Dayside auroral activity and magnetospheric boundary layer phenomena

Four cases of dayside optical auroral observations and related parameters such as ground and satellite magnetometer data, reflecting ionospheric and Birkeland currents, ion and electron precipitation, and ionospheric ion drift are presented in order to illustrate different aspects of the dayside auroral electrodynamics that are pertinent to the problem of momentum transfer to the ionosphere. The case studies include (1) cusp/cleft auroral distinction; (2) coordinated ground-based and satellite observations of magnetospheric plasma populations; (3) midday auroral breakup sequence; and (4) periodic auroral forms in the 14-15 MLT sector and associated Pc5 magnetic pulsations at lower latitudes. The similarities between the dayside breakup events and the auroral activity in the evening sector during substorms indicate that similar processes may be involved.