¥ Magnetic full-disk (Sun-as-a-star) indices (sunspot number,
Ca K index, W-B effect, He 10830 equivalent width,
total magnetic flux) all track the 11-year activity cycle, as
expected
¥ The basal, center disk, quiet atmosphere is invariant to the
11-year cycle (Ca K index, C 5380 equivalent width).
Limb darkening is also invariant (+-1%)
¥ The temperature-minimum
layer either tracks a 22-year cycle
or exhibits some other as-yet-unexplained behavior (based
on central intensities of strong photospheric Fraunhofer lines)
¥ Current quiet-Sun model atmospheres do not support these
results.