TSI modeling: A comparison of ground-based Ca II K-line data with space-based UV images from the SDO/AIA instrument

We explore the use of space-based UV images as a substitute for ground-based Ca II K-line images in modeling Total Solar Irradiance (TSI) variability. The sunspot signal for all 2-component models used here is determined from SFO red continuum images at 672.3 nm. The facular signal is determined from either Ca II K-line images at 393.4 nm or space-based UV images from the Solar Dynamics Observatory AIA experiment at 160 nm and 170 nm wavelengths. Images at both AIA wavelengths are processed with the standard SFO algorithms. The results show good agreement between the fits to Total Solar Irradiance (TSI) variations using ground-based Ca K-line images and the fits to space-based UV images. However, AIA 170 nm images were superior to 160 nm images. The best 2-component fit using ground-based Ca II K-line data was R2 = 0.873; AIA 170 nm produced R2 = 0.896, better than AIA 160 nm’s R2 = 0.793.