Poleward moving auroral forms (PMAFs) revisited: Relationships with plasma convection, field-aligned currents, and the IMF B_y polarity

In a case study we probe the dependence on the polarity of the east-west (B_y) component of the IMF of the system of dayside auroral precipitation, plasma convection and field-aligned currents. The basic lesson is inferred from ground observations of the aurora in combination with data obtained from ground-based radars and spacecraft in polar orbit. A main emphasis is placed on contrasting the behavior of poleward moving auroral forms (PMAFs) occurring respectively in the prenoon and postnoon sectors, intercomparing these auroral transients and their associated plasma flow channels and Birkeland currents for both B_y polarities. The auroral phenomenon consists of a sequence of brightening events accompanied by pulsed ionospheric flows (PIFs). Each event is characterized by the successive activation of auroral forms located at progressively higher latitudes corresponding to the precipitation regimes called (i) boundary plasma sheet (BPS), (ii) low-latitude boundary layer (LLBL), and (iii) plasma mantle. For a given B_y polarity the dawn-dusk asymmetry of the solar wind-magnetosphere interconnection topology introduces a corresponding asymmetry in the PMAFs/prenoon versus PMAFs/postnoon.