Use of FUV auroral emissions as diagnostic indicators
- Univ. of Alabama, Huntsville, AL (United States)
- NASA Marshall Space Flight Center, Huntsville, AL (United States)
In an earlier study the authors modeled selected FUV auroral emissions (O I (1356 [angstrom]), N[sub 2] Lyman-Birge-Hopfield (LBH) (1464 [angstrom]), and LBH (1838 [angstrom])) to examine the sensitivity of these emissions and their ratios to likely changes in the neutral atmosphere. In this paper they extent that study to examine the dependence of these same emissions and their ratios on the shape of the energy distribution of the auroral electrons. In particular, they wish to determine whether changes in energy spectra might interfere with their determination of the characteristic energy. Modeled column-integrated emissions show relatively small (<30%) dependences on the shape and width of the incident energy spectrum, provided the average energy and total energy flux of the energy distribution are held constant. Long-wavelength FUV emissions, which are relatively unaffected by O[sub 2] absorption losses, exhibit virtually no dependence on the shape of the incident energy distribution. Changes in ratios of FUV short- to long-wavelength emissions as a function of characteristic energy are much larger than those due to changes in energy distribution. As a result, the determination of characteristic energy using these emission ratios is relatively unambiguous. They also examine the relative intensities of the aurora and the dayglow for various conditions. The intensities of modeled FUV auroral emissions relative to the dayglow emissions are presented as a function of solar zenith angle and incident energy flux. Under certain conditions (energy flux [le] 1 erg cm[sup [minus]2] s[sup [minus]1] and solar zenith angle [le]50[degrees]) the dayglow will be the limiting factor in the detection of weak auroras. 19 refs., 10 figs., 1 tab.
- OSTI ID:
- 6701411
- Journal Information:
- Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 99:A1; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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