Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere

Eliasson, Bengt; Papadopoulos, K.

doi:10.1029/2009ja014213

Cited by 8 publications

(10 citation statements)

References 11 publications

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“…The resulting Cowling conductivity

σ_{C} = (σ_{H}^{2} / σ_{P}^{2} + 1) σ_{P}

, is a few orders of magnitude larger than the Pedersen conductivity in the E region. For the case when magnetic fields are injected into the ionosphere by a ground‐based antenna from below [ Eliasson and Papadopoulos , 2009], it was found that the Cowling effect can lead to intense horizontal currents and vertical electric fields in the E‐region. For the case considered here, we see inFigure 8h that a sharp drop of the amplitude of B x at z ≈ 100 km is associated with the intense current component j y via Ampère's law

\partial B_{x} / \partial z = μ_{0} j_{y}

, and a large vertical electric field E z in Figure 8g.…”

Section: Dynamics Of Elf Waves Generated In the F2 Regionmentioning

confidence: 99%

“…Low‐frequency waves in the ionosphere, can be excited by lightning discharges [ Greifinger and Greifinger , 1976; Uman , 1987; Berthelier et al , 2008; Milikh et al , 1995], seismic events [ Hayakawa et al , 2006], and ionospheric heating by powerful high‐frequency (HF) transmitters [ Rietveld et al , 1984, 1987, 1989; Barr , 1998; Papadopoulos et al , 1990, 2005]. The injection of ELF electromagnetic waves into the equatorial E‐region by ground‐based antennas was suggested by Eliasson and Papadopoulos [2009], who found that induced strong horizontal currents and related vertical electric fields can be formed in a few kilometers thick layer, close to the plasma‐free space boundary. This effect is reminiscent of the equatorial electrojet [ Forbes and Lindzen , 1976; Forbes , 1981; Rishbeth , 1997; Rastogi , 1989] where a potential drop due to tidal motion along the equatorial line gives rise to an intense electron current by the Cowling effect.…”

Section: Introductionmentioning

confidence: 99%

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Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

Eliasson¹,

Chang²,

Papadopoulos³

2012

J. Geophys. Res.

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[1] We present a theoretical and numerical study of the generation of extremely low frequency (ELF) and ultra-low frequency (ULF) waves by the modulation of the electron pressure at the F2-region with an intense high-frequency electromagnetic wave. The study is based on a cold plasma Hall-MHD model, including electron-neutral and ion-neutral collisions, which governs the dynamics of magnetostatic waves and their propagation through the ionospheric layers. Magnetosonic waves generated in the F2 region are propagating isotropically and are channeled in the ionospheric waveguide, while shear Alfvén waves are propagating along the magnetic field. To penetrate the ionosphere from the F2 peak at 300 km to the ground, the magnetostatic waves first propagate as magnetosonic or shear Alfvén waves that encounter a diffusive layer from about 150 km to 120 km where the Pedersen conductivity dominates, and then as helicon (whistler-like) mode waves from about 120 km to 80 km where the ions are collisionally glued to the neutrals and the Hall conductivity dominates. By performing numerical simulations and studying the dispersive properties of the wave modes, we investigate the dynamics and penetration of ELF/ULF waves through the ionospheric layers to the ground and along the geomagnetic field lines to the magnetosphere. Realistic profiles of the ionospheric profiles of conductivity and density are used, together with different configurations of the geomagnetic field, relevant for both the high, mid and equatorial latitudes. Some of the results are compared with recent HAARP experiments.Citation: Eliasson, B., C.-L. Chang, and K. Papadopoulos (2012), Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region,

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“…The resulting Cowling conductivity

σ_{C} = (σ_{H}^{2} / σ_{P}^{2} + 1) σ_{P}

\partial B_{x} / \partial z = μ_{0} j_{y}

, and a large vertical electric field E z in Figure 8g.…”

Section: Dynamics Of Elf Waves Generated In the F2 Regionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

Eliasson¹,

Chang²,

Papadopoulos³

2012

J. Geophys. Res.

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“…Similar to the previous work [15], we assume a very simple model for the antenna, that of an equivalent infinite length wire in the y direction located at x = z = 0, so that,…”

Section: Interaction Model and Simulation Setupmentioning

confidence: 99%

“…However, the interaction of ELF range electromagnetic fields with E-region is relatively less understood. Eliasson and Papadopoulos [15] studied generation and penetration of the ELF current and electromagnetic fields into the equatorial E-region. They found that the interaction of the ELF pulsed and continuous wave fields with the equatorial E-region leads to the generation of both vertical and horizontal currents which penetrate into ionospheric layers as Helicon waves.…”

Section: Introductionmentioning

confidence: 99%

Penetration of ELF Currents and Electromagnetic Fields into the Off-Equatorial E-Region of the Earth's Ionosphere

Jain,

Eliasson,

Sharma

et al. 2012

Preprint

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The generation of ELF (of the order of 10 Hz) currents and electromagnetic fields in the off-equatorial E-region (90-120 km) of the Earth's ionosphere and their subsequent penetration into the deeper ionospheric layers is studied theoretically and numerically. These ELF currents and fields are generated by the interaction of an electromagnetic pulse with the E-region at its lower boundary located at 90 km above the Earth's surface. The wave penetration (with a typical wavelength of the order of 10 km) of the generated ELF currents and fields into the deeper ionospheric layers up to 120 km takes place due to the dominance of the Hall conductivity over the Pederson conductivity in the region between 90-120 km and penetration becomes diffusive above 120 km. During night time, the increase in the wave speed due to the reduced conductivities leads to the deeper penetration. As the angle between Earth's magnetic field and horizontal is increased (going away from the equator), the currents and fields penetrate deeper into the ionospheric layers with increased wavelength, the magnitudes of horizontal (east-west) and vertical currents decrease near the boundary and the vertical electric field decreases drastically. The horizontal (east-west) current integrated along vertical is fitted with a current distribution which can be replaced by a line current raised above its actual height by the half width of the current distribution for the purpose of the calculation of its radiation. The maximum of the total east-west current (310 Amps) remains same for various simulation parameters due to the magnetic shielding.

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“…Also, the electromagnetic perturbation in the neutral atmosphere is estimated by analytic expression, and the inversely spatial Fourier transform is applied to obtain the real space wave field (Eliasson and Papadopoulos, 2009;Eliasson et al, 2012).…”

Section: Xu Et Al: Numerical Study Of the Generation And Propagatmentioning

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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Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere

Cited by 8 publications

References 11 publications

Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

Generation of ELF and ULF electromagnetic waves by modulated heating of the ionospheric F2 region

Penetration of ELF Currents and Electromagnetic Fields into the Off-Equatorial E-Region of the Earth's Ionosphere

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

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