Dynamical auroral morphology in relation to ionospheric plasma convection and geomagnetic activity: Signatures of magnetopause X line dynamics and flux transfer events

Ground-based observations of auroral, geomagnetic, and radar signatures of solar wind-magnetosphere coupling modes are presented. Two different categories of ionospheric signatures are studied: (1) enhanced geomagnetic deflections and associated equatorward displacements of the cusp/cleft aurora and (2) a sequence of poleward moving amoral and geomagnetic events. It is suggested that signature 1 is mainly caused by directional. discontinuities in the interplanetary magnetic field changing the solar wind-magnetosphere coupling geometry and that signature 2 is caused by a recurring modulation of the reconnection rate at the dayside magnetopause (flux transfer events (FTEs)), during the period of strong coupling. The observed auroral and geomagnetic signatures are placed in the context Of plasma convection, as derived from magnetometers in Svalbard, Greenland, and Canada, and the European incoherent scatter (EISCAT) radar. A suggestion for an ionospheric current system explaining the sequence of poleward propagating events, i.e., the FTE signatures, is presented.