Methods of Detecting Polar Coronal Holes in the EUV
Abstract
One method of forecasting the peak amplitude of future solar cycles uses the polar magnetic field strength at solar minimum to predict the value of the upcoming maximum. Because the polar field is closely related to the polar coronal hole, we would like to consider the size and shape of the polar hole on the prediction. We measure the perimeter of polar coronal holes over solar cycle 23 as they appear on the limb of the sun in 171, 195, and 304 Å\ solar images from the Extreme ultraviolet Imaging Telescope (EIT) on SOHO. The area within the perimeter can easily be determined. Taking measurements on the limb minimizes the effects of differences in scale height between the material emitting the various wavelengths. Perimeter tracking also allows for the coronal rotation rate to emerge organically from the data rather than forcing a period on the data. This method should help to improve our estimates of the size and shape of the polar coronal holes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMSH13A1099K
- Keywords:
-
- 3225 Numerical approximations and analysis (4260);
- 7511 Coronal holes