Structural Invariance of Sunspot Umbrae Over the Solar Cycle: 1993-2004
T.A. Schad, M.J. Penn

TL;DR
This study analyzes 12,967 sunspot umbrae over 11 years, finding that their size, intensity, and magnetic flux relationships remain stable throughout the solar cycle, indicating invariant sunspot structure.
Contribution
It provides the first comprehensive analysis showing the invariance of sunspot umbral properties over a full solar cycle using a large automated dataset.
Findings
Size spectrum shape does not vary with time.
Intensity-magnetic flux relationship remains steady.
Small size variations correlate with the solar cycle but are not significant.
Abstract
Measurements of maximum magnetic flux, minimum intensity, and size are presented for 12 967 sunspot umbrae detected on the NASA/NSO spectromagnetograms between 1993 and 2004 to study umbral structure and strength during the solar cycle. The umbrae are selected using an automated thresholding technique. Measured umbral intensities are first corrected for a confirming observation of umbral limb-darkening. Log-normal fits to the observed size distribution confirm that the size spectrum shape does not vary with time. The intensity-magnetic flux relationship is found to be steady over the solar cycle. The dependence of umbral size on the magnetic flux and minimum intensity are also independent of cycle phase and give linear and quadratic relations, respectively. While the large sample size does show a low amplitude oscillation in the mean minimum intensity and maximum magnetic flux…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
