A Comprehensive Assessment of EUV Polar Coronal Holes: 1996 - 2018
Abstract
Polar Coronal Holes are the longest-lived features on the sun and are a critical piece to understand the global state of the solar corona. Because of the oblique viewing angle, obstruction due to the coronal plasma scale height, and lack of ground truth make segmentation of polar holes difficult. We make new measurements of polar hole's perimeter and area in three EUV wavelengths between 1996 and 2018 using five different space-based imagers: SOHO EIT, STEREO A and B EUVI, PROBA2 SWAP, and SDO AIA. The generated time-series of coronal hole parameters rarely agree with each other, which presents a difficult data problem: multi-band, multi-instrument, heteroscedastic measurements with periodic and systematic signals. We combine these measurements using a parametric bootstrap method to make an empirical estimation of the polar coronal hole's size, boundary, and center of mass. This technique allows us to simultaneously analyze the physical properties of polar coronal holes and identify regular periodicities in our data from other origins. We present a comprehensive view of the EUV polar coronal hole over the past 22 years.
- Publication:
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American Astronomical Society Meeting Abstracts #234
- Pub Date:
- June 2019
- Bibcode:
- 2019AAS...23412501K