Thesis

Investigating the relationship between Stokes' profiles and line-of-sight magnetic fields

Using observations of Stokes I and V profiles of the CaII 8542 Å absorption line produced in the solar chromosphere, the magnetic and velocity properties of active regions are investigated. Results for several active regions in Solar-Cycle 24 with varying degrees of activity are presented. The studied properties include area and amplitude asymmetry, net circular polarization, and differences between Stokes V and the change in Stokes I with respect to wavelength (dI/dλ). These parameters are compared with the line-of-sight magnetic field, BLOS, to determine their relationships. Data was acquired with the Vector Spectromagnetograph (VSM), operated by the National Solar Observatory's Synoptic Optical Long-term Investigations of the Sun telescope. The ground-based VSM provides Zeeman-induced Stokes profiles as well as the line-of-sight magnetograms from which BLOS is inferred. Line asymmetries and net circular polarization are in agreement with expected spatial results, and similar dependences on BLOS appear regardless of solar flare activity. Furthermore, it is concluded that Stokes V is proportional to BLOS and dI/dλ.

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