Abstract:The physical state of matter at the base of the coronal hole at the level of the chromosphere was studied from observations in the Hα and He I 10830 Å lines. The polar coronal hole was observed in the northern hemisphere in 2015-2017 during 24 Carrington rotations. Boundaries of the coronal hole were determined from observations in the 193 Å line. Intensities in the lines were expressed in units of the unperturbed Sun. For the He I 10830 Å line, the relative intensity of coronal holes varied within 1.0046-1.03… Show more
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