Optical observations of flickering aurora and its spatiotemporal characteristics

Gustavsson, B.; Lunde, J.E.; Blixt, E. M.

doi:10.1029/2008ja013515

Cited by 12 publications

(22 citation statements)

References 20 publications

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“…[35] Our observation results are consistent with the model that interfering EMIC waves resonantly interact to electrons at several thousand kilometers altitude, as indicated by Sakanoi et al [2005] and Gustavsson et al [2008]. The flickering stripes shown in Figure 6 are naturally expected from the interference of plane waves propagating in closely parallel directions.…”

Section: Discussionsupporting

confidence: 79%

“…There might be several waves in the flickering region as seen in the flickering stripes ( Figure 6). In section 5, we assume the model that EMIC waves cause the modulation of the flickering aurora as supported in previous study [e.g., Sakanoi et al, 2005;Gustavsson et al, 2008], and estimate the relation between w and k based on the imaging observations of flickering aurora.…”

Section: Discussionmentioning

confidence: 99%

“…Holmes et al [2005aHolmes et al [ , 2005b and Whiter et al [2008] found the smallest scale size for the flickering spots of less than 1 km. These spots are sometimes observed associated with both rapid drifting and rotating features [Kunitake and Oguti, 1984;Gustavsson et al, 2008]. The typical amplitude of the periodic luminosity modulation has been reported as 10-20% of the total intensity of background auroral arcs [Kunitake and Oguti, 1984;Sakanoi and Fukunishi, 2004;Gustavsson et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

“…The horizontal phase velocity w/k of a flickering pattern at angular frequency w corresponds to the high-frequency component. Gustavsson et al [2008] also discussed the beat pattern in detail.…”

Section: Event Analysismentioning

confidence: 99%

“…Gustavsson et al [2008] showed the twodimensional calculation based on the Temerin-Sakanoi model, and they indicated that flickering spots with rotating features can also be explained by the interference of three or more EMIC waves propagating with some different angles. In fact, even the finest structures of flickering aurora with less than 1 km scale as reported by Whiter et al [2008] and Holmes et al [2005aHolmes et al [ , 2005b are consistent with the model of interference among several EMIC waves.…”

Section: Introductionmentioning

confidence: 99%

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Spatial-temporal characteristics of flickering aurora as seen by high-speed EMCCD imaging observations

et al. 2011

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[1] We conducted high-speed imaging observations of flickering aurora at 100 Hz sampling rate using electron multiplying charge-coupled device in Alaska during 2009-2010 winter season. We detected various types of flickering aurora, including drifting and rotating features at a frequency below 15 Hz. We identified, for the first time, flickering stripes and some other unusual flickering events at frequency of higher than 20 Hz on the imaging observations. A dispersion relation derived from a statistical analysis of observed images is compared with the theoretical dispersion curve of O + electromagnetic ion cyclotron (EMIC) waves. The frequencies and spatial scales calculated from a coherence/phase analysis based on an interference theory are consistent with the wave dispersion relation derived from the statistical analysis, suggesting that the obtained results are essentially consistent with the scenario that the interference of EMIC waves produces the observed dispersion relation of flickering aurora. Furthermore, flickering frequencies higher than 20 Hz are confirmed from our observations, which are higher than expected frequency of O + EMIC waves at altitudes of several thousand kilometers. We therefore suggest that high-frequency waves such as He + and H + EMIC waves may also contribute to produce a significant fraction of flickering aurora.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Event Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial-temporal characteristics of flickering aurora as seen by high-speed EMCCD imaging observations

et al. 2011

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Substructures with luminosity modulation and horizontal oscillation in pulsating patch: Principal component analysis application to pulsating aurora

et al. 2016

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We observed a mesoscale aurora (100 km × 100 km) with patchy structure and equatorward propagation at Poker Flat Research Range on 1 December 2011. Fast Fourier transform (FFT) analysis revealed that this pulsating patch clearly exhibited temporal variations that can be categorized into two types: on‐off pulsation (7.8–10 s) with large amplitudes and luminosity modulations excited during on phase with a frequency of about 3.0 Hz. In addition, we applied principal component analysis (PCA) to time series image data of the pulsating aurora for the first time. Time coefficients were estimated by PCA for the whole patch and the substructures were consistent with those obtained from the FFT analysis, and therefore, we concluded that PCA is capable of decomposing several structures that have different coherent spatiotemporal characteristics. Another new insight in this study is that the rapid variations were highly localized; they were excited in only the substructures embedded in the whole structure. Moreover, the whole patch propagated equatorward because of E × B drift of cold plasma, while the substructures did not show such systematic propagation but rather forward‐backward oscillations. The horizontal scale of the substructures was estimated to be no smaller than 410 km at the magnetic equator, which is comparable to that of the wave packet structure of a whistler mode chorus perpendicular to the field line. We suggest that the apparent horizontal oscillation of the substructures is associated with field‐aligned propagations of the whistler mode chorus in a duct.

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First evidence of patchy flickering aurora modulated by multi‐ion electromagnetic ion cyclotron waves

Fukuda

Kataoka

Uchida

et al. 2017

Geophysical Research Letters

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Electromagnetic ion cyclotron (EMIC) waves, one of the possible origins of flickering aurora, have been thought to modulate the electron flux at a few thousand kilometers. In fact, flickering aurora with a frequency range of 3–15 Hz has often been identified by ground‐based optical observations and has been interpreted to be caused by O+‐band EMIC waves. However, extant research to date has not identified possible signatures of H+‐band EMIC waves due to technical limitations of ground‐based high‐speed imagers. The present study shows the first evidence that patchy flickering aurora could be modulated by H+‐band EMIC waves, based on the data obtained from imaging observations at 160 frames per second. The sporadic appearance of the flickering aurora in the frequency range of 50–80 Hz coexisted with typical flickering auroras of approximately 10 Hz. These results are consistent with the hypothesis that flickering auroras are generated by multi‐ion EMIC waves.

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Optical observations of flickering aurora and its spatiotemporal characteristics

Cited by 12 publications

References 20 publications

Spatial-temporal characteristics of flickering aurora as seen by high-speed EMCCD imaging observations

Spatial-temporal characteristics of flickering aurora as seen by high-speed EMCCD imaging observations

Substructures with luminosity modulation and horizontal oscillation in pulsating patch: Principal component analysis application to pulsating aurora

First evidence of patchy flickering aurora modulated by multi‐ion electromagnetic ion cyclotron waves

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