First estimates of volume distribution of HF-pump enhanced emissions at 6300 and 5577 Å: a comparison between observations and theory

Gustavsson, B.; Kosch, M. J.; Wong, A. Y.; Pedersen, T. R.; Heinselman, C. J.; Mutiso, C. K.; Bristow, B.; Hughes, John M.; Wang, Weiyuan

doi:10.5194/angeo-26-3999-2008

Cited by 10 publications

(9 citation statements)

References 30 publications

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“…Modelling of the electron temperature enhancements in the interaction region accounts for only one-third of the total O ( 1 D) emission intensity. This points towards a modification of the Maxwellian electron energy spectrum whereby strong acceleration causes a higher flux of suprathermal electrons (Gustavsson et al 2008). Observations of N 2 + (1 NG, blue-line, 427.8 nm) (Holma et al 2006), with an excitation threshold of 18.6 eV, confirm this.…”

Section: Introductionmentioning

confidence: 65%

Aspect angle sensitivity of pump-induced optical emissions at EISCAT

et al. 2014

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We investigate the aspect angle sensitivity of the pump-induced artificial optical emissions in the ionosphere over the European Incoherent Scatter Scientific Association (EISCAT) high-frequency transmitter facility at Ramfjord, Norway, as a function of the pump beam launch angle relative to the magnetic field line direction. The highest intensity optical emissions occur when the pump beam pointing direction is in the magnetic zenith (approximately 12°S of local zenith). For pump beam directions further north from field aligned, the optical emission intensity decreases for the same pump power. In addition, the primary photon-emitting region becomes displaced towards the magnetic zenith relative to the pump beam and for larger aspect angles, the brightest emissions were found to be outside the −3-dB pump beam width. The Cooperative UK Twin-Located Auroral Sounding System (CUTLASS) coherent scatter high-frequency (HF) radar detected a quasi-constant level of backscatter power from the pumped ionosphere, indicating that saturated striations were formed for all pump beam directions. This indicates that the presence of upper-hybrid resonance is not sufficient to explain the angular sensitivity of the optical emissions.

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Section: Introductionmentioning

confidence: 65%

Aspect angle sensitivity of pump-induced optical emissions at EISCAT

et al. 2014

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“…This causes electron heating of the bulk thermalized plasma up to 4000 K (see Figure ), as observed by the EISCAT radar, as well as accelerating a small but significant flux of suprathermal electrons to energies up to at least 11 eV, as observed by the artificially induced optical emissions (see Figure ). Previous side‐viewing observations of pump‐induced optical emissions show they appear up to 100–200 km in height extent [ Gustavsson et al ., ; Pedersen et al ., ], showing that the suprathermal electrons propagate upward from the plasma resonance region and therefore constitute a downward current in the topside ionosphere. How rapidly the pump‐induced suprathermal electrons propagate up the magnetic field line has never been observed experimentally because the low cadence of the imagers.…”

Section: Discussionmentioning

confidence: 99%

“…For a different experiment, Gustavsson et al . [] estimated that the full width at half maximum (FWHM) optical intensity was ~ ±24.5 km, assuming a Gaussian distribution, around a peak altitude of 204 km, accounting for 80.3% of the photon production volume. No side‐viewing optical data were available on 23 October 2013 due to clouds, but such data from 22 October 2013 are consistent with the optical FWHM estimate albeit at a higher altitude of ~225 km (Figure of N. Blagoveshchenskaya, submitted manuscript, 2014).…”

Section: Discussionmentioning

confidence: 99%

First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT

Kosch

Vickers

Ogawa

et al. 2014

Geophysical Research Letters

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We have developed an active ground-based technique to estimate the steady state field-aligned anomalous electric field (E*) in the topside ionosphere, up to~600 km, using the European Incoherent Scatter (EISCAT) ionospheric modification facility and UHF incoherent scatter radar. When pumping the ionosphere with high-power high-frequency radio waves, the F region electron temperature is significantly raised, increasing the plasma pressure gradient in the topside ionosphere, resulting in ion upflow along the magnetic field line. We estimate E* using a modified ion momentum equation and the Mass Spectrometer Incoherent Scatter model. From an experiment on 23 October 2013, E* points downward with an average amplitude of 1.6 μV/m, becoming weaker at higher altitudes. The mechanism for anomalous resistivity is thought to be low-frequency ion acoustic waves generated by the pump-induced flux of suprathermal electrons. These high-energy electrons are produced near the pump wave reflection altitude by plasma resonance and also result in observed artificially induced optical emissions.

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“…To obtain accurate projections, both the field of view and the sensitivity of the cameras need to be known to high accuracy. Line‐of‐sight calibration was achieved by identifying stars in the image with the corresponding stars in the Yale Bright Star Catalog (Hoffleit & Jaschek, ), the applied calibration method is described further in Gustavsson et al (). Absolute intensity calibration factors from Wang () were used to convert the Charge‐Coupled Device counts to Rayleighs for images in 5,577 and in 6,300 Å.…”

Section: Aurora Modelingmentioning

confidence: 99%

“…Gustavsson et al () achieved 3‐D emission rate reconstruction by using tomography‐like inversion methods. The same method was later employed by Gustavsson et al () to estimate the volume emission rates in both I 6300 and in I 5577 using the High‐Frequency Active Auroral Research Program facility and two imaging stations. Shindin et al () estimated the 3‐D emission rates of I 6300 at midlatitudes, induced by the Sura heating facility, using two imaging stations.…”

Section: Introductionmentioning

confidence: 99%

The 3‐D Distribution of Artificial Aurora Induced by HF Radio Waves in the Ionosphere

et al. 2019

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We present 3-D excitation rate estimates of artificial aurora in the ionospheric F layer, induced by high-frequency radio waves from the European Incoherent Scatter heating facility. Simultaneous imaging of the artificial aurora was done with four separate Auroral Large Imaging System stations, permitting tomography-like 3-D auroral reconstruction of the enhanced atomic oxygen emissions at 6,300, 5,577, and 8,446 Å. Inspection of the 3-D reconstructions suggests that the distribution of energized electrons is less extended in altitude than predicted by transport calculations of electrons accelerated to 2-100 eV. A possible reason for this discrepancy is that high-frequency pumping might induce an anisotropic distribution of energized electrons.Plain Language Summary Auroral lights can be artificially generated by transmitting high-frequency radio waves with high power into the upper atmosphere. In this article, we use multiple viewpoint imaging of artificially produced aurora to estimate the 3-D distribution of the auroral lights by employing tomography-like techniques. The 3-D distribution is estimated in the red, green, and infrared auroral emission lines with wavelengths of 630.0, 557.7, and 844.6 nm, respectively. These emissions are excited by energetic electrons, which have been accelerated through interaction processes between the transmitted radio waves and plasma in the upper atmosphere, at an altitude of about 220-250 km. We observe that the estimated 3-D auroral distributions are less extended in altitude than indicated by previous theoretical work. A possible reason for this disagreement is that the radio wave-plasma interaction processes might lead to a direction dependent electron acceleration.

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First estimates of volume distribution of HF-pump enhanced emissions at 6300 and 5577 Å: a comparison between observations and theory

Cited by 10 publications

References 30 publications

Aspect angle sensitivity of pump-induced optical emissions at EISCAT

Aspect angle sensitivity of pump-induced optical emissions at EISCAT

First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT

The 3‐D Distribution of Artificial Aurora Induced by HF Radio Waves in the Ionosphere

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