This project will use a recently developed Non-Linear Fore- Free (NLFF) model (Wu et tal. 1990) to study the magnetic configuration and structure of sunspots and active regions. The PI will use magnetogram observations obtained with the MSFC vector magnetograph (photosphere) together with correlated observations in UV and X-rays (transition region and corona) from SMM. Supporting observations in H and in radio wavelength also will be used. The main objectives are: (i) to derive the three-dimensional magnetic field configuration and physical structure in well-observed sunspots and active regions, based on multi-level observations using the NLFF model. (ii) to compare the calculated magnetic field configurations, i.e. 3-D current system and loop structures with those observed in UV and X-rays in order to identify local regions of high current density and field gradient in various atmospheric levels that are associated with flare energy build up and release processes. By comparing the model calculations with observations, the project will test the capability and accuracy of the newly developed NLFF model, and (iii) further develop regularization technique for NLFF calculations. #
