Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two New Methods for Counting and Tracking the Evolution of Polar Faculae   Polar faculae (PFe) are the footpoints of magnetic field lines near the Sun's
poles that are seen as bright regions along the edges of granules. The time
variation in the number of PFe has been shown to correlate with the strength of
the polar magnetic field and to be a predictor of the subsequent solar cycle.
Due to the small size and transient nature of these features, combined with
different techniques and observational factors, previous counts of PFe differ
in magnitude. Further, there were no scalable techniques to measure the
statistical properties of faculae. Using data from the Helioseismic and
Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), we present
two new methods for tracking faculae and measuring their properties. In the
first, we calculate the standard deviation of the HMI images over one day,
visualizing the faculae as streaks. The facular lifetime is found by dividing
the angular streak length by the latitude-dependent rotation rate. We apply
this method to 134 days of data over 11 years. The distribution of facular
lifetimes has a mean of 6.0 hours, a FWHM of 5.4 hours, and a skew towards
longer lifetimes, with some lasting up to 1 day. In the second method, we
overlay images of the progressive standard deviation with the HMI magnetogram
to show the close relationship between facular candidates and the magnetic
field. The results allow us to distinguish between motion due to the Sun's
rotation and "proper motion" due to faculae moving across the Sun's surface,
confirming that PFe participate in convective motions at the poles. Counts of
PFe using both methods agree with previous counts in their variation with the
solar cycle and the polar magnetic field. These methods can be extended to
automate the identification and measurement of other properties of of PFe,
which would allow for daily measurements of all faculae since SDO began
operation in 2010.

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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: cs
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: physics
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The categories of this paper are: q-bio