Primary and Secondary Solar Polar Crown PILs over Five Solar Cycles
Abstract
Solar filaments are located on polarity inversion lines (PILs) on the sun. Polar crown filaments are found at high helio-latitudes, but usually encircle the Sun for a brief period prior to the polarity reversal around solar maximum. Usually, there are polar crown gaps in both hemispheres, where coronal holes extend from the polar regions to lower latitudes. We undertake a five solar-cycle (SC19-23) study of the high latitude polar crown PILs that encircle the sun each solar cycle using the McIntosh Archive. The McIntosh Archive consists of a set of hand-drawn solar synoptic (Carrington) maps created by Patrick McIntosh from 1964 to 2009 (SC20-23) using H-alpha images and magnetograms for PILs, and He-I 10830A images for coronal holes since 1974. Most of these maps have now been digitized, with some gaps in SC20 and SC21. We also digitized the Carrington maps created from Kodaikanal Solar Observatory data in India by Makarov and Sivaraman (1986) to extend the study back through SC19. We focus on the large unipolar magnetic cells which are prominent on the sun after sunspot minimum, and then the 'rush-to-the-poles' in the ascending part of the solar cycle before the polarity reverses in the polar regions. PILs form at the boundaries of the opposite-polarity cells. The primary polar crown PIL is at the highest latitudes, but a secondary polar crown PIL becomes visible during the 'rush-to-the-poles' (McIntosh, 2003). The secondary PIL lies about 10 degrees or more equatorward of the primary PIL, which disappears at high latitudes while the secondary PIL becomes the primary PIL around 55 degrees north and south. We look at the evolution of the maximum latitude of these primary and secondary PILs as well as their median locations. We calculate the slope of the 'rush-to-the-poles', and we see what the hemispherical differences are and between solar cycles. Our results on the two polar crown PILs inform us about the solar dynamo activity in the interior of the sun and help constrain dynamo models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH13B..08E
- Keywords:
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- 7599 General or miscellaneous;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7899 General or miscellaneous;
- SPACE PLASMA PHYSICS;
- 7999 General or miscellaneous;
- SPACE WEATHER