The Relative Intensity Calibration of Hinode/EIS and SOHO/SUMER

Abstract

In this work, we have used simultaneous observations of the quiet Sun above the solar west limb obtained with the Hinode/Extreme ultraviolet Imaging Spectrograph and SOHO/SUMER instruments to determine their relative intensity calibration. We used two different methods: intensity ratios of lines emitted by the same upper level and observed in the spectral ranges of the two spectrometers, and the determination of the differential emission measure and total emission measure of the plasma. We review the uncertainties in our analysis and conclude that the relative calibration of the two instruments, as it can be determined from the standard data reduction software of each of them, is correct within uncertainties.