TY - JOUR AU - Bourdin, Ph. AU - Brandenburg, A. DA - 2018/06/15/ DO - 10.3847/1538-4357/aae97f JF - Astrophys. J. PY - 2018 SE - 2018/06/15/ SP - 3 TI - Magnetic helicity from multipolar regions on the solar surface VL - 869 ER -