Optical tomography of the aurora and EISCAT

Frey, H. U.; Frey, S.; Lanchester, B. S.; Kosch, M.

doi:10.1007/s005850050700

Cited by 5 publications

(6 citation statements)

References 14 publications

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“…have been developed by using tomographic techniques [Frey et al, 1996[Frey et al, , 1998 Nygrdn et al, 1996;Gustavsson, 1998]. In all cases some a priori information is needed in order to regularize the inversion problem, which is otherwise ill-posed.…”

Section: Methods For Reconstructing the Volume Emission Ratesmentioning

confidence: 99%

Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

Janhunen¹

2001

J. Geophys. Res.

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Abstract. We present a method for reconstructing the precipitating electron flux from a set of multiwavelength digital all-sky auroral images. The method involves solving a large linear inversion problem, and it works for any number of all-sky imager stations and wavelengths. The idea in our method is to invert the energydependent precipitating electron flux directly and not the three-dimensional volume emission rate as an intermediate step. In this way, the inversion is automatically restricted to physical emission rate profiles. We show the effectiveness of the method in the all-sky camera case by simulated examples. The method is also applied to real data. The method is capable of correctly reconstructing not only auroral arc positions but also the precipitating electron energy and number fluxes, although not necessarily the full differential flux. A natural limitation is that arcs that are significantly off-zenith and are viewed sideways by only one all-sky camera station are smeared out. However, even for these arcs the average arc position and energy characteristics come out with reasonable accuracy.

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Section: Methods For Reconstructing the Volume Emission Ratesmentioning

confidence: 99%

Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

Janhunen¹

2001

J. Geophys. Res.

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“…Of significance are the recently observed asymmetries in auroral intensities between the northern and southern hemispheres [ Laundal and Østgaard , ]. Ground‐based and multiple‐aspect camera studies allow the determination and reconstruction of auroral structuring at continental and meso‐scale [ Donovan et al ., ; Frey et al ., ; Rees et al ., ] down to much smaller scales, such as curls and boundary undulations (tens of kilometers to hundreds of meters) [ Dahlgren et al ., ; Sandahl et al ., ]. Davis [] provides an accessible guide to auroral structures and their processes; a more recent review of the multiple scales present in auroral plasmas is given by Galperin [].…”

Section: Introductionmentioning

confidence: 99%

GPS phase scintillation associated with optical auroral emissions: First statistical results from the geographic South Pole

et al. 2013

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Ionospheric irregularities affect the propagation of Global Navigation Satellite System (GNSS) signals, causing radio scintillation. Particle precipitation from the magnetosphere into the ionosphere, following solar activity, is an important production mechanism for ionospheric irregularities. Particle precipitation also causes the aurorae. However, the correlation of aurorae and GNSS scintillation events is not well established in literature. This study examines optical auroral events during 2010–2011 and reports spatial and temporal correlations with Global Positioning System (GPS) L1 phase fluctuations using instrumentation located at South Pole Station. An all‐sky imager provides a measure of optical emission intensities ([OI] 557.7 nm and 630.0 nm) at auroral latitudes during the winter months. A collocated GPS antenna and scintillation receiver facilitates superimposition of auroral images and GPS signal measurements. Correlation statistics are produced by tracking emission intensities and GPS L1 σφ indices at E and F‐region heights. This is the first time that multi‐wavelength auroral images have been compared with scintillation measurements in this way. Correlation levels of up to 74% are observed during 2–3 hour periods of discrete arc structuring. Analysis revealed that higher values of emission intensity corresponded with elevated levels of σφ. The study has yielded the first statistical evidence supporting the previously assumed relationship between the aurorae and GPS signal propagation. The probability of scintillation‐induced GPS outages is of interest for commercial and safety‐critical operations at high latitudes. Results in this paper indicate that image databases of optical auroral emissions could be used to assess the likelihood of multiple satellite scintillation activity.

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“…Prior work in auroral tomography [5], [9], [10] has focused almost exclusively on mesoscale features of 10 4 m width recorded with typical sampling periods of order 1-30 seconds, with sensor baselines of 50-150 km. The peak auroral emission intensity typically lies in the altitude range of approximately 100-300 km.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of Fine-Scale Auroral Dynamics

Hirsch

Semeter

Zettergren

et al. 2016

IEEE Trans. Geosci. Remote Sensing

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Abstract-We present a feasibility study for a high frame rate, short baseline auroral tomographic imaging system useful for estimating parametric variations in the precipitating electron number flux spectrum of dynamic auroral events. Of particular interest are auroral substorms, characterized by spatial variations of order 100 m and temporal variations of order 10 ms. These scales are thought to be produced by dispersive Alfvén waves in the near-Earth magnetosphere. The auroral tomography system characterized in this paper reconstructs the auroral volume emission rate to estimate the characteristic energy and location in the direction perpendicular to the geomagnetic field of peak electron precipitation flux using a distributed network of precisely synchronized ground-based cameras. As the observing baseline decreases, the tomographic inverse problem becomes highly ill-conditioned; as the sampling rate increases, the signal-to-noise ratio degrades and synchronization requirements become increasingly critical. Our approach to these challenges uses a physics-based auroral model to regularize the poorlyobserved vertical dimension. Specifically, the vertical dimension is expanded in a low-dimensional basis consisting of eigenprofiles computed over the range of expected energies in the precipitating electron flux, while the horizontal dimension retains a standard orthogonal pixel basis. Simulation results show typical characteristic energy estimation error less than 30% for a 3 km baseline achievable within the confines of the Poker Flat Research Range, using GPS-synchronized Electron Multiplying CCD cameras with broad-band BG3 optical filters that pass prompt auroral emissions.

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Optical tomography of the aurora and EISCAT

Cited by 5 publications

References 14 publications

Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

GPS phase scintillation associated with optical auroral emissions: First statistical results from the geographic South Pole

Reconstruction of Fine-Scale Auroral Dynamics

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