EISCAT observations of pump‐enhanced plasma temperature and optical emission excitation rate as a function of power flux

Bryers, Carl; Kosch, M. J.; Senior, Andrew; Rietveld, M. T.; Yeoman, T. K.

doi:10.1029/2012ja017897

Cited by 8 publications

(14 citation statements)

References 38 publications

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“…Figure (right) shows the Gaussian heat source profile, Q total for the O‒mode in red and for the X‒mode in black. The heat sources' half widths, w , are both narrow in altitude extent (±5 km of the Gaussian peak) as was found by Bryers et al []. The height, z 0 of the heat source for the O‒mode case is below that of the X‒mode case.…”

Section: Results and Analysissupporting

confidence: 56%

“…For this particular case, the HF reflection altitude was 220 km and the UHR height was 3 km below this. Bryers et al [] showed that for O‒mode polarization, the height of the heat source was found to be close to the UHR height where the majority of the heating occurs. In the case of the X‒mode polarization, the majority of heating is due to the swelling of the pump wave electric field as it approaches reflection.…”

Section: Results and Analysismentioning

confidence: 99%

“…Since the radar analysis assumes a Maxwellian electron flux, J total is the total energy transferred to the Maxwellian electrons by the pump. The method is briefly outlined below but a full description can be found in Bryers et al []. The electron energy equation is described by Schunk and Nagy []:

\overset{2}{sin} I \frac{\partial}{∂z} ((), K^{e} \frac{\partial T_{e}}{∂z}) + \sum Q_{e} + \sum L_{e} = 0

where I is the angle of inclination of the Earth's magnetic field (77.5° for EISCAT).…”

Section: Methodology and Modelingmentioning

confidence: 99%

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A comparison between resonant and nonresonant heating at EISCAT

et al. 2013

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[1] We compare the height-integrated electron heating rates from O-and X-mode HF pump waves to extract the components due to resonant and nonresonant heating mechanisms in the ionosphere. We present results from a November 2011 campaign in Norway, using the European Incoherent Scatter (EISCAT) heater facility and UHF radar. We show that the theoretical nonresonant, ohmic heating due to the electromagnetic pump wave electric field agrees with observations for X-mode pumping. For O-mode pumping, the observed height-integrated heating rate exceeds the theoretical ohmic electron heating rate by a factor of 2-5, the excess being attributed to resonant heating mechanisms. In addition, a persistent UHF ion-line enhancement is observed for O-mode and, more unusually, X-mode pumping. We attribute the latter to O-mode leakage in the X-mode pulse. For O-mode, we see a descent in altitude of the ion-line enhancement and show that this is most likely due to ionization from pump-induced fluxes of suprathermal electrons. We estimate the ionization rate and determine an enhanced electron flux showing that approximately 10-20% of the pump power is transferred to high energy suprathermal electrons.

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Section: Results and Analysissupporting

confidence: 56%

Section: Results and Analysismentioning

confidence: 99%

\overset{2}{sin} I \frac{\partial}{∂z} ((), K^{e} \frac{\partial T_{e}}{∂z}) + \sum Q_{e} + \sum L_{e} = 0

where I is the angle of inclination of the Earth's magnetic field (77.5° for EISCAT).…”

Section: Methodology and Modelingmentioning

confidence: 99%

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A comparison between resonant and nonresonant heating at EISCAT

et al. 2013

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“…The CUTLASS radar backscatter is observed over approximately 6-7 range gates, 15 km each, which is a region in space of the size 90-105 km. Bryers et al [2012] found that the area of the pump wave due to refraction expanded by a factor of 1.2 compared to the free-space area. This would increase the area from 80 km to 96 km which lies within the measured range of 90-105 km.…”

Section: Resultsmentioning

confidence: 99%

“…This is due to low ohmic heating from the pump electromagnetic wave but primarily because weak or no resonances are stimulated to provide additional heating. Bryers et al [2012] showed that for O-mode pumping, the energy from the pump wave is absorbed by the electrons close to the UHR height, and heat conducts up and down the magnetic field. The highest enhanced electron temperatures shown in Figure 1 are localized between 180 and 260 km.…”

Section: Resultsmentioning

confidence: 99%

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

et al. 2013

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[1] We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from 0.5 MW to 100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.Citation: Bryers, C. J., M. J. Kosch, A. Senior, M. T. Rietveld, and T. K. Yeoman (2013), The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT,

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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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EISCAT observations of pump‐enhanced plasma temperature and optical emission excitation rate as a function of power flux

Cited by 8 publications

References 38 publications

A comparison between resonant and nonresonant heating at EISCAT

A comparison between resonant and nonresonant heating at EISCAT

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

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

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