A CDS Observation of the Relationship Between a Coronal Hole and Chromospheric Structure

This paper studies the relationship between chromospheric structure and the location of the coronal hole boundary, using a SOHO-CDS observation made on 13 June 1996. The cell structure visible in the oxygen and helium data is smoothed and a basin algorithm is used to find the individual cells. As the smoothing scale increases, cells merge to form larger ones. A trade off between merging and smoothing was made, a scale of 5,000 km being used. There is good agreement between the edges of cells and the coronal hole boundary, as determined in Mg IX 368 Å, although it is not perfect. This preliminary analysis shows that the coronal hole boundary is located along chromospheric network cell edges in most places, as would be expected if the chromosphere is the source of the coronal structure and solar wind.