On the Doppler Shift and Asymmetry of Stokes Profiles of Photospheric FeI and Chromospheric MgI Lines
AIR FORCE GEOPHYSICS LAB SUNSPOT NM SOLAR RESEARCH BRANCH
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We analyzed the full Stokes spectra using simultaneous measurements of the photospheric FeI 630.15 and 630.25 nm and chromospheric MgI b2 517.27 nm lines. The data were obtained with the HAONSO Advanced Stokes Polarimeter, about a near disc center sunspot region, NOAA AR 9661. We compare the characteristics of Stokes profiles in terms of Doppler shifts and asymmetries among the three spectral lines which helps us to better understand the chromospheric lines and the magnetic and flow fields in different magnetic regions. The main results are 1 For penumbral area observed by the photospheric FeI lines Doppler velocities derived from Stokes Ivsub i are very close to those derived from linear polarization profiles v sublp but significantly different from those derived from Stokes V profiles vsub zc, which provides direct and strong evidence that the penumbral Evershed flows are magnetized and mainly carried by the horizontal magnetic component. 2 The rudimentary inverse Evershed effect observed by the MgI b2 line provides a qualitative evidence on its formation height that is around or just above the temperature minimum region. 3 zc and lp in penumbrae and zc in pores generally approach their i observed by the chromospheric MgI line, which is not the case for the photospheric FeI lines. 4 Outer penumbrae and pores show similar behavior of the Stokes V asymmetries that tend to change from positive values in the photosphere FeI lines to negative values in the low chromosphere MgI line. 5 The Stokes V profiles in plage regions are highly asymmetric in the photosphere and more symmetric in the low chromosphere. 6 Strong red shifts and large asymmetries are found around the magnetic polarity inversion line within the common penumbra of the spot.
- Atomic and Molecular Physics and Spectroscopy
- Plasma Physics and Magnetohydrodynamics