The auroral luminosity structure in the high‐latitude upper atmosphere: Its dynamics and relationship to the large‐scale structure of the Earth's magnetosphere

Abstract

The concept of the auroral oval was proposed independently by Feldstein and by Khorosheva in the early 1960's, and it has since been widely used as a reference frame for the organization of high‐latitude optical, particle, and ionospheric data. More recently, different structural regions associated with the oval have been distinguished, and these have been identified with different magnetospheric regions by different workers. The net result is an inconsistent set of nomenclature and relationships. The literature of this development is reviewed in detail, and an interpretation and terminology that is consistent, in the opinion of the authors at least, are proposed. It is hoped that this proposal will serve as a useful basis for further discussion on the ordering of auroral phenomena in relation to the magnetosphere.

Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles

“…As regards the main point, our ®ndings are in good agreement with the view of Feldstein and Galperin (1985). They concluded (Feldstein and Galperin, 1985, p.251) that``the separating boundary between the di use and discrete auroras ... is the stable trapping boundary of >40-keV electrons''.…”

“…It should be noted that in fact the weak di use aurora can be observed across the whole auroral zone until the polar-cap boundary (e.g. Feldstein and Galperin, 1985), but the most intense luminosity is expected to be mapped to the region of the large loss cone.…”

“…The discussion on the sources of auroral precipitation has a long history (see e.g. the reviews by Feldstein and Galperin, 1985;Galperin and Feldstein, 1991;Feldstein and Elphinstone, 1992;Weiss et al, 1992;Elphinstone et al, 1995;Newell et al, 1996). All authors generally agree that the source region of the di use aurora is the inner, near-Earth plasma sheet; it is the origin of the discrete auroras that is a main subject of discussion.…”

“…Another scheme, proposed by Feldstein and Galperin (1985) and Galperin and Feldstein (1991), placed the earthward edge of the discrete-arc source region deep into the inner magnetosphere. They introduced the term`r emnant layer'' for the region between the plasmapause and inner edge of the electron plasma sheet and associated this region with the di use auroras.…”

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

“…The bombardment of the atmosphere by low energy electrons causes diffuse aurora which is located in the region near the equatorward edge of the auroral oval (Feldstein and Galperin, 1985;Horwitz et al, 1986). However, only a part of the low energy electrons with energies less than or equal to about 2-5 eV is mainly effective for producing ionization at F-region altitudes (Rees, 1964).…”