Solar luminosity variation. II - Behavior of calcium H and K at solar minimum and the onset of cycle 21

Abstract

view Abstract Citations (66) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar luminosity variation: II. Behavior of calcium H and K at solar minimum and the onset of cycle 21. White, O. R. ; Livingston, W. Abstract A program for measuring the solar cycle variation of the profiles of Ca ii H and K, using the McMath double-pass spectrometer, is described. The observations are made both at disk center and in integrated light ("the Sun as a star"). During the 2 year epoch covering minimum activity, from 1974 October to 1976 October, the integrated light equivalent width of K as bounded by a 1 A band centered on the line (the K-index) showed no significant variation (cr = 0.22%). Internal error for a single day, over a 7li5 period, is a = 0.066%. During 1977, apparently in response to the onset of cycle 21 activity, the K-index increased by 2.7%, while the central intensity of K3 rose by 5.7%. These changes are traceable in detail to plages on the disk. Center disk observations of the quiet regions containing network and supergranulation cells have shown no change. Subject headings: Ca ii emission - Sun: activity - Sun: plages Publication: The Astrophysical Journal Pub Date: December 1978 DOI: 10.1086/156650 Bibcode: 1978ApJ...226..679W Keywords: Fraunhofer Lines; H Lines; K Lines; Luminous Intensity; Solar Activity; Solar Cycles; Calcium; Calibrating; Emission Spectra; Noise Reduction; Periodic Variations; Secular Variations; Solar Spectra; Solar Spectrometers; Solar Physics; Solar Activity:Solar Spectrum full text sources ADS |