Magnetic field and plasma diagnostics from coordinated prominence observations

We study from a statistical point of view the magnetic field in prominences by using THEMIS in the MTR mode performing spectro-polarimetry of the He D3 line.
Combining these measurements with spectroscopic data from IRIS, SOHO/EIS and ground-based telescopes (Meudon Solar Tower, Fuxian Solar Observatory, Ondrejov, Bialkow we determine the inferred temperature, density, and flow velocities of the plasma.
Multiple questions are open:
- What is the general orientation of the magnetic field in prominences? Is the model using a single orientation of magnetic field always valid for atypical prominences?
- Does this depend on the location of the filament on the disk (visible in Halpha, in He II 304) over an inversion line between weak or strong network?
- The study of the differential emission measure using Hinode/EIS data informs us about the plasma parameters of the prominences: are prominences in a weak environment field dominated by gas pressure?
- Measuring the Dopplershifts in Mg II lines (with IRIS) and in Halpha can tell us if there are substantial velocities to maintain vertical rotating structures, as it is suggested with tornado-like prominences.
We shall give some results obtained with different ground-based and space instruments in this framework.