The aim of the present project is the investigation of physical conditions in flares and solar active regions. The investigations will be based on interpretation of X-ray spectra observed by the Bent Crystal Spectrometer (BCS) aboard the NASA Solar Maximum Mission (SMM) spacecraft. These observed spectra are still the best in astrophysics.

Advanced spectral analysis tools will be used, some of them under development. The following parameters characterizing a hot emitting plasma will be determined and their time dependences studied:

• Elemental abundances for Ca and Fe
• Electron distribution functions and their possible deviations from Maxwellian
• Differential (over temperature) emission measure distributions
• Microturbulence and their envisaged centre to limb changes
• Directed plasma flows causing Doppler line shifts
• Ionisation state of flaring plasmas and its possible non-equilibrium states

We will compare the reduced BCS spectra with respective laboratory counterparts observed in Tokamaks and Electron Beam Ion Traps (EBIT). Attention will be focused on dependence of physical conditions withe the age of active region and/or phase of the activity cycle.

Reduction of ~200 000 spectra available from NASA archives will be performed. Spectral irradiance will be expressed in units of [phot cm^-2 s^-1 Å^-1] using the most recent calibration data. Spectra of Ca and Fe He-like ions will be studied using CHIANTI atomic database. Using Cowan atomic code supporting calculations of many so-called satellite line intensities will be calculated which will improve the fit between synthetic and observed spectra.