High‐latitude HF‐induced airglow displaced equatorwards of the pump beam

Kosch, M. J.; Rietveld, M. T.; Hagfors, T.; Leyser, T. B.

doi:10.1029/2000gl003754

Cited by 69 publications

(78 citation statements)

References 28 publications

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“…Whilst the pump frequency does not appear important, pump power determines the electron temperature enhancement and plasma depletion depth in their model. However, we note that with a pump frequency of 2.85 MHz HAARP produces an O1D optical emission of 100 -300 R for 11 MW ERP Kosch et al, 2005], whereas for pump frequencies >4 MHz EISCAT produces O1D optical intensities of order 100 R for pump powers of 70-200 MW ERP [Kosch et al, 2000[Kosch et al, , 2002bRietveld et al, 2003]. Since the O1D 630 nm pumpinduced optical emission is at least partly a function of electron temperature [e.g., Ashrafi et al, 2006;Gustavsson et al, 2002], we conclude that low pump powers at HAARP are compensated by pumping the ionosphere near the second electron gyroharmonic, which seems to produce significant electron temperature enhancements.…”

Section: Resultsmentioning

confidence: 99%

“…Almost immediately, it was noticed that the optical emission was significantly more intense in the magnetic zenith. For vertical pumping at EISCAT [Kosch et al, 2000] and HAARP [Pedersen and Carlson, 2001] the emission region was displaced toward the magnetic zenith $13°and $15°away, respectively. The brightest optical emission was sometimes outside the À3 dB locus of the pump beam.…”

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

et al. 2007

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[1] On 4 February 2005 the High-Frequency Active Auroral Research Program (HAARP) facility was operated at 2.85 MHz to produce artificial optical emissions in the ionosphere while passing through the second electron gyroharmonic. All-sky optical recordings were performed with 15 s integration, alternating between 557.7 and 630 nm. We report the first optical observations showing the temporal evolution of large-scale pump wave selffocusing in the magnetic zenith, observed in the 557.7 nm images. These clearly show that the maximum intensity was not reached after 15 s of pumping, which is unexpected since the emission delay time is <1 s, and that the optical signature had intensified in a much smaller region within the beam after 45 s of pumping. In addition, adjacent regions within the beam lost intensity. Radar measurements indicate a plasma depletion of $1% near the HF reflection altitude. Ray tracing of the pump wave through the plasma depletion region, which forms a concave reflecting radio wave mirror, reproduces the optical spatial morphology. A radio wave flux density gain of up to $30 dB may occur. In addition, the ray trace is consistent with the observed artificial optical emissions for critical plasma frequencies down to $0.5 MHz below the pump frequency.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

et al. 2007

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“…Artificial electron heating by high power transmitters in the 3-7 MHz range (Rietveld et al, 1993) has been shown to have an effect on atmospheric phenomena, such as auroral emission and airglow (Jones et al, 1986;Kosch et al, 2000), and on the radar phenomenon Polar Mesospheric Summer Echoes (PMSE) (Chilson et al, 2000;Belova et al, 2003). The transmitted heating wave accelerates and heats electrons while the neutrals and ions are unaffected.…”

Section: Introductionmentioning

confidence: 99%

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

2005

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Abstract.We have considered the effect that a local reduction in the electron density (an electron bite-out), caused by electron absorption on to dust particles, can have on the artificial electron heating in the height region between 80 to 90 km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without biteouts, the heated electron temperature T e,hot will generally decrease smoothly with height in the PMSE region or there may be no significant heating effect present. Within a biteout T e,hot will decrease less rapidly and can even increase slightly with height if the bite-out is strong. We have looked at recent observations of PMSE which are affected by artificial electron heating, with a heater cycling producing the new overshoot effect. According to the theory for the PMSE overshoot the fractional increase in electron temperature T e,hot /T i , where T i is the unaffected ion temperature = neutral temperature, can be found from the reduction in PMSE intensity as the heater is switched on. We have looked at results from four days of observations with the EIS-CAT VHF radar (224 MHz), together with the EISCAT heating facility. We find support for the PMSE overshoot and heating model from a sequence of observations during one of the days where the heater transmitter power is varied from cycle to cycle and where the calculated T e,hot /T i is found to vary in proportion to the transmitter power. We also looked for signatures of electron bite-outs by examining the variation of T e,hot /T i with height for the three other days. We find that the height variation of T e,hot /T i is very different on the three days. On one of the days we see typically that this ratio can increase with height, showing the presence of a bite-out, while on the next day the heating factor mainly decreases with height, indicating that the fractional amount of dust is low, so that the electron density is hardly affected by it. On the third day there is little heating effect on the PMSE layer. This is probably due to a sufficiently high electron densityCorrespondence to: O. Havnes (oha003@asp.uit.no) in the atmosphere below the PMSE layer, so that the transmitted heater power is absorbed in these lower layers. On this day the D-region, as given by the UHF (933 MHz) observations, extends deeper down in the atmosphere than on the other two days, indicating that the degree of ionization in and below the PMSE layers is higher as well.

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“…In reality, from the CUTLASS HF radar measurements the spatial size of the heated patch can occupy a region significantly larger than the area contained within 3 dB contour . It is interesting to note that a southward displacement preference was observed in other heater-induced phenomena during other HF pumping experiments, such as the radio-induced airglow (Kosch et al, 2000), and Langmuir turbulence (Isham et al, 1999) which may excite energetic electrons. The behavior of the AE index describing the auroral activity as a whole also shows that the substorm occurred at 19:30 UT.…”

Section: Observational Results Of 2 October 1998mentioning

confidence: 99%

“…Considerable success has been achieved by the use of the EISCAT HF Heating facility located at auroral latitudes in Tromsø, Norway (see, for example, Stubbe, 1996 (and references therein); Thidé et al, 1982;Rietveld et al, 1993Rietveld et al, , 2000Robinson et al, 1998;Leyser, 2001;Leyser et al, 1989;Isham et al, 1990;1999;Jones et al, 1984;Honary et al, 1999;Yeoman et al, 1997;Brändström et al, 1999;Eglitis et al, 1998;Blagoveshchenskaya et al, 1998b;Kosch et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere

Blagoveshchenskaya

Борисова²,

Kornienko³

et al. 2005

Ann. Geophys.

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Abstract. Experimental results from three ionospheric HF pumping experiments in overdense E or F regions are summarized. The experiments were conducted by the use of the EISCAT HF Heating facility located near Tromsø, Norway, allowing HF pumping the ionosphere in a near geomagnetic field-aligned direction. Distinctive features related to auroral activations in the course of the experiments are identified. Typical features observed in all experiments are the following: generation of scattered components in dynamic HF radio scatter Doppler spectra; strong increase of ion temperatures T i and local ionospheric electric field E 0 ; modification of the auroral arc and local spiral-like formation. However, some effects were observed only when the HF pump wave was reflected from the F 2 layer. Among them are the generation of intense field-aligned ion outflows, and a strong increase in the electron temperature T e with altitude. A possible scenario for the substorm triggering due to HF pumping into an auroral ionosphere is discussed. The authors present their interpretation of the data as follows. It is suggested that two populations of charged particles are at play. One of them is the runaway population of electrons and ions from the ionosphere caused by the effects of the powerful HF radio wave. The other is the population of electrons that precipitate from the magnetosphere. It is shown that the hydrodynamical equilibrium was disrupted due to the effects of the HF pumping. We estimate that the parallel electric field can reach values of the order of 30 mV/m during substorm triggering.

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High‐latitude HF‐induced airglow displaced equatorwards of the pump beam

Cited by 69 publications

References 28 publications

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere

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