Magnetic field-aligned electric field acceleration and the characteristics of the optical aurora

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA092iA06p06163· OSTI ID:5962446

Christensen, A B; Lyons, L R; Hecht, J H; Sivjee, G G ^[1]; Meier, R R ^[2]; Strickland, D G ^[3]

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1. Aerospace Corp., Los Angeles, CA (United States)
2. Naval Research Lab., Washington DC (United States)
3. Computational Physics, Annandale, VA (United States)

The long-recognized association of brighter aurora with more deeply penetrating, and hence more energetic electrons is examined. Using the Knight (1973) relation between the magnetic field aligned current density j{sub parallel} and potential drop V{sub parallel}, derived from the theory of single particle motion in the presence of a magnetic field-aligned electric field, an approximate expression relating the energy flux Q of the precipitating electrons over discrete aurora and the mean particle energy E{sub M} is derived: Q(ergs/cm{sup 2}s) = kE{sub M}{sup {gamma}}, where 1.5 {le} {gamma} {le} 2 and k depends on the temperature and density of the plasma in the source region. This expression is used in conjuction with an auroral optical excitation and emission model to specify the dependence of the red (O I(630.0))/blue (N{sub 2}{sup +}(427.8)) ratio of auroral optical emissions on the brightness of the aurora. It is shown that the quantitative predictions of the discrete auroral theroy are in accord with observations of the aurora. Thus the often observed anticorrelation of the red/blue ratio with auroral brightness is consistent with the single-particle motion theory. It follows that in discrete auroral events where the theory is valid, the brightening of the aurora involves an increase in both the mean energy and the number flux of precipitating electrons.

• OSTI ID: 5962446
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 92:A6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
BRIGHTNESS
CHARGED-PARTICLE PRECIPITATION
CORRELATIONS
CURRENT DENSITY
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTROMAGNETIC RADIATION
ELECTRON PRECIPITATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
LEPTONS
MATHEMATICAL MODELS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLASMA DENSITY
RADIATIONS
TEMPERATURE DEPENDENCE
VISIBLE RADIATION