Modelling N21P contamination in auroral O+ emissions

Spry, J.D.; Jokiaho, O.; Lanchester, B. S.; Whiter, Daniel

doi:10.1016/j.jastp.2013.10.013

Cited by 6 publications

(7 citation statements)

References 12 publications

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“…The modeled transmission ratio is derived from synthetic N 2 spectra. More information on this method to remove the contamination from the O + data is given in Spry et al [, and references therein]. For any such detailed spectral analysis it is important to keep the filter temperature constant, as the transmission curve is temperature dependent.…”

Section: Technique To Estimate Electric Fields From Optical Measuremementioning

confidence: 99%

“…A different method to estimate the contamination of the O + emissions was presented by Spry et al [], based on imager data from ASK in combination with modeled synthetic spectra of the N 2 1PG (5,3) emission band. Unlike the methods described above, variations of the rotational and vibrational temperature of molecular nitrogen can now be taken into account.…”

Section: Technique To Estimate Electric Fields From Optical Measuremementioning

confidence: 99%

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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%

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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“…However, 95 there is some contamination from the (5,3) band of the N 2 1PG band system and hydroxyl airglow. The N 2 contamination is removed using the method of Spry et al (2014), and the hydroxyl contamination is removed by background subtraction.…”

Section: Introductionmentioning

confidence: 99%

Horizontal electric fields from flow of auroral O+(2P) ions at sub-second resolution

Tuttle¹,

Lanchester²,

Gustavsson³

et al. 2020

Preprint

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Abstract. Electric fields are a ubiquitous feature of the ionosphere and are intimately linked with aurora through particle precipitation and field-aligned currents. We present a unique method to estimate ionospheric electric fields beside a dynamic auroral feature by solving the continuity equation for the metastable O+(2P) ions, which emit as they move under the influence of electric fields during their 5 s lifetime. Simultaneous measurements of emission at 732.0 nm (from the O+(2P) ions), and prompt emissions at 673.0 nm (N2) and 777.4 nm (O), all at high spatial (100 m) and temporal (0.05 s) resolution, are used in the solution of the continuity equation, which gives the dynamic changes of the O+ ion population at all heights in a 3D volume close to the magnetic zenith. Perspective effects are taken into account by a new geometric method, which is based on an accurate estimate of the magnetic zenith position. The emissions resulting from the metastable ions are converted to brightness images by projecting onto the plane of the ground, which are compared with the measured images. The flow velocity of the ions is a free parameter in the solution of the continuity equation; the value that minimizes the difference between the modelled and observed images is the extracted flow velocity at each time step. We demonstrate the method with an example event during the passage of a brightening arc feature, lasting about 10 s, in which the inferred electric fields vary between 20 and 120 mV m−1. These inferred electric fields are compared with SuperDARN measurements, which have an average value of 30 mV m−1. An excellent agreement is found in magnitude and direction of the background electric field; an increase in magnitude during the brightening of the arc feature supports theories of small scale auroral arc formation and electrodynamics.

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“…However, there is some contamination from the (5,3) band of the N 2 1PG band system and hydroxyl airglow. The N 2 contamination is removed using the method of Spry et al (2014), and the hydroxyl contamination is removed by background subtraction.…”

Section: Introductionmentioning

confidence: 99%

Horizontal electric fields from flow of auroral O+(2P) ions at sub-second temporal resolution

et al. 2020

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Abstract. Electric fields are a ubiquitous feature of the ionosphere and are intimately linked with aurora through particle precipitation and field-aligned currents. They exhibit order-of-magnitude changes on temporal and spatial scales of seconds and kilometres respectively which are not easy to measure; knowing their true magnitude and temporal variability is important for a theoretical understanding of auroral processes. We present a unique method to estimate ionospheric electric fields in the region close to (kilometre scale) a dynamic auroral arc by solving the continuity equation for the metastable O+(2P) ions, which emit as they move under the influence of electric fields during their 5 s lifetime. The main advantage of this optical method is the increase in temporal resolution over other methods such as ground-based radars. Simultaneous measurements of emission at 732.0 nm (from the O+(2P) ions) and prompt emissions at 673.0 nm (N2) and 777.4 nm (O), all at high spatial (100 m) and temporal (0.05 s) resolution, are used in the solution of the continuity equation, which gives the dynamic changes of the O+ ion population at all heights in a 3D volume close to the magnetic zenith. Perspective effects are taken into account by a new geometric method, which is based on an accurate estimate of the magnetic zenith position. The emissions resulting from the metastable ions are converted to brightness images by projecting them onto the plane of the ground, and the projected images are then compared with the measured images. The flow velocity of the ions is a free parameter in the solution of the continuity equation; the value that minimises the difference between the modelled and observed images is the extracted flow velocity at each time step. We demonstrate the method with an example event during the passage of a brightening arc feature, lasting about 10 s, in which the inferred electric fields vary between 20 and 120 mV m−1. These inferred electric fields are compared with SuperDARN measurements, which have an average value of 30 mV m−1. An excellent agreement is found in the magnitude and direction of the background electric field; an increase in magnitude during the brightening of the arc feature supports theories of small-scale auroral arc formation and electrodynamics.

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Modelling N21P contamination in auroral O+ emissions

Cited by 6 publications

References 12 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

Horizontal electric fields from flow of auroral O<sup>+</sup>(<sup>2</sup>P) ions at sub-second resolution

Horizontal electric fields from flow of auroral O<sup>+</sup>(<sup>2</sup>P) ions at sub-second temporal resolution

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Modelling N21P contamination in auroral O+ emissions

Cited by 6 publications

References 12 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

Horizontal electric fields from flow of auroral O&lt;sup&gt;+&lt;/sup&gt;(&lt;sup&gt;2&lt;/sup&gt;P) ions at sub-second resolution

Horizontal electric fields from flow of auroral O&lt;sup&gt;+&lt;/sup&gt;(&lt;sup&gt;2&lt;/sup&gt;P) ions at sub-second temporal resolution

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Horizontal electric fields from flow of auroral O<sup>+</sup>(<sup>2</sup>P) ions at sub-second resolution

Horizontal electric fields from flow of auroral O<sup>+</sup>(<sup>2</sup>P) ions at sub-second temporal resolution