ELF/VLF wave generation from the beating of two HF ionospheric heating sources

Cohen, M. B.; Moore, R. C.; Gołkowski, M.; Lehtinen, N. G.

doi:10.1029/2012ja018140

Cited by 31 publications

(28 citation statements)

References 44 publications

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“…Because there is no high harmonics in signals of beat-wave modulation. With the HAARP's heating facility, Cohen et al [23] verified this conclusion.…”

Section: Numerical Results Analysis and Discussionsupporting

confidence: 63%

Numerical Simulations of Elf/VLF Wave Generated by Modulated Beat-Wave Ionospheric Heating in High Latitude Regions

Li¹,

Zhan²,

Wu³

et al. 2016

PIER M

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Abstract-Based on the theory of ionospheric heating, with the self-consistent model in the low ionosphere, the Extremely-Low-Frequency (ELF) and Very-Low-Frequency (VLF) waves generated by modulated beat-wave ionospheric heating are analyzed theoretically. In the consideration of the stratified ionosphere, the magnetic fields generated by the equivalent ELF/VLF dipole source above the sea surface are studied by using the quasi-longitudinal approximation method. Taking the high latitude regions as an example, the variations of the electron temperature, the increments of Pedersen and Hall conductivities and the changing of the oscillating current density with the modulation frequency in beatwave heating are numerically discussed. The distribution of the magnetic fields is presented. It turns out that in high latitude regions, the efficiency of rectangular wave modulated heating in generating ELF/VLF wave is higher than that of modulated beat-wave heating, and the order of magnitude of the magnetic fields received above the sea surface is 10 −7 A/m in beat-wave modulation.

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“…Because there is no high harmonics in signals of beat-wave modulation. With the HAARP's heating facility, Cohen et al [23] verified this conclusion.…”

Section: Numerical Results Analysis and Discussionsupporting

confidence: 63%

Numerical Simulations of Elf/VLF Wave Generated by Modulated Beat-Wave Ionospheric Heating in High Latitude Regions

Li¹,

Zhan²,

Wu³

et al. 2016

PIER M

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“…This effect most likely results from the HF interference pattern produced by the physical separation of the north and south HAARP subarrays. Similar effects have been observed during ''beat-wave'' ELF and VLF wave generation experiments: the lateral separation of the phase centers of the two transmitting subarrays produces a HF phasing pattern at ionospheric altitudes that in turn results in a highly directional ELF and VLF radiation pattern [21,22]. This phasing effect can be large, producing AE20 dB amplitude variations as a function of azimuth depending on the ELF and VLF wave frequency and the distance to the receiver [21,22].…”

supporting

confidence: 59%

“…Comparison with theory.-The dual-beam ionospheric HF heating model presented in this work is based on past work [9,22,23], but accounts for electron density changes as a function of HF heating [24]. The model accounts for the HF phasing effect that results from the physical separation of the HF sources [21,22].…”

mentioning

confidence: 99%

“…The model accounts for the HF phasing effect that results from the physical separation of the HF sources [21,22]. Using this model, we aim to produce order-of-magnitude amplitude comparisons with experimental observations, to identify the theoretical altitude of the ELF and VLF source region, and to determine the dominant component of the thermal cubic nonlinearity mechanism that produces the ELF and VLF source.…”

mentioning

confidence: 99%

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Observations of Ionospheric ELF and VLF Wave Generation by Excitation of the Thermal Cubic Nonlinearity

et al. 2013

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Extremely-low-frequency (ELF, 3-3000 Hz) and very-low-frequency (VLF, 3-30 kHz) waves generated by the excitation of the thermal cubic nonlinearity are observed for the first time at the High-Frequency Active Auroral Research Program high-frequency transmitter in Gakona, Alaska. The observed ELF and VLF field amplitudes are the strongest generated by any high frequency (HF, 3-30 MHz) heating facility using this mechanism to date. This manner of ELF and VLF generation is independent of naturally forming currents, such as the auroral electrojet current system. Time-of-arrival analysis applied to experimental observations shows that the thermal cubic ELF and VLF source region is located within the collisional D-region ionosphere. Observations are compared with the predictions of a theoretical HF heating model using perturbation theory. For the experiments performed, two X-mode HF waves were transmitted at frequencies ω1 and ω2, with |ω2-2ω1| being in the ELF and VLF frequency range. In contrast with previous work, we determine that the ELF and VLF source is dominantly produced by the interaction between collision frequency oscillations at frequency ω2-ω1 and the polarization current density associated with the lower frequency HF wave at frequency ω1. This specific interaction has been neglected in past cubic thermal nonlinearity work, and it plays a major role in the generation of ELF and VLF waves.

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“…This hypothesis was first suggested by Willis and Davis (1973) and was then proved when artificially excited low-frequency signals were detected in an experiment for the first time (Getmantsev et al, 1974). A series of experiments of generating low-frequency waves following this mechanism were carried out at the European Incoherent Scatter Scientific Association (EISCAT) and the High Frequency Active Auroral Research Program (HAARP; Cohen et al, 2012;Agrawal and Moore, 2012;Ferraro et al, 1984;Papadopoulos et al, 2003), and this mechanism was named PEJ (polar electrojet) (Stubbe and Kopka, 1977;Barr et al, 1991). The method of artificially generating low-frequency waves by modulating the lower ionosphere is completely dependent on the existence of quasi-stationary ionospheric currents, which to some extent limits the location of the heating facility to the high and equatorial latitudes and also makes the generation of ULF waves more unpredictable (Papadopoulos et al, 2011b).…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes

Xu¹,

Zhou²,

Shi³

et al. 2016

Ann. Geophys.

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Abstract. Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) Jicamarca (11.95 • S, 76.87 • W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.

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ELF/VLF wave generation from the beating of two HF ionospheric heating sources

Cited by 31 publications

References 44 publications

Numerical Simulations of Elf/VLF Wave Generated by Modulated Beat-Wave Ionospheric Heating in High Latitude Regions

Numerical Simulations of Elf/VLF Wave Generated by Modulated Beat-Wave Ionospheric Heating in High Latitude Regions

Observations of Ionospheric ELF and VLF Wave Generation by Excitation of the Thermal Cubic Nonlinearity

Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes

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