High Resolution Studies of the Structure of the Solar Atmosphere.
Final rept. 1 Jul 91-31 Jul 95,
SMITHSONIAN ASTROPHYSICAL OBSERVATORY CAMBRIDGE MA
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Our approach has focused on exploring the physical characteristics of the coronal heating mechanisms, as manifested in coronal holes, quiet regions and active regions, using different data sets, data analysis techniques and image processing tools. The main results from these studies can be summarized as follows 1 Temperature inferences in different coronal structures rely on the spectral lines used. Their judicious choice is particularly crucial for reliable inferences in coronal holes. 2 Limits on the helium abundance in the inner corona can be inferred from knowledge of the temperature and density, and their gradients in that region. 3 There exists a characteristic spatial separation of 10-15 between the substructures within coronal holes, that is independent of the temperature of the emitting plasma, or the large scale overlying magnetic field. 4 Different temperature plasmas coexist at coronal heights regardless of the overlying large scale structure, such as active regions, quiet regions or coronal holes, and within these structures. 5 The spatial distribution of the temporal variability of the coronal emission has a very distinct temperature dependence, with a peak at 100,000 K, and is independent of the structure of the overlying large scale magnetic field. 6 In regard to some of the most spectacular forms of dynamic magnetic events, namely corona mass ejections, nonthermal emission as manifested in the form of type I noise storms observed at 90 cm, can serve as predictors for the occurrence of these events.