Calibration of TRACE Lyman-α images using SOHO/SUMER observations

Abstract

1216 Å channel images from the Transition Region and Coronal Explorer (TRACE) contain not only the desired HI Lyman-α (Lα) line emission from the Sun, but also some UV continuum around 1600 Å. By comparing TRACE data with Lα images from the Very High Angular Resolution Ultraviolet Telescope, Handy et al. proposed a simple procedure to remove the contamination: a linear combination of 1216 Å and 1600 Å channel images from the TRACE. In order to check the reliability of this procedure, here we compare TRACE data with Lα raster scan images from the SUMER instrument onboard the Solar and Heliospheric Observatory (SOHO). We obtain a linear combination coefficient very similar to that of Handy et al., and also find that the apparent spatial resolution of the Lα raster scan images from SOHO/SUMER is at least 4 arcsec × 4 arcsec, which is more than 2-4 times lower than that of its single spectrum.