High resolution solar magnetometry with the spectrograph of the Pic du Midi Turret Dome

¹ LESIA, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France e-mail: Jean-Marie.Malherbe@Obspm.Fr
² Laboratoire d'Astrophysique, Observatoire Midi Pyrénées, 57 Avenue d'Azereix, PB 826, 65008 Tarbes Cedex, France

Accepted: 23 July 2004

Abstract

We present the first results obtained with a new Ferroelectric Liquid Crystal (FLC) polarimeter operating with the spectrograph of the Pic du Midi Turret Dome, since September 2003. We observed the solar granulation around active region NOAA 0459 with the Multichannel Subtractive Double Pass (MSDP) operating mode and analysed the circular polarization of the Na D1 589.6 nm spectral line in terms of longitudinal magnetic fields in a 2D field of view ( arcsec). Image quality was fairly good and limited to 0.4 arcsec due to the pixel sampling. This observation reveals the presence of magnetic concentrations of several hundred Gauss which are mainly located in the intergranular lanes. Data analysis performed at two different optical depths (line core and line wings) also suggests that magnetic lines are curved and diverge with increasing altitude.