Hp. Jones et al., Analysis of NASA/NSO spectromagnetograph observations for comparison with solar irradiance variations, ASTROPHYS J, 529(2), 2000, pp. 1070-1083
The NASA/NSO Spectromagnetograph (SPM) at the National Solar Observatory/Ki
tt Peak Vacuum Telescope (NSO/KPVT) has produced daily full-disk solar imag
es of line-of-sight (LOS) magnetic flux, LOS velocity, continuum intensity,
equivalent width, and central line depth in either Fe I 550.7 nm or Fe I 8
68.8 nm since 1992 April. Internally, these five images are strictly cospat
ial and cotemporal. This paper describes reduction techniques for removing
spurious effects (principally from clouds and optical vignetting) from the
images and presents summary statistics from the first 2 years of operation.
Pairs of bivariate histograms as well as five-dimensional histograms are f
ormed from the "cleaned" images. Factor analysis of various summary statist
ics from the histograms shows that mixed-polarity magnetic elements of weak
to moderate strength; unipolar magnetic features, including active regions
and strong enhanced network; and sunspots are the most important sources o
f variance in the SPM data. Multiple regressions of spacecraft measurements
of bolometric solar irradiance on the dominant factors, however, yield str
ong correlations with only unipolar regions and sunspots; the weak and mixe
d-polarity features that account for most of the SPM variance are only weak
ly correlated with the spacecraft measurements.