Evaluation of auroral 5577- angstrom excitation processes using Intercosmos Bulgaria 1300 satellite measurements

Journal Article · Wed Apr 01 04:00:00 EST 1987 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA092iA04p03367· OSTI ID:5510444

Gerdjikova, M G; Shepherd, G G ^[1]

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1. Bulgarian Academy of Sciences, Sofia (Bulgaria)

Energy transfer from N{sub 2}(A{sup 3}{Sigma}{sub u}{sup +}) to O has been extensively studied as a mechanism for the production of 5577-{angstrom} emission in the aurora, but it has yet to be fully accepted as the dominant process. This reluctance arises from the three requirements that must be met. First, the correct absolute emission rate must be produced by this mechanism. Second, the lifetime of N{sub 2}(A) at auroral altitudes must be compatible with the observed time delays between the N{sub 2}{sup +} and 5577-{angstrom} emissions. Finally, the generally accepted high degree of covariance between the N{sub 2}{sup +} and 5577-{angstrom} emissions must be explained. This last aspect is the subject of this paper, in which the authors investigate this covariance in terms of spectral ratios. Measurements made from the Intercosmos Bulgaria 1300 satellite include the emission rate of the O I 5577-{angstrom} and N{sub 2}{sup +} 4278-{angstrom} emissions, and the flux of precipitating auroral electrons in the energy range 200 eV to 15 keV. Using the measured fluxes and atmospheric composition models, the emission rate ratio I(5577)/I(4278) for the N{sub 2}(A) energy transfer mechanism is calculated and compared with the observed values. The observed ratios vary mostly from 2 to 5, with a few values outside this range. They show that this variation arises from variations in the atomic oxygen concentration, partly as an altitude effect associated with changes in primary electron energy, but more dominantly as day-to-day variations that are larger than those indicated by the mass spectrometer/incoherent scatter 1983 model. Independent evidence that atomic oxygen is the source of the ratio variations is provided by correlated variations in the I(7320)/I(4278) ratio. The aspects of absolute emission rate and time delay are also reviewed, and it is concluded that the evidence is conclusively in favor of N{sub 2}(A) energy transfer as the dominant auroral mechanism.

• OSTI ID: 5510444
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 92:A4; 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
AIRGLOW
AURORAE
CHARGED-PARTICLE PRECIPITATION
CHEMICAL COMPOSITION
ELECTRON PRECIPITATION
ELEMENTS
EMISSION SPECTRA
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
NITROGEN
NONMETALS
OXYGEN
SATELLITES
SPECTRA
TIME DELAY
VARIATIONS