  Solar prominences are clouds of cool plasma levitating above the solar
surface and insulated from the million-degree corona by magnetic fields. They
form in regions of complex magnetic topology, characterized by non-potential
fields, which can evolve abruptly, disintegrating the prominence and ejecting
magnetized material into the heliosphere. However, their physics is not yet
fully understood because mapping such complex magnetic configurations and their
evolution is extremely challenging, and must often be guessed by proxy from
photometric observations.Using state-of-the-art spectro-polarimetric data, we
reconstruct the structure of the magnetic field in a prominence. We find that
prominence feet harbor helical magnetic fields connecting the prominence to the
solar surface below.
