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

Abstract

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.

arXiv comment27 pages, 9 figures, Published at the Astrophysical Journal

References in corpus (59)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• LOFAR: The LOw-Frequency ARray
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• Faraday Rotation Measure Synthesis
• The Murchison Widefield Array: Design Overview
• A Review of Solar Type III Radio Bursts
• Science with the Murchison Widefield Array
• Revisiting the radio interferometer measurement equation. I. A full-sky Jones formalism
• The Phase II Murchison Widefield Array: Design Overview
• The Magnetic Field in the Solar Atmosphere
• Real-Time Calibration of the Murchison Widefield Array
• Global maps of the magnetic field in the solar corona
• Nonlinear force-free modeling of the solar coronal magnetic field
• CubiCal - Fast radio interferometric calibration suite exploiting complex optimisation
• Imaging Spectroscopy of Solar Radio Burst Fine Structures
• Coronal Magnetic Field Measurement from EUV Images made by the Solar Dynamics Observatory
• Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)
• A 189 MHz, 2400 square degree polarization survey with the Murchison Widefield Array 32-element prototype
• An all-sky survey of circular polarisation at 200 MHz
• Understanding Instrumental Stokes Leakage in Murchison Widefield Array Polarimetry
• Nonlinear Force-Free Field Extrapolation of a Coronal Magnetic Flux Rope Supporting a Large-Scale Filament from Photospheric Vector Magnetogram
• Fast gain calibration in radio astronomy using alternating direction implicit methods: Analysis and applications
• The challenges of low-frequency radio polarimetry: lessons from the Murchison Widefield Array
• Calibration and Stokes Imaging with Full Embedded Element Primary Beam Model for the Murchison Widefield Array
• Measurements of Photospheric and Chromospheric Magnetic Fields
• Interferometric imaging with the 32 element Murchison Wide-field Array
• FLAGCAL:A flagging and calibration package for radio interferometric data
• Calibration artefacts in radio interferometry. I. Ghost sources in WSRT data
• Interplanetary Scintillation studies with the Murchison Wide-field Array II: Properties of sub-arcsecond compact sources at low radio frequencies
• Interplanetary Scintillation with the Murchison Widefield Array I: A sub-arcsecond Survey over 900 square degrees at 79 and 158 MHz
• Estimation of the physical parameters of a CME at high coronal heights using low frequency radio observations
• In situ measurement of MWA primary beam variation using ORBCOMM
• LOFAR observations of the quiet solar corona
• The POlarised GLEAM Survey (POGS) I: First Results from a Low-Frequency Radio Linear Polarisation Survey of the Southern Sky
• 4D Data Cubes from Radio-Interferometric Spectroscopic Snapshot Imaging
• Estimating solar flux density at low radio frequencies using a sky brightness model
• The Low-Frequency Solar Corona in Circular Polarization
• Evidence for Super-Alfvenic oscillations in sources of Solar type III radio bursts
• The POlarised GLEAM Survey (POGS) II: Results from an All-Sky Rotation Measure Synthesis Survey at Long Wavelengths
• First radio evidence for impulsive heating contribution to the quiet solar corona
• Unsupervised generation of high dynamic range solar images: A novel algorithm for self-calibration of interferometry data
• Direction Dependent Corrections in Polarimetric Radio Imaging I : Characterizing the effects of the primary beam on full Stokes imaging
• VLA Measurements of Faraday Rotation through Coronal Mass Ejections
• A weak coronal heating event associated with periodic particle acceleration episodes
• Calibration errors in interferometric radio polarimetry
• Propagation Effects in Quiet Sun Observations at Meter Wavelengths
• Discovery of correlated evolution in solar noise storm source parameters: Insights on magnetic field dynamics during a microflare
• Characterising coronal turbulence using snapshot imaging of radio bursts in 80-200 MHz
• Direction Dependent Corrections in Polarimetric Radio Imaging II: A-Solver Methodology A low-order solver for the A-Term of the A-Projection algorithm
• A search for counterparts of quiet sun radio transients in extreme ultraviolet data
• Solving for closure errors due to polarization leakage in radio interferometry of unpolarized sources
• Insights from snapshot spectroscopic radio observations of a weak Type I noise storm
• Direction Dependent Corrections in Polarimetric Radio Imaging III: A-to-Z Solver -- Modeling the full Jones antenna aperture illumination pattern
• Robust absolute solar flux density calibration for the Murchison Widefield Array
• Calibration database for the Murchison Widefield Array All-Sky Virtual Observatory
• Polarization Characteristics of Zebra Patterns in Type IV Solar Radio Bursts

Cited by in corpus (11)

• Detection of weak ubiquitous impulsive nonthermal emissions from the solar corona
• Working Principle of the Calibration Algorithm for High Dynamic Range Solar Imaging with Square Kilometre Array Precursor
• Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: Pipeline Implementation
• Deciphering Faint Gyrosynchrotron Emission from Coronal Mass Ejection using Spectro-polarimetric Radio Imaging
• Spectropolarimetric Radio Imaging of Faint Gyrosynchrotron Emission from a CME : A Possible Indication of the Insufficiency of Homogeneous Models
• Preparing for Solar and Heliospheric Science with the SKAO: An Indian Perspective
• Study of radio transients from the quiet Sun during an extremely quiet time
• New Insights into Type-I Solar Noise Storms from High Angular Resolution Spectroscopic Imaging with the Upgraded Giant Metrewave Radio Telescope
• First Robust Detection of Linear Polarization from Metric Solar Emissions: Challenging Established Paradigms
• A Formalism for Calibrating the Instrumental Polarization of Radio Interferometric Arrays at Meter Wavelengths using Unpolarized Sky: A Demonstration using the MWA Observations
• Solar Observation with MeerKAT: Demonstration of Technical Readiness and Initial Science Highlight