Poleward progressing quasi-periodic disturbances at cusp latitudes: The role of wave processes,
Pilipenko, V. A., E. N. Fedorov, M. J. Engebretson, V. O. Papitashvili, J. Watermann (2000),
J. Geophys. Res., 105, NA12 p. 27,569–27,588,
10.1029/2000JA900076.