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NOAO Newsletter - National Solar Observatory - September 2000 - Number 63


Understanding Spectroheliograms --- Insights from Spectral Line Analysis

K. S. Balasubramaniam

In an effort to seek newer diagnostic tools for monitoring solar activity, L.A. Smaldone and O. Scognamiglio (University of Naples), and K. S. Balasubramaniam (NSO) have reconstructed spectroheliograms in various spectral lines in the range 3900-3940 (around the Ca II K line) from high spatial and spectral resolution measure-ments. In active regions, they find that the spectroheliogram features in a number of spectral lines are similar to the Ca II K1v spectro-heliogram features. In plages, on the contrary, only spectroheliograms in a few spectral lines correlate with the Ca II K1v. In plages, the best correlation is with the Si I 3905. From these measurements, they have developed contrast functions to isolate various active phenomena as seen in Ca II and compare its formation contribution of relative velocities, magnetic fields, and intensity as seen in Fe I and Si I spectral lines. These indicators provide insight into the formation of the Ca II K line.


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