LAUSR

Observations in the HeI 10830 Å and Hα lines are used to study the physical conditions in a polar coronal hole. The coronal hole was observed in the northern hemisphere from June 2015 through March 2017. The range of intensity variations in the coronal hole in the HeI 10830 Å line was 1.0046-1.0355 relative to the intensity of the unperturbed Sun and in the Hα line, 0.9676-0.9753. The intensities of the coronal hole were calculated for different models of the chromosphere in order to explain the observed features. The temperature and density in the coronal hole were determined as functions of the column density in the chromosphere. The calculations were based on calculations of the HeI 10830 Å and Hα line profiles using a non-LTE program. At the level of the chromosphere the temperature in the coronal hole is lower by 500-1500 K than the unperturbed chromosphere and the density is lower by a factor of 2-3.