EUV measurements and solar active region models

It is shown that model calculations in general can act as a good tool for d iagnostics of the coronal plasma. In the special case of microwave emission models (S-component and burst radiation), the relatively high number of fr ee parameters requires additional observations in other wavelength ranges. For instance, from EUV and Xray data information on electron temperatures a nd densities of solar active regions (SAR) can be derived. Evaluating spati ally resolved measurements from Yohkoh, SOHO, TRACE; and other missions, so lar spectral irradiance data of improved accuracy and high temporal resolut ion as to be expected from EUV-PHOCA and SOL-ACES experiments will contribu te to the improvement of SAR models. (C) 2000 Elsevier Science Ltd. All rig hts reserved.