Imaging the solar corona in the EUV

Abstract

The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 Å images the chromosphere and the base of the transition region at a temperature of 5 − 8 × 10 4 K; the Fe IX–X filter at 171 Å images the corona at a temperature of ∼ 1.3 × 10 6 K; the Fe XII filter at 195 Å images the quiet corona outside coronal holes at a temperature of ∼ 1.6 × 10 6 K; and the Fe XV filter at 284 Å images active regions with a temperature of ∼ 2.0 × 10 6 K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection.