Magnetic fields beneath active region coronal loops

Significantly, the minority fields are situated greater than or similar to 12 '' from bright footpoints. We use physical arguments to show that any unresolved minority flux cannot reach coronal footpoints adjacent to the upper chromosphere. Even if it did, the most optimistic estimate of the energy released through chromospheric reconnection is barely sufficient to account for the coronal energy losses.

Further, dynamical changes accompanying reconnection between uni- and multipolar fields are seen neither in the He i data nor in narrowband movies of the H alpha line core. We conclude that the hypothesis must be rejected. Bright chromospheric, transition region, and coronal loop plasmas must be heated by mechanisms involving unipolar fields.