First direct optical observations of plasma flows using afterglow of in discrete aurora

Dahlgren, Hanna; Ivchenko, Nickolay; Lanchester, B. S.; Ashrafi, M.; Whiter, Daniel; Marklund, Göran; Sullivan, J.

doi:10.1016/j.jastp.2008.11.015

Cited by 22 publications

(21 citation statements)

References 32 publications

(41 reference statements)

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“…At the end of the passage the prompt emission moves rapidly to the west, leaving behind an afterglowing O + emission in ASK2. The afterglow of this event has been analysed in Dahlgren et al (2009), who found that the emission decay history was consistent with 1 keV precipitation.…”

Section: Introductionmentioning

confidence: 95%

Energy and flux variations across thin auroral arcs

et al. 2011

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Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz) and spatial (down to tens of metres) resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independently from optical emissions combined with ion-chemistry modelling, and a good agreement is found. A robust method to obtain detailed 2-D maps of the average energy and number flux of small scale aurora is presented. The arcs are stretched in the north-south direction, and the lowest energies are found on the western, leading edges of the arcs. The large ionospheric electric fields (250 mV m<sup>−1</sup>) found from tristatic radar measurements are evidence of strong currents associated with the region close to the optical arcs. The different data sets indicate that the arcs appear on the boundaries between regions with different average energy of diffuse precipitation, caused by pitch-angle scattering. The two thin arcs on these boundaries are found to be related to an increase in number flux (and thus increased energy flux) without an increase in energy

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Section: Introductionmentioning

confidence: 95%

Energy and flux variations across thin auroral arcs

et al. 2011

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“…The theoretical lifetime increases from about 1 s at 200 km altitude to 5 s at above 350 km altitude. The emissions are further described in Dahlgren et al [2008aDahlgren et al [ , 2009.…”

Section: Chemistry Of the Forbidden O + Emission Doublet At 732/733 Nmmentioning

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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“…The molecular oxygen process is sensitive to the higher‐energy electrons, and the atomic oxygen process is sensitive to lower energy electrons. Further details on the emissions measured by ASK can be found in Lanchester et al [] and Dahlgren et al [].…”

Section: Instrumentation and Observationsmentioning

confidence: 99%

Temporal and spatial evolution of auroral electron energy spectra in a region surrounding the magnetic zenith

2014

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We present a new method for estimating the spatial and temporal evolution of the auroral electron energy spectrum at subkilometer and subsecond scales using optical and incoherent scatter radar data. This method is applied to an event on 12 December 2006 when a thin auroral arc that exhibits subkilometer structuring is observed. The energy spectrum and resultant emission rates are estimated for a 10 s period when the arc was in the field of view of the optical instrumentation. Modeled images of the observed aurora are produced using the estimated emission rates and compared with the optical observations of the aurora. We find the modeled images reproduce the structure and dynamics of the observed aurora to within the uncertainties of the models used. The brightness underestimate of about 30% can be explained by the underestimate of the energy flux from the radar measurements.

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First direct optical observations of plasma flows using afterglow of in discrete aurora

Cited by 22 publications

References 32 publications

Energy and flux variations across thin auroral arcs

Energy and flux variations across thin auroral arcs

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

Temporal and spatial evolution of auroral electron energy spectra in a region surrounding the magnetic zenith

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