“…Then, in the stable case, the field lines oscillate mainly in the direction along the axis of the arcade, b r b y , while in the unstable case, they are displaced mainly in the radial direction, b r b y . This agrees with results obtained in earlier publications (Agapitov, Cheremnykh, and Parnowski, 2008;Mazur, Fedorov, and Pilipenko, 2012). Thus, the corrugation instability of an arcade distorts its boundary in the radial, i.e.…”