A novel algorithm for high fidelity spectro-polarimetric snapshot imaging of the low-frequency radio Sun using SKA-low precursor

Abstract

Magnetic field couples the solar interior to the solar atmosphere, known as corona. Coronal magnetic field is one of the crucial parameters which determines the coronal structures and regulates the space weather phenomena like flares, coronal mass ejections, energetic particle events and solar winds [1], [18]. Measuring the magnetic field at middle and higher coronal heights are extremely difficult problem and to date there is no single measurement technique available to measure the higher coronal magnetic fields routinely. polarization measurements of the low-frequency radio emissions are an ideal tool to probe the coronal magnetic fields at higher coronal heights (> 1R⊙). Till date most of the low-frequency polarization observations of the Sun were limited to bright solar radio bursts. Here we developed a novel algorithm for performing precise polarization calibration of the solar observations done with Murchison Widefield Array, a future Square Kilometer Array (SKA) precursor. We have brought down the instrumental polarization < 1%. We anticipate this method will allow us to detect very low level polarised emissions from coronal thermal emissions, which will become a tool for routine measurements of global coronal magnetic field at higher coronal heights. This method can be easily adopted for future SKA and open a window of new discoveries using high fidelity spectro-polarimetric snapshot imaging of the Sun at low radio frequencies.