Global Pattern of the Magnetic Field Vectors Above Neutral Lines from 1974 to 1982: Pic-du-Midi Observations of Prominences
Résumé
The magnetic field vectors derived from the Hanle effect measured in
prominences during the ascending phase and maximum of Cycle XXI have been
plotted on the corresponding synoptic maps of the Meudon Observatory. Most
of these measurements have been performed in a single line, He I D3.
Our previous analysis of 2 lines measurements have already proved that the
prominences magnetic field has the Inverse polarity and remains close to
the horizontal plane (Bommier et al., 1994, Solar Physics 154, 231; Bommier
et al., 1986, A&A 156, 79). We had also found early that the field
component along the filament axis shows a remarkable large scale pattern,
especially at high latitudes (Leroy et al., 1983, Solar Physics 83, 135).
Given the geometry of horizontal Inverse field, we reinvestigate this large
scale organization through our complete set of observations (300
prominences). These new maps fully confirm and extend to medium latitudes
the law of reversal of the axial field from one prominence band to the
adjacent ones. This behavior, together with the Inverse polarity pattern,
gives a picture consistent with a North-South global field distorded by the
differential rotation.