<i>D</i> region absorption effects during high‐power radio wave heating

Tomko, A. A.; Ferraro, Anthony J.; Lee, H. S.

doi:10.1029/rs015i003p00675

Cited by 20 publications

(17 citation statements)

References 6 publications

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“…The HF heating component of the model is described in detail by Cohen et al [2010a] and builds off the work of Tomko et al [1980], Rodriguez [1994], Payne [2007], and Moore [2007]. To summarize, the three‐dimensional model uses a grid, which in this case is defined from 60–95 km in altitude and spans 160 km in each horizontal direction.…”

Section: Theoretical Modelingmentioning

confidence: 99%

The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

et al. 2011

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[1] Experiments for generating extremely low frequency (ELF) radio waves using modulated HF heating of the auroral ionosphere have been conducted and refined at the High Frequency Active Auroral Research Program (HAARP) facility at Gakona, Alaska. Because this technique is dependent on strength of the naturally generated electrojet current system, the amplitude of the generated ELF changes with geophysical conditions. Past work has shown that electrojet current strength as measured by magnetometers often correlates with generated ELF amplitude, but there are periods of poor or negative correlation. We attempt to use additional diagnostics from a radar, riometer, ionosonde, and magnetometer chain to understand how ionospheric conditions affect ELF generation. We then present the results of a statistical model that shows that ELF amplitude is roughly proportional to magnetometer measurements for a fixed value of riometer absorption and that the proportionality constant decreases as riometer absorption increases. Theoretical simulations of modulated heating are conducted for a variety of ionospheric density profiles to verify that denser profiles result in smaller gains for ELF generation as a function of electrojet current at a given electric field.

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Section: Theoretical Modelingmentioning

confidence: 99%

The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

et al. 2011

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“…Getmantsev et al [1974] first showed that ionospheric heaters can generate ELF/VLF waves by periodically heating the ionosphere with high‐frequency (HF) radiation in the megahertz range. This heating modulates electron temperature in the D region ionosphere which leads to modulated conductivity and a time‐varying current at the modulation frequency (see Stubbe and Kopka [1977], Tomko et al [1980], and Ferraro et al [1982] for theoretical descriptions). While this method solves the problem of maintaining large antennas, the strength of the natural currents varies over time.…”

Section: Introductionmentioning

confidence: 99%

Relationship between electrojet current strength and ELF signal intensity in modulated heating experiments

2009

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[1] The High Frequency Active Auroral Research Program (HAARP) facility is used to generate waves in the extremely low frequency (ELF) range via modulated HF heating of the ionosphere. This HF heating modulates the electron temperature in the D region ionosphere and leads to modulated conductivity and a time-varying current which then radiates at the modulation frequency. We investigate the relationship between the intensity of the HAARP-generated ELF signal and the strength of the east-west component of the auroral electrojet as measured by a ground-based magnetometer. We find that under all magnetic conditions, HAARP can generate ELF radiation detectable 37 km away with 73% of tones having an amplitude exceeding 0.15 pT. While strong ELF amplitudes (>1.5 pT) were most common during an enhanced electrojet, a weak electrojet can also support equally high ELF amplitudes. The relative change in ELF amplitude per unit change in electrojet current strength is inversely proportional to the absolute current strength. We interpret the dynamic relationship between ELF amplitude and electrojet current strength in terms of the time-variable ionospheric parameters and HF heating efficiency.Citation: Jin, G., M. Spasojevic, and U. S. Inan (2009), Relationship between electrojet current strength and ELF signal intensity in modulated heating experiments,

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“…In this paper, the absorption of wave energy approximately follows the 2‐D Gaussian distribution. Therefore, the energy flux of the incident wave can be expressed as [ Tomko et al ., ].

I ((),, r, h) = \frac{normalE normalR normalP}{4 π h^{2}} normalexp ((), prefix- 2 true {true\int}_{h_{0}}^{h} \frac{ω}{c} normalI normalm ((), n) normald h) normalexp ((), prefix- {(r - r_{0})}^{2} true/ σ_{x}^{2})

where ERP is the effective radiated power of the radio wave, h 0 is the lower boundary of the ionosphere, r 0 = 0 is the center of the heating beam, and σ x is the radiate scale which can be expressed as

σ_{x} = h_{r} normaltan \frac{φ}{2} true/ \sqrt{normalln 2}

where h r is the reflection height and ϕ is the half‐power width of the heating beam [ Kraus and Marhefka , ].…”

Section: Theoretical Modelmentioning

confidence: 99%

Saturation effects of the lower ionosphere based on two‐dimensional HF heating model

Cheng

Guo

2017

JGR Space Physics

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This paper presents a two‐dimensional (2‐D) theoretical model of the lower ionospheric heating by high‐frequency (HF) electromagnetic waves. Compared with the traditional one‐dimensional model, we develop the half‐power width of the heating beam into the theoretical formulations, which dictates the 2‐D distribution characteristics of electron temperature and density perturbations; we also introduce the Sodankylä Ion Chemistry (SIC) model. Based on this numerical model, the saturation effect of ionospheric electron temperature and density is investigated, and simulation is performed by heating at a wave frequency of 6 MHz. Results show that because of energy absorption, the electron temperature peaks at 74 km, and the relative increment of electron density peaks at 94 km in the height direction. Conversely, both the maximum perturbations of electron temperature and density appear on the beam center in the horizontal direction. Second, the saturation time of electron temperature initially increases slowly and then rapidly with increased height. Meanwhile, the saturation time of electron density decreases with increased height. In the horizontal aspect, both the saturation time of electron temperature and density are symmetrical at approximately the position of the beam center owing to the initial Gaussian distribution. Electron temperature far from the beam center results in a long saturation time. Conversely, with increased distance from the beam center, the saturation time of electron density decreases.

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D region absorption effects during high‐power radio wave heating

Cited by 20 publications

References 6 publications

The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

Relationship between electrojet current strength and ELF signal intensity in modulated heating experiments

Saturation effects of the lower ionosphere based on two‐dimensional HF heating model

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