The auroral distribution and its mapping according to substorm phase

• Published in: Journal of atmospheric and terrestrial physics Vol. 55; no. 14; pp. 1741 - 1762
• Main Authors: Elphinstone, R.D., Murphree, J.S., Hearn, D.J., Heikkila, W., Henderson, M.G., Cogger, L.L., Sandahl, I.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: London Elsevier B.V 01.12.1993; Pergamon Press
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Interaction between ionosphere and magnetosphere; Physics of the ionosphere; Auroral oval; Morphology; Magnetospheric substorm
• ISSN: 0021-9169
• DOI: 10.1016/0021-9169(93)90142-L

An attempt is made to reconcile two competing views as to where the auroral distribution maps from in the magnetosphere. The structure of the aurora is shown to have two distinctive parts which vary according to the magnetic activity. The low latitude portion of the structured distribution may be a near-Earth central plasma sheet phenomenon while the high latitude portion is linked more closely to boundary layer processes. During quiet times, the polar arcs may be the ionospheric signature of a source region in the deep tail low latitude boundary layer/cool plasma sheet. The structured portion of the ‘oval’ has a dominantly near-Earth nightside source and corresponds to an overlap region between isotropic 1–10 keV electrons and 0.1–1 keV structured electrons. The ionospheric local time sector between 13 and 18 MLT is the meeting point between the dayside boundary layer source region and this near-Earth nightside source. Late in the substorm expansion phase and/or start of the substorm recovery phase, the nightside magnetospheric boundaries (both the low latitude and Plasma Sheet Boundary Layers) begin to play an increasingly important role, resulting in an auroral distribution specific to the substorm recovery phase. These auroral observations provide a means of inferring important information concerning magnetospheric topology.