Automated Coronal Hole Detection using He I 1083 nm Spectroheliograms and Photospheric Magnetograms

Abstract

A method for automated coronal hole detection using He I 1083 nm spectroheliograms and photospheric magnetograms is presented here. The unique line formation of the helium line allows for the detection of regions associated with solar coronal holes with minimal line-of-sight obscuration across the observed solar disk. The automated detection algorithm utilizes morphological image analysis, thresholding and smoothing to estimate the location, boundaries, polarity and flux of candidate coronal hole regions. The algorithm utilizes thresholds based on mean values determined from over 10 years of the Kitt Peak Vacuum Telescope daily hand-drawn coronal hole images. A comparison between the automatically created and hand-drawn images for a 11-year period beginning in 1992 is outlined. In addition, the creation of synoptic maps using the daily automated coronal hole images is also discussed.