Magnetic maps of prominences from full Stokes analysis of the He I D3 line

We present the first magnetic maps of a prominence, derived from inversion of spectropolarimetric data in He I D3 using the principal component analysis of all four Stokes profiles. This prominence, along with several others, was observed in 2002 May using the Dunn Solar Telescope of the National Solar Observatory/Sacramento Peak Observatory, equipped with the High Altitude Observatory Advanced Stokes Polarimeter. The use of an unocculted instrument allowed us to map the prominence magnetic fields down to the chromospheric limb. Our analysis indicates that the average magnetic field in prominences is mostly horizontal and varies between 10 and 20 G, thus confirming previous findings. However, our maps show that fields significantly stronger than average, even as large as 60 or 70 G, can often be found in clearly organized plasma structures of the prominence.