Circular polarization of the CA II H and K lines in solar quiet and active regions

Martinez Pillet, V.; Garcia Lopez, R. J.; del Toro Iniesta, J. C.; Rebolo, R.; Vazquez, M.; Beckman, J. E.; Char, S.
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Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 361, Oct. 1, 1990, p. L81-L85. Research supported by CICYT.

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A representative set of profiles is presented for the Ca II H resonace line in Stokes V and I, for the quiet sun, plages, sunspot umbrae, and a flare, as well as one example of the Ca II K line in a sunspot penumbra. The degree of polarization is highest in the spots and zero in the quiet sun, within error limits. The V profile asymmetries are, however, highest in the flare. The spectra of the Ca II K line are used to obtain a linear relation between V(lambda) and -dI/d(lambda) and a value for B(parallel) of 820 + or - 40 G using the weak-field approximation.