The EIT instrument aboard SOHO obtains full disk images of the Sun through four channels at Fe IX,X (171 A), Fe XII (195 A), Fe XV (284 A), and He II (304 A). We construct a model differential emission measure (DEM) map, using the EIT images from the four channels which accurately covers the temperature range 80,000 - 2.2 MK. We use the DEM map to calculate absolutely calibrated images of individual lines or passbands in addition to the four EIT channels. The validity of our model is shown with a long term comparision to the SOHO SEM instrument full disk irradiances. An important application presented here is the time history from 1996-2000 of the pure He II (304 A) solar irradiance. Additional spatial and spectral comparisons can be done using the SOHO CDS instrument and the SERTS rocket flight.
AAS/Solar Physics Division Meeting #31
- Pub Date:
- May 2000