EDP Sciences
Free access
Volume 404, Number 2, June III 2003
Page(s) L25 - L28
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20030668

A&A 404, L25-L28 (2003)
DOI: 10.1051/0004-6361:20030668


Solar prominence polarimetry

E. Wiehr1 and M. Bianda2

1  Universitäts-Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany
2  Istituto Ricerche Solari, Via Patocchi, 6644 Locarno-Orselina, Switzerland

(Received 7 April 2003 / Accepted 6 May 2003)

We measure the resonance polarization in solar prominences in H $\alpha$, H $\beta$ and HeD 3. A two-dimensional set-up with narrow-band filter, polarization analyzer and CCD camera is used to take prominence images in polarized light at high spatial resolution. Placed on a coudé telescope's hour axis, the observations near the equinoxia are free from purely instrumental polarization. Above the 0.1% noise limit, the Balmer lines do not show a polarization in contrast to the HeD 3 line. Here, we determine the complete polarization profile after exchange of filter and CCD with the spectrograph, keeping the polarization analyzer fixed. In most prominences the Stokes- U and - Q profiles are not similar to Stokes- I: occasionally the blue and the red components of the emission are equal or even show a reverse ratio. This fits calculations for magnetic field strengths of the order of 50 Gauß being markedly stronger than commonly assumed.

Key words: Sun: atmosphere -- Sun: prominences -- instrumentation: polarimeters -- techniques: polarimetry

Offprint request: E. Wiehr, ewiehr@uni-sw.gwdg.de

© ESO 2003