Poleward progressing quasiperiodic disturbances at cusp latitudes: The role of wave processes

Observations from various magnetometer networks, including Magnetomer Array for Cusp and Cleft Studies (MACCS), Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS), the Greenland Coastal Chain, and the U.S./ Russia Antarctic Array, made on January 5, 1995, show an event of very long period pulsations (30- to 40-min period) in the cusp region. Pulsations we re driven by quasiperiodic Interplanetary Magnetic Field (IMF) B-y, variati ons which were observed by the Wind spacecraft. Disturbances of this type a re commonly interpreted as poleward moving, east-west oriented ionospheric currents (e.g., intensification of the DPY current system), stimulated by r econnection processes at the dayside magnetopause. However, the temporal/sp atial, ground-based structure of such disturbances can better be described if this picture is augmented by the inclusion of transient wave processes, for example, distortions of the Alfven phase front, transmitting a disturba nce from an assumed reconnection region to the ionosphere. In general, this type of disturbance, which we suggest calling P(DPY)6 pulsations, is shown to be a manifestation of the modulation of the high-latitude ionosphere el ectrodynamics by a large-scale Alfven wave in the solar wind under favorabl e IMF orientation.