Coincident ultraviolet imager and energetic particle sensor observations of the continuous electron aurora

Eastes, R.; Daniell, R. E.; Leblanc, F.

doi:10.1016/s1364-6826(00)00078-x

Cited by 2 publications

(2 citation statements)

References 18 publications

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“…The idea of a two‐component optical auroral oval was first made by Elphinstone et al [1995a, 1995b] who referred to the double oval as a distribution that forms at the beginning of the substorm recovery phase. Carbury et al [2003] fitted a function consisting of a single Gaussian plus a second order polynomial [see also Eastes et al , 2000], although they pointed out that not all auroral latitude profiles could be fitted with a function based on a single Gaussian. Then Mende et al [2003] published an interesting study in which they performed a superposed epoch analysis of 91 substorms using data obtained from the IMAGE spacecraft.…”

Section: Discussionmentioning

confidence: 99%

Typical auroral substorm: A bifurcated oval

et al. 2008

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[1] Utilizing global auroral images obtained by Polar Visible Imaging System Earth Camera, we have analyzed the UV emissions from 116 auroral substorms. The events selected were fairly isolated and had to expand from a localized onset. It was found that essentially all auroral events fulfilling these simple criteria expand into the Akasofu (1964) bulge-type aurora. Averaged auroral emission patterns were compiled for 11 time steps of the substorm covering 20 min prior to the onset until well into the recovery phase. This compilation required a three-step normalization technique, one temporal based on the expansion time and two spatial, magnetic local time and latitude. These average patterns were then fit to either a single or double Gaussian distribution in latitude for each of 24 magnetic local times. On the basis of this analysis we made the following conclusions. The normalization technique is highly efficient in maintaining the key features in the individual auroral emission patterns, even though the individual events varied significantly in intensity, size, position, and lifetime. Thus our normalization results quantitatively validate the Akasofu (1964) assumption that key auroral features exist in the bulge-type auroral substorm. After the substorm onset the auroral oval becomes clearly bifurcated consisting of two components: the oval aurora in the latitude range of the preonset oval and expanding primarily eastward postmidnight, and the bulge aurora, which emerges out of the oval, expanding poleward and both east and west in MLT. The oval aurora decay faster than the bulge emissions indicating that the decays have separate time constants. Owing to the pronounced difference in the spatiotemporal behavior of the two auroral components we suggest that their sources are quasi-independent.

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Section: Discussionmentioning

confidence: 99%

Typical auroral substorm: A bifurcated oval

et al. 2008

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“…Fourth, the binned latitude profiles are then fit to functions having the form of a Gaussian plus a quadratic background: where λ is the magnetic latitude in degrees, the A i are coefficients of the fit, and F(λ) is the target intensity profile. Admittedly, not all profiles are well fit by , but previous authors have noted the similarity of auroral latitude profiles to Gaussian shapes [e.g., Eastes et al , 2000]. Most profiles are suggestive of such a form, and those which are not are removed by requiring that the fractional standard deviation of the fit be less than 0.20.…”

Section: Fits To Latitude Profilesmentioning

confidence: 99%

Auroral boundary correlations between UVI and DMSP

et al. 2003

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[1] Equatorward and poleward auroral boundaries from latitude profiles of Polar Ultraviolet Imager (UVI) auroral images were correlated with over 23,000 boundaries derived from 2 years of Defense Meteorological Satellite Program (DMSP) electron precipitation data. Latitude differences between DMSP and UVI boundaries were averaged into 1-hour and 3-hour sectors of magnetic local time (MLT). The statistical distributions of these differences generally peak near zero but have Gaussian-like shapes with widths of about 3°-4°in magnetic latitude. The mean values of these offsets exhibit systematic trends in MLT, with the largest disagreement near 05 MLT for the poleward boundaries and near noon for the equatorward boundaries. The mean offsets were fit to second-order harmonic expansions, which approximately ''calibrate'' image boundaries with respect to the precipitating electron boundaries. The harmonic fits suggest that the images can yield approximate precipitation boundaries for such purposes as estimating the area of the polar cap.

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Coincident ultraviolet imager and energetic particle sensor observations of the continuous electron aurora

Cited by 2 publications

References 18 publications

Typical auroral substorm: A bifurcated oval

Typical auroral substorm: A bifurcated oval

Auroral boundary correlations between UVI and DMSP

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