On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

Liang, J.; Donovan, E.; Jackel, B. J.; Spanswick, E.; Gillies, M. F.

doi:10.1002/2016ja022901

Cited by 38 publications

(65 citation statements)

References 43 publications

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“…In particularly, based upon 630 nm auroral observations Liang et al . [] proposed the possibility of the occasional occurrence of pulsating auroral events consisting of soft electron precipitation on order of hundreds of eV, which is known as capable of producing significant heating effects on F region electrons. Oyama et al .…”

Section: Discussionmentioning

confidence: 99%

“…The scale height 25 km is estimated from the altitudinal decay of Pederson conductivity, calculated from Liang et al . [] model and the auroral precipitation prescribed by equation to be introduced later in this section. In the upper F region, the altitudinal range of our main interest, the perpendicular currents are negligibly small, yielding

j_{true/ true/}^{th} true/ B \approx

const.…”

Section: Theory and Model Simulation Of Ionospheric Electron Heatingmentioning

confidence: 99%

“…N e , N i , and Q e (secondary electron heating) profiles are adjusted at each iteration step according to the newly computed T e and T i profiles using Liang et al . [] model. The altitudinal grid is 2 km for z > 180 km and 1 km for z < 180 km in our numerical scheme.…”

Section: Theory and Model Simulation Of Ionospheric Electron Heatingmentioning

confidence: 99%

“…We then adopt the IRI2012 T e and T i profiles as the initial guess (except for the boundary values which are treated differently according to the Journal of Geophysical Research: Space Physics 10.1002/2017JA024127 boundary conditions) and use a Newton relaxation algorithm [Deulfhard, 2004] to reduce residues and iterate toward a convergent solution. N e , N i , and Q e (secondary electron heating) profiles are adjusted at each iteration step according to the newly computed T e and T i profiles using Liang et al [2016] model. The altitudinal grid is 2 km for z > 180 km and 1 km for z < 180 km in our numerical scheme.…”

Section: Referring Tomentioning

confidence: 99%

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Ionospheric electron heating associated with pulsating auroras: A Swarm survey and model simulation

et al. 2017

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In this paper we report a study on the plasma signatures (electron temperature, plasma density, and field‐aligned current) of patchy pulsating auroras in the upper F region ionosphere using Swarm satellite data. Via a survey of 38 patch crossing events, we repeatedly identify a strong electron temperature enhancement associated with the pulsating aurora. On average, the electron temperature at Swarm satellite altitudes (~460 km) increases from ~2200 K at subauroral latitudes to a peak of ~3000 K within the pulsating auroral patch. This indicates that pulsating auroras may act as an important heating source for the nightside ionosphere. On the other hand, no well‐defined trend of plasma density variations associated with pulsating auroras is identified at Swarm altitudes. The field‐aligned currents within the pulsating aurora patch are mostly upward, with mean magnitudes on order of ~1 μA/m2. We then perform a numerical simulation to explore the potential mechanisms underlying the strong electron heating associated with the pulsating aurora. Via simulations we find that to account for the realistic electron temperature observation in a major portion of our events, pulsating auroras are likely accompanied by substantial magnetospheric heat fluxes around the order of ~1010 eV/cm2. We propose that such magnetospheric heat fluxes may be pertinent to one long‐hypothesized feature of pulsating auroras, namely, the coexistence of an enhanced low‐energy plasma population in magnetic flux tubes threading the pulsating aurora, in addition to the energetic electron precipitation. Via a Swarm survey we repeatedly find a strong electron temperature enhancement associated with the pulsating aurora The field‐aligned currents within pulsating auroras are moderately upward, with mean magnitudes on the order of ~1e−6 A/m2 To explain the observed electron heating, pulsating auroras are likely accompanied by magnetospheric heat fluxes around ~1E+10 eV/cm2/s.

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Section: Discussionmentioning

confidence: 99%

j_{true/ true/}^{th} true/ B \approx

const.…”

Section: Theory and Model Simulation Of Ionospheric Electron Heatingmentioning

confidence: 99%

Section: Theory and Model Simulation Of Ionospheric Electron Heatingmentioning

confidence: 99%

Section: Referring Tomentioning

confidence: 99%

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Ionospheric electron heating associated with pulsating auroras: A Swarm survey and model simulation

et al. 2017

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“…REGO is a 630-nm red-line imager (Liang et al, 2016). Major optical instruments used in this study include the multiwavelength all-sky-imagers (ASIs) of the Athabasca University Geophysical Observatory (AUGSO) at Athabasca (54.60°N, 113.64°W), the Redline Emission Geospace Observatory (REGO), the Four-Eight-Six-One (FESO) photometer and the Transition Region Explorer Spectrograph (TRSp).…”

Section: Observationsmentioning

confidence: 99%

Optical Spectra and Emission Altitudes of Double‐Layer STEVE: A Case Study

Liang

Donovan

Connors

et al. 2019

Geophysical Research Letters

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We report an event study of STEVE on 17 July 2018, with focus on the optical spectra and emission altitudes of STEVE. We find that the STEVE comprises two traces, one at a higher elevation angle and the other at a lower elevation angle. The two traces merge into one when viewed near the zenith. Spectrograph measurements show that both STEVE traces are characterized by enhancements over broadband wavelengths, that is, an airglow continuum, but they differ in their red-line (630 nm) component: The higher-elevation STEVE contains substantial red-line enhancement over background, while the lower-elevation STEVE does not. Based upon triangulation analyses using multiple optical instruments, we evaluate that the two STEVE traces are likely emitted from distinctly different altitudes: The higher-elevation STEVE comes from~250-km altitude, while the lower-elevation one is from ≤150-km altitude. Our results impose implications and constraints on the possible underlying mechanisms of STEVE. Plain Language SummaryThe recently discovered STEVE nightglow is active at times of auroral activity but does not seem to be an aurora. It is located at lower latitudes than the usual aurora, and as photographed on the citizen science cameras which played a large role in drawing attention to it, it has a different color. In this study, using a combination of scientific optical instruments, especially the spectrograph recently deployed at Lucky Lake, Canada, by the University of Calgary, we investigate the optical spectral properties of STEVE and their emission altitudes. Two major spectral (color) components of STEVE are identified. One is characterized by a broadband enhancement over the entire visible wavelength range, contributing to the apparently "whitish" color of the STEVE, and the other is contributed by oxygen airglow concentrated at 630 nm, adding a "reddish" tint to the STEVE. In the event occurring on 17 July 2018, the STEVE is found to comprise two emission structures originating from different altitudes, one at~250 km and the other at ≤150-km altitude. Both STEVE structures contain the white component but only the higher-altitude one shows a substantial red component. That red color is the same red as seen in auroras that come from high altitudes in the atmosphere, while the mechanism of the white component remains to be explored.

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A Comparative Study of Spectral Auroral Intensity Predictions From Multiple Electron Transport Models

et al. 2018

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It is important to routinely examine and update models used to predict auroral emissions resulting from precipitating electrons in Earth's magnetotail. These models are commonly used to invert spectral auroral ground‐based images to infer characteristics about incident electron populations when in situ measurements are unavailable. In this work, we examine and compare auroral emission intensities predicted by three commonly used electron transport models using varying electron population characteristics. We then compare model predictions to same‐volume in situ electron measurements and ground‐based imaging to qualitatively examine modeling prediction error. Initial comparisons showed differences in predictions by the GLobal airglOW (GLOW) model and the other transport models examined. Chemical reaction rates and radiative rates in GLOW were updated using recent publications, and predictions showed better agreement with the other models and the same‐volume data, stressing that these rates are important to consider when modeling auroral processes. Predictions by each model exhibit similar behavior for varying atmospheric constants, energies, and energy fluxes. Same‐volume electron data and images are highly correlated with predictions by each model, showing that these models can be used to accurately derive electron characteristics and ionospheric parameters based solely on multispectral optical imaging data.

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On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

Cited by 38 publications

References 43 publications

Ionospheric electron heating associated with pulsating auroras: A Swarm survey and model simulation

Ionospheric electron heating associated with pulsating auroras: A Swarm survey and model simulation

Optical Spectra and Emission Altitudes of Double‐Layer STEVE: A Case Study

A Comparative Study of Spectral Auroral Intensity Predictions From Multiple Electron Transport Models

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