Re-examining sunspot tilt angle to include anti-Hale statistics
Article
Article Title | Re-examining sunspot tilt angle to include anti-Hale statistics |
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ERA Journal ID | 1057 |
Article Category | Article |
Authors | McClintock, B. H. (Author), Norton, A. A. (Author) and Li, J. (Author) |
Journal Title | The Astrophysical Journal: an international review of astronomy and astronomical physics |
Journal Citation | 797 (2), pp. 1-10 |
Article Number | 130 |
Number of Pages | 10 |
Year | 2014 |
Publisher | IOP Publishing |
Place of Publication | United States |
ISSN | 0004-637X |
1538-4357 | |
Digital Object Identifier (DOI) | https://doi.org/10.1088/0004-637X/797/2/130 |
Web Address (URL) | https://iopscience.iop.org/article/10.1088/0004-637X/797/2/130 |
Abstract | Sunspot groups and bipolar magnetic regions (BMRs) serve as an observational diagnostic of the solar cycle. We use Debrecen Photohelographic Data (DPD) from 1974-2014 that determined sunspot tilt angles from daily white light observations, and data provided by Li & Ulrich that determined sunspot magnetic tilt angle using Mount Wilson magnetograms from 1974-2012. The magnetograms allowed for BMR tilt angles that were anti-Hale in configuration, so tilt values ranged from 0 to 360° rather than the more common ±90°. We explore the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information. The large scatter of tilt angles over the course of a single cycle and hemisphere prevents Joy's law from being visually identified in the tilt-butterfly diagram without further binning. The average latitude of anti-Hale regions does not differ from the average latitude of all regions in both hemispheres. The distribution of anti-Hale sunspot tilt angles are broadly distributed between 0 and 360° with a weak preference for east-west alignment 180° from their expected Joy's law angle. The anti-Hale sunspots display a log-normal size distribution similar to that of all sunspots, indicating no preferred size for anti-Hale sunspots. We report that 8.4% ± 0.8% of all bipolar sunspot regions are misclassified as Hale in traditional catalogs. This percentage is slightly higher for groups within 5° of the equator due to the misalignment of the magnetic and heliographic equators. |
Keywords | sunspots |
Contains Sensitive Content | Does not contain sensitive content |
ANZSRC Field of Research 2020 | 519999. Other physical sciences not elsewhere classified |
510903. Mesospheric, thermospheric, ionospheric and magnetospheric physics | |
490205. Mathematical aspects of quantum and conformal field theory, quantum gravity and string theory | |
Public Notes | File reproduced in accordance with the copyright policy of the publisher/author. |
Byline Affiliations | School of Agricultural, Computational and Environmental Sciences |
Stanford University, United States | |
University of California, United States | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q2w44/re-examining-sunspot-tilt-angle-to-include-anti-hale-statistics
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