Reduction and Analysis of He I 1083 NM Spectra-Spectroheliograms

Details Reduction and Analysis of He I 1083 NM Spectra-Spectroheliograms Reduction and Analysis of He I 1083 NM Spectra-Spectroheliograms

May 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997spd....28.0225j&link_type=abstract

American Astronomical Society, SPD meeting #28, #02.25; Bulletin of the American Astronomical Society, Vol. 29, p.897

Astronomy and Astrophysics

Astronomy

Scientific paper

Over two decades of synoptic 1083 nm data from the National Solar Observatory/Kitt Peak Vacuum Telescope (NSO/KPVT) attest to the fact that satisfactory equivalent width images may be obtained from simple sums over ``line''and ``continuum'' bandpasses. However, much more care is needed to extract Doppler velocity, line depth, and asymmetry since the 1083 nm line typically has line depths of only a few percent and is blended with both telluric water vapor and the red wing of a nearby Si I line at 1082.8 nm. We present a new algorithm for analysis of He I 1083 nm data obtained with the NASA/NSO Spectromagnetograph (SPM) at the KPVT. A linear fit to intensity averages over bands near 1082.4 nm and 1083.6 nm specifies the continuum intensity across the wavelength domain of interest. The spectral algorithm currently used for 868.8 nm SPM magnetograms computes line-center wavelengths and depths for the strong adjacent telluric and Si lines. Quick fits of the damping wings of these features together with a scaled profile of the weak water vapor feature which is coincident in wavelength with the 1083 nm line (Breckenridge and Hall, 1973: Solar Phys. 28, 15) are removed from the spectral region containing the 1083 nm line. The spectral algorithm then computes the central wavelength and line depth of the 1083 nm line. An extension of this algorithm locates the bisector at the 0.35 central line-depth position on the profile to compute a line asymmetry parameter (Dupree, Penn, and Jones, 1976: ApJ 467, L121). We show sample results of the algorithm applied both off-line to spectra-spectroheliograms and on-line to spatial-spectral data as they are acquired.

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