Aurorae and the Large-Scale Structure of the Magnetosphere

Abstract

An attempt is made to construct a road map for translating various plasma domains in the magnetosphere to their counterparts in the auroral ionosphere. Results of previous work have allowed much to be inferred about where in the magnetosphere auroral processes are taking place. The main auroral oval appears to be associated with magnetospheric processes well separated from boundary layer processes with the exception of the dayside sector between about 8 and 16 MLT. This sector is apparently dominated by sources in the dayside boundary layer and by the region where the nightside cross-tail current intersects the boundary layer regions. The division between the stably trapped particles and isotropic distributions probably coincides with the most equatorward discrete arc system involved with the substorm onset. Thus the diffuse aurora equatorward of the discrete aurora would be a ring current related phenomena and the nightside discrete aurora would originate dominantly from the central plasma sheet. During magnetically active conditions the outer edge of the central plasma sheet plays a more important role in the production of the discrete aurora. Diffuse aurora poleward of the discrete system is probably linked to velocity dispersed ion signatures seen in the low altitude ionosphere. © 1992, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.