RELATIVE BRIGHTNESS OF THE O+(2D-2P) DOUBLETS IN LOW-ENERGY AURORAE

Whiter, Daniel; Lanchester, B. S.; Gustavsson, B.; Jallo, N. I. B.; Jokiaho, O.; Ivchenko, Nickolay; Dahlgren, Hanna

doi:10.1088/0004-637x/797/1/64

Cited by 9 publications

(11 citation statements)

References 25 publications

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“…The relative brightness of the 732.0 nm and 733.0 nm emissions depends on the relative population of the two 2 P states, which was recently investigated in detail by Whiter et al [], who found that the brightness ratio in aurora will depend on the neutral temperature in the ionosphere. The discovery opens up the opportunity for a new spectral method to estimate the neutral temperatures and its variations in the auroral region.…”

Section: Technique To Estimate Electric Fields From Optical Measuremementioning

confidence: 99%

Electrodynamics and energy characteristics of aurora at high resolution by optical methods

et al. 2016

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Technological advances leading to improved sensitivity of optical detectors have revealed that aurora contains a richness of dynamic and thin filamentary structures, but the source of the structured emissions is not fully understood. In addition, high‐resolution radar data have indicated that thin auroral arcs can be correlated with highly varying and large electric fields, but the detailed picture of the electrodynamics of auroral filaments is yet incomplete. The Auroral Structure and Kinetics (ASK) instrument is a state‐of‐the‐art ground‐based instrument designed to investigate these smallest auroral features at very high spatial and temporal resolution, by using three electron multiplying CCDs in parallel for three different narrow spectral regions. ASK is specifically designed to utilize a new optical technique to determine the ionospheric electric fields. By imaging the long‐lived O+ line at 732 nm, the plasma flow in the region can be traced, and since the plasma motion is controlled by the electric field, the field strength and direction can be estimated at unprecedented resolution. The method is a powerful tool to investigate the detailed electrodynamics and current systems around the thin auroral filaments. The two other ASK cameras provide information on the precipitation by imaging prompt emissions, and the emission brightness ratio of the two emissions, together with ion chemistry modeling, is used to give information on the energy and energy flux of the precipitating electrons. In this paper, we discuss these measuring techniques and give a few examples of how they are used to reveal the nature and source of fine‐scale structuring in the aurora.

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Section: Technique To Estimate Electric Fields From Optical Measuremementioning

confidence: 99%

Electrodynamics and energy characteristics of aurora at high resolution by optical methods

et al. 2016

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“…Therefore, in future we intend to modify our spectral fitting method to take into account the possible presence of N 2 emission at different temperatures in a single spectrum. Whiter et al (2014) showed that the ratio of the two O + doublets observed by HiTIES at 732 and 733 nm can be used as a measure of the neutral temperature in the F-region ionosphere. We can determine this ratio, R O + , with a distribution of relative errors of less than 5 % when the peak of the 732 nm O + doublet is greater than 6 times the background emission.…”

Section: Discussionmentioning

confidence: 99%

Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Chadney¹,

Whiter²

2018

Preprint

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Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725–740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES), located on Svalbard. In this paper, we describe our new method and show the results of Monte-Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method as well as provide an indication of uncertainties on the retrieval of each atmospheric parameter.

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“…During times of high‐energy particle precipitation, the dominant auroral emission in this wavelength region comes from vibrational transitions of the N 2 1PG band ( B 3 Π ‐ A 3 Σ). Other emissions include the OH(8–3) band (airglow), two auroral O + doublets at wavelengths λ = 732.01 and 731.90 nm and λ = 733.08 and 732.97 nm (Whiter et al, ), and a small contribution from O

_{2}^{+}

1N auroral emission (

b^{4} {normal∑}_{g}^{-}

‐ a 4 Π u ).…”

Section: Observationsmentioning

confidence: 99%

High‐Resolution Optical Observations of Neutral Heating Associated With the Electrodynamics of an Auroral Arc

et al. 2019

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We present results that indicate the existence of two distinct neutral heating processes associated with a discrete auroral arc over Svalbard. Within the order of seconds, the thermospheric temperature profile displays a significant response to the arc on spatial scales smaller than 10 km. It is suggested that both heating signatures are associated with the electrodynamic system responsible for the formation of the arc. Pedersen currents produce a temperature increase of approximately 100 K, observed at altitudes between 80 and 160 kilometres, directly adjacent to the arc structure and on its poleward edge only. In contrast, field-aligned currents produce a variable temperature increase, of approximately 50 K, which is observed within the arc itself and constrained to a narrow altitude range between 90 and 110 km. By utilizing a range of observations and new analysis methods we are able to measure the atmospheric neutral temperature profile, over auroral altitudes, at unprecedented temporal and spatial scales. The High Throughput Imaging Echelle Spectrograph records high-resolution emission spectra of the aurora, which are then fitted with synthetic N 2 spectra, generated with modeled N 2 volume emission rate profiles and a library of trial temperature profiles. The N 2 volume emission rate profiles are retrieved from the Southampton ionospheric model using precipitating particle energies and fluxes obtained from Auroral Structure and Kinetics and the EISCAT Svalbard Radar. The application of this technique allows us to produce a time series of neutral temperature profiles and measure the localized heating of the neutral atmosphere resulting from the electrodynamics of the arc. Key Points: • Development of a new observing technique allows for the measurement of neutral temperature profiles during auroral events at an unprecedented temporal resolution • A case study of a morning sector auroral arc over Svalbard reveals a region of significant Joule heating on its poleward edge • Evidence of a separate Ohmic heating signature embedded within the arc and associated with strong field aligned currents Supporting Information: • Supporting Information S1

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RELATIVE BRIGHTNESS OF THE O⁺(²D-²P) DOUBLETS IN LOW-ENERGY AURORAE

Cited by 9 publications

References 25 publications

Electrodynamics and energy characteristics of aurora at high resolution by optical methods

Electrodynamics and energy characteristics of aurora at high resolution by optical methods

Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

High‐Resolution Optical Observations of Neutral Heating Associated With the Electrodynamics of an Auroral Arc

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