On the measurement of magnetic fields in solar prominences

Measurements of the magnetic fields in solar prominences using the Zeeman effect in the Hα, Hβ and D3 emission lines are described. The polarization is detected along the whole profile of the line. The spectral scanning is produced by the Fabry-Perot interferometer. The electrooptical modulator is a LiNbO3 crystal. The instrumental effects are discussed. A hystogram for the observed values of the longitudinal field has two peaks at 8 and 20 G for prominences in 1979-1982. The second peak relates to the prominences observed at active latitudes (<= +-35 deg). For these prominences, the angle between the long axis of the filament and the line of sight is equal to 2 deg. By comparing the values of the field vector for the prominences of the same epoch, a conclusion is made: the angle between the long axis of the filament and the magnetic field vector is equivalent to the angle between the long axis of the filament and the line of sight, i.e. Bsub(long) approximately B for the prominences of active latitudes