Initial results from the XUV Doppler Telescope Original Research Article

We developed a unique telescope to obtain simultaneous XUV images and the velocity maps by measuring the line-of-sight Doppler shifts of the Fe XIV 211 Å line (T = 1.8 MK): the Solar XUV Doppler Telescope (hereafter XDT). The telescope was launched by the Institute of Space and Astronautical Science with the 22nd S520 rocket on January 31, 1998, and took 14 XUV whole sun images during 5 minutes. Simultaneous observations of XDT with Yohkoh (SXT), SOHO (EIT, CDS, LASCO and MDI) were successfully carried out. The images taken with EIT, XDT and SXT are able to cover the wide temperature ranging from 1 to 10 MK, and clearly show the multi-temperature nature of the solar corona. Indeed, we notice that both the cool (1–2 MK) loops observed with EIT and XDT, and the hot (>3 MK) loops observed with SXT exist in the same active regions but in a spatially exclusive way. The XDT red-blue ratio between longer- and shorter-wavelength bands of Fe XIV 211 Å line indicates a possible down-flow of 1.8 MK plasma near the footpoints of multiple cool loops.