Simultaneous imaging of aurora on small scale in OI (777.4 nm) and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;1P to estimate energy and flux of precipitation

Lanchester, B. S.; Ashrafi, M.; Ivchenko, Nickolay

doi:10.5194/angeo-27-2881-2009

Cited by 35 publications

(66 citation statements)

References 20 publications

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“…Using high‐resolution optical instruments and incoherent scatter radar, Lanchester et al [] noted a very large energy flux (>500 mW/m 2 ) within a 100 m wide filament of monoenergetic precipitation, located within a wider region of precipitation of lower energy flux. Other observations of auroral filaments and curls have shown that they are associated with both higher energy and higher electron fluxes than the surrounding precipitation [ Lanchester et al , ; Dahlgren et al , , ]. Ivchenko et al [] showed that curls are caused by high‐energy precipitation, which would be a signature of an electrostatic acceleration mechanism above the ionosphere, whereas auroral rays are the result of both high‐ and low‐energy electrons, which indicates acceleration by wave‐particle interactions.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…The imagers operate at 32 frames per second. Here, we present data obtained with the 6730 Å filter for the N21P band emission excited by high-energy electron precipitation (ASK1, e.g., Ashrafi et al, 2009) and the 7774 Å filter observing emission from atomic oxygen excited by low-energy electron precipitation (ASK3, e.g., Lanchester et al, 2009). The field of view of these imagers is 6.2 × 6.2 • and is centered at magnetic zenith.…”

Section: Instrumentation and Experimentsmentioning

confidence: 99%

“…The Auroral Structures and Kinetics (ASK, e.g., Lanchester et al, 2009) optical instrument is co-located with the EISCAT Svalbard radar facility. ASK operates three imagers observing in the direction of the geomagnetic field.…”

Section: Instrumentation and Experimentsmentioning

confidence: 99%

Auroral ion acoustic wave enhancement observed with a radar interferometer system

et al. 2015

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Abstract. Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EIS-CAT) radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the radar site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements, we show that the enhanced backscattering region is of limited extent in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size; however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900 × 500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar look direction, our observations are consistent with the NEIAL echo occurring on field lines with particle precipitation.

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“…At this wavelength there are also underlying N 2 emission bands, produced by high-energy precipitation [Dahlgren et al, 2008a]. The third imager measures the atomic oxygen emission at 777.4 nm (I O ), which in the aurora is most sensitive to low-energy precipitation [Lanchester et al, 2009] and results from direct excitation of atomic oxygen in the ionospheric F region. It is also produced by high-energy precipitating electrons through dissociative excitation of molecular oxygen in the E region.…”

Section: Instrumentationmentioning

confidence: 99%

Coexisting structures from high‐ and low‐energy precipitation in fine‐scale aurora

Dahlgren

Lanchester

Ivchenko

2015

Geophysical Research Letters

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High‐resolution multimonochromatic measurements of auroral emissions have revealed the first optical evidence of coexisting small‐scale auroral features resulting from separate high‐ and low‐energy populations of precipitating electrons on the same field line. The features exhibit completely separate motion and morphology. From emission ratios and ion chemistry modeling, the average energy and energy flux of the precipitation is estimated. The high‐energy precipitation is found to form large pulsating patches of 0.1 Hz with a 3 Hz modulation, and nonpulsating coexisting discrete auroral filaments. The low‐energy precipitation is observed simultaneously on the same field line as discrete filaments with no pulsation. The simultaneous structures do not interact, and they drift with different speeds in different directions. We suggest that the high‐ and low‐energy electron populations are accelerated by separate mechanisms, at different distances from Earth. The small‐scale structures could be caused by local instabilities above the ionosphere.

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Simultaneous imaging of aurora on small scale in OI (777.4 nm) and N<sub>2</sub>1P to estimate energy and flux of precipitation

Cited by 35 publications

References 20 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

Auroral ion acoustic wave enhancement observed with a radar interferometer system

Coexisting structures from high‐ and low‐energy precipitation in fine‐scale aurora

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