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6th of September 2019
MWA solar imaging
by McCauley et al.
McCauley et al. present spectropolarimetric imaging observations of the solar corona at low frequencies (80 – 240 MHz) using the Murchison Widefield Array (MWA). A new algorithm was developed to mitigate an instrumental artefact by which the total intensity signal contaminates the polarimetric images due to calibration errors. A range of circular polarization (Stokes V) features are detected in images of the sun. Compact polarized sources are detected with polarization fractions ranging from less than 0.5% to nearly 100% and are interpreted as a continuum of plasma emission noise storm (Type I burst) sources associated with active regions. The image above shows an example of a compact polarized sources detected at 161 MHz. The title corresponds to the UTC time followed by the peak polarization fraction in parentheses. The color scale is linear and the color bar intensities are expressed in units of signal-to-noise [σ], and the green contour reflects the 5-σ level in Stokes I. Black ellipses around the sources show the region identified by the source finder algorithm. The large solid circles represent the optical disk, and the ellipses in the lower-left corners represent the synthesized beam sizes More details are given in the preprint of the paper, which will appear in Solar Physics.

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