The Auroral Turbulence II (AT2) sounding rocket carried three payloads into the auroral ionosphere where they crossed several arc structures. At the border of an auroral arc a quasiperiodic structure was observed by the magnetic and electric field instruments as well as by the particle detectors. The variations were temporal oscillations, but existed only in a narrow (≈7 km) region transverse to the arc, with a correlation length along the arc of at least several km. The relation between the electric and magnetic field amplitude indicates the Alfv¿nic nature of the variations. Field aligned electron precipitation is correlated to the field variations. The narrow band nature of the oscillations and frequency around 0.6 Hz is consistent with waves confined in the ionospheric Alfv¿n resonator. ¿ 1999 American Geophysical Union