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26 April 2024 |
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Article overview
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Re-examining Sunspot Tilt Angle to Include Anti-Hale Statistics | | Bruce H. McClintock
; Aimee A. Norton
; Jing Li
; | | Date: |
16 Dec 2014 | | 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{deg} rather than the more common $pm$ 90{deg}.
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{deg} with a weak preference for east-west alignment 180{deg} 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% $pm$ 0.8% of all bipolar sunspot
regions are misclassified as Hale in traditional catalogs. This percentage is
slightly higher for groups within 5{deg} of the equator due to the
misalignment of the magnetic and heliographic equators. | | Source: | arXiv, 1412.5094 | | Services: | Forum | Review | PDF | Favorites | |
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