Improvements in the determination of ISS Ca II K parameters

TL;DR

This paper discusses recent improvements in data reduction techniques for Ca II K solar observations, enhancing the accuracy of long-term solar activity studies and their application in understanding solar irradiance variability.

Contribution

It introduces new data processing methods for Ca II K measurements from the ISS instrument, improving parameter determination accuracy.

Findings

Enhanced data reduction procedures implemented.

More precise measurements of Ca II K parameters achieved.

Improved understanding of solar activity variations.

Abstract

Measurements of the ionized Ca II K line are one of the major resources for long-term studies of solar and stellar activity. They also play a critical role in many studies related to solar irradiance variability, particularly as a ground-based proxy to model the solar ultraviolet flux variation that may influence the Earth's climate. Full disk images of the Sun in Ca II K have been available from various observatories for more than 100 years and latter synoptic Sun-as-a-star observations in Ca II K began in the early 1970s. One of these instruments, the Integrated Sunlight Spectrometer (ISS) has been in operation at Kitt Peak (Arizona) since late 2006. The ISS takes daily observations of solar spectra in nine spectra bands, including the Ca II K and H line s. We describe recent improvements in data reduction of Ca II K observations, and present time variations of nine parameters derived from the profile of this spectral line.