Astronomy & Astrophysics

Table 1: Observational data and results of interpretation. From left to right: observational data: date, limb distance $d_{{\rm limb}}$ , cosine of the heliocentric angle $\mu$ , ratio of line center intensity to the neighboring continuum intensity $I_{{\rm cent}}/I_{{\rm cont}}$ , line center linear polarization degree p (Q/I of Fig. 1), theoretical continuum polarization degree $p_{{\rm cont}}$ (see text); results of interpretation: height of formation of the line center above the $\tau _{5000}=1$ level h (see text for its definition), microturbulent velocity $v_{{\rm micro}}$ , macroturbulent velocity $v_{{\rm macro}}$ , mircoturbulent magnetic field strength B, field strength in Hanle relative units ( $\Gamma$ parameter, see Sect. 3.2), where the value 1 corresponds to the maximum of sensitivity.
Table 2: Positions of the two quarter-wave plates (QWP1 and QWP2) of the analyzer, and resulting output signals after the beam splitter (last column). The first column gives the conventional name of the setting of the polarimeter. QWP1 is the first plate encountered by the Sun's light.