence: 99%

A Review of Recent Solar Type III Imaging Spectroscopy

Reid

2020

Front. Astron. Space Sci.

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Spectropolarimetric Imaging of Metric Type III Solar Radio Bursts

Cited by 12 publications

References 63 publications

Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm

Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

A Review of Recent Solar Type III Imaging Spectroscopy

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