IMF <i>B_y</i>‐dependent plasma flow and Birkeland currents in the dayside magnetosphere: 1. Dynamics Explorer observations

Abstract

Plasma, magnetic‐field and dc electric‐field observations from Dynamics Explorers 1 and 2 are used to investigate the morphology of solar‐wind ion injection, Birkeland currents, and plasma convection in the morning sector for both positive and negative interplanetary magnetic field (IMF) B y components. The results of the study are used to construct a B y ‐dependent global convection model for southward IMF. A significant element of the model is the coexistence of three types of convection cells (“merging cells,” “viscous cells,” and “lobe cells”). This model can account for observations of a nearly stationary (in local time) convection “throat,” a sunward‐antisunward convection reversal zone at the polar‐cap boundary in both the morning and afternoon quadrants, the morphology of solar‐wind ion injection and transport in the mid‐altitude polar cusp, and the B y ‐dependent dawn‐dusk asymmetry of polar‐cap electron fluxes.