Wavelength Determination for Solar Features Observed by the EUV Imaging Spectrometer on Hinode

Abstract

A wavelength calibration of solar lines observed by the high resolution EUV Imaging Spectrometer (EIS) on the Hinode satellite is reported. Spectral features of the quiet sun and of two mildly active areas were measured and calibrated. A listing of the stronger observed lines with identification of the leading contributor ions is presented. 41 lines are reported, with 90% identified. Wavelength precisions (2$\sigma$) of $\pm$0.0031 Å for the EIS short band and $\pm$0.0029 Å for the EIS long band are obtained. These lines, typical of 1–$2\times 10^{6}$ K plasmas, are recommended as standards for the establishment of EIS wavelength scales. The temperature of EIS varies by about $1\rlap{.}^{\circ}5$ C around the orbit and also with spacecraft pointing. The correlation of these temperature changes with wavelength versus pixel number scale changes is reported.