Measurements of the magnetic field in solar prominences with a spectrally scanning magnetograph

We describe observations with a new magnetograph capable of recording the whole profile of emission lines in prominences. Two recordings are used simultaneously to study the Zeeman effect in circularly polarized light. The spectral scan is produced by the action of piezo ceramics of a Perot-Fabry inter ferometer combined with a narrow band interference filter.The instrument is calibrated using 100% circularly polarized light and an emission line produced in Laboratory conditions in a simulated longitudinal magnetic field. The magnetograph was attached to the large coronagraph (Ø 53 cm) of Kislovodsk to give a series of measurements of the H line of several quiescent and active prominences. The observed values of the longitudinal component of the magnetic field are between: -25 G + 13 G with a noise level at ±2 G for a corresponding resolution of 8 arc sec.Effects produced by the instrumental polarization are discussed.S.A.S. Institut d'Astrophysique du CNRS, 98bis, Bd Arago, F 75014 Paris.