On a source of Alfvén waves heating the solar corona

Studies of the origin of coronal heating and acceleration of the solar wind invoke high-frequency Alfvén waves. Here we suggest a source for such waves associated with twisted magnetic loops emerging on the solar surface and reconnecting with the open field. We identify the loops with the ephemeral regions (small-scale bipoles) observed by ground-based instruments and by SOHO. To characterize the loops we employ the concept of a minimum energy state for topologically complex fields. Emerging loops release energy relaxing to the minimum state. Relaxation along the minimum state–due to a competition between footpoint twisting by photospheric motions and reconnections inside the loops– releases blinks of energy into the solar atmosphere. We estimate the power released and the range of wave frequencies.