CAOSP abstracts, Volume: 32, No.: 2, year: 2002

Abstract: To clarify the possible influence of the coronal magnetic field on the degree of polarization p, direction of polarization β, and line intensity I_λ measured during the 11 July 1991 total solar eclipse, we have compared these quantities with different field parameters. The structure of the coronal magnetic field on the eclipse day was calculated using potential approximation. The relation of p and I_λ as measured at 1.2 R_Sun from the centre of the solar disk to the strength of the magnetic field and its different components is discussed in detail. It is found that the points pertinent to the large-scale coronal structures of different morphological (physical) types (high-latitude streamers, bright equatorial regions, regions in the vicinity of coronal holes, etc.) form isolated, not overlapping clusters of points on the B -- p, B -- β and B -- log I_λ diagrams. Two classes of objects are distinct in these diagrams. The first class comprises of high-latitude streamers in which the degree of polarization increases with decreasing B. The second class is represented by coronal condensations, moderately active equatorial regions, and coronal holes. In the objects of this class, the magnetic field strength is approximately three times as large as in the streamers, and the degree of polarization depends only weakly on B. It is shown that p, I_λ and β display a noticeable relationship with the indices Q_1 and Q_2, which we introduced to characterize the complexity (degree of inhomogeneity) of the magnetic field at any given point in the solar corona. In fact, Q_1 and Q_2 represent the absolute and relative deviations of B from its mean value measured in the neighbourhood of a given point.

The results of our investigation suggest that we are dealing with the direct influence of the magnetic field on the generation of the polarized radiation in the λ 530,3nm emission line. One can expect, therefore, that the investigation of polarization characteristics would provide a useful method for determining the magnetic field in the solar corona.

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