A FDTD scheme for the computation of VLF-LF propagation in the anisotropic earth-ionosphere waveguide

Thévenot, Marc; Bérenger, Jean-Pierre; Monédière, Thierry; Jecko, F.

doi:10.1007/bf02995540

Cited by 51 publications

(33 citation statements)

References 8 publications

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“…Luckily, the whole FDTD domain is symmetric around the z axis, which allows us to reduce our problem to a two-dimensional (2-D) one by means of symmetry, which vastly reduces the computation and storage required for the simulation. As shown in Figure 1, the geometry of the full-wave FDTD model is based on 2-D spherical coordinates with the sector region defined by the center of the Earth (Bérenger, 2002;Thèvenot et al, 1999).…”

Section: Theory and Methodsmentioning

confidence: 99%

On the Accuracy of Ray‐Theory Methods to Determine the Altitudes of Intracloud Electric Discharges and Ionospheric Reflections: Application to Narrow Bipolar Events

Liu

Pérez‐Invernón

et al. 2020

JGR Atmospheres

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Narrow bipolar events (NBEs) (also called narrow bipolar pulses [NBPs] or compact intracloud discharges [CIDs]) are energetic intracloud discharges characterized by narrow bipolar electromagnetic waveforms identified from ground-based very low frequency (VLF)/low-frequency (LF) observations. The simplified ray-theory method proposed by Smith et al. (1999, https://doi.org/10.10292004, https://doi.org/10.1029/2002RS002790) is widely used to infer the altitude of intracloud lightning and the effective (or virtual) reflection height of the ionosphere from VLF/LF signals. However, due to the large amount of high-frequency components in NBEs, the propagation effect of the electromagnetic fields for NBEs at large distance depends nontrivially on the geometry and the effective conductivity of the Earth-ionosphere waveguide (EIWG). In this study, we investigate the propagation of NBEs by using a full-wave Finite-Difference Time-Domain (FDTD) approach. The simulated results are compared with ground-based measurements at different distances in Southern China, and we assess the accuracy of the simplified ray-theory method in estimating the altitude of the NBE source and the effective reflection height of the ionosphere. It is noted that the evaluated NBE altitudes have a slight difference of about ±1 km when compared with the full-wave FDTD results, while the evaluated ionospheric reflection heights are found to be bigger than those obtained from FDTD model by about 5 km. Key Points:• The propagation effect of NBEs is analyzed using full-wave model and compared with measurement • The simplified ray-theory method might require correction comparing to the full-wave model • We quantify errors in the ionospheric height evaluated from the Smith method

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Section: Theory and Methodsmentioning

confidence: 99%

On the Accuracy of Ray‐Theory Methods to Determine the Altitudes of Intracloud Electric Discharges and Ionospheric Reflections: Application to Narrow Bipolar Events

Liu

Pérez‐Invernón

et al. 2020

JGR Atmospheres

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“…Figure 2 shows the process of the 2-D S-FDTD iteration. Equations ( 12), (15), and ( 18) are new equations for the standard deviation of the magnetic and electric fields respectively. Equations ( 22), (23), and (24) are Mur absorbing boundary condition on the S-FDTD method.…”

Section: Variance Of Fieldsmentioning

confidence: 99%

“…The FDTD method has been a classical EM calculation approach to solve EM problems in the time domain, including EM pulse propagation [13], Earth-ionosphere wave propagation [14][15][16] etc. Stochastic FDTD (S-FDTD) is an algorithm founded on traditional FDTD, which can calculate the variance and mean of the field efficiently.…”

Section: Introductionmentioning

confidence: 99%

Stochastic FDTD for stochastic problems with axial symmetry

Wang

Mao

et al. 2022

IET Microwaves Antenna & Prop

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The random parameters remain hard to tackle for a long time in electromagnetic (EM) computations. Aiming at the time‐dependent uncertainty in the axially symmetric structures, the formulations of the stochastic finite‐difference time‐domain (S‐FDTD) method are derived, and the effectiveness is verified by a cylindrical ring structure. The simulation results indicate that the efficiency of S‐FDTD method is much higher than that of the polynomial chaos (PC) method and the Monte Carlo (MC) method, that is, the S‐FDTD method only takes about 3% of the computation time of the PC method and 0.03% of the computation time of the MC method with slightly lower accuracy. Thus the uncertainty in the EM calculation of axisymmetric cylindrical coordinates is possible to tackle, such as the uncertainties in the calculations of lightning electromagnetic pulse, high altitude electromagnetic pulse and so on.

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“…Numerous methods for VLF waveguide propagation modeling have been developed. Lehtinen and Inan (2008) present a model using the full-wave finite element method; Chevalier and Inan (2006) and Marshall and Inan (2010) use finite difference frequency domain methods; and Thiel and Mittra (1997), Thevenot et al (1999), and Hu and Cummer (2006) each use finite difference time domain-based models. A popular EIWG modeling method is to find the dominant resonant modes in the waveguide and then relate them to the total propagated signal.…”

Section: Vlf Propagation Modelingmentioning

confidence: 99%

VLF Remote Sensing of the D Region Ionosphere Using Neural Networks

Gross

Cohen

2020

JGR Space Physics

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Narrowband very low frequency (VLF) remote sensing has proven to be a useful tool for characterizing the ionosphere's D region (60-to 90-km altitude) electron density. This work expands upon single transmitter-receiver pair electron density profile inference methods to create a more generalized narrowband VLF remote sensing method that concurrently resolves a two-parameter electron density profile for an arbitrary number of transmitter-receiver pairs. A target function is constructed to take in a single time step of narrowband amplitude and phase observations from an arbitrary number of transmitter and receiver combinations and return the inferred average waveguide parameters along all paths. The target function is approximated using an artificial neural network (ANN). Synthetic training data are generated using the U.S. Navy's Long-Wavelength Propagation Capability program, which is then used to train the ANN. Performance of the ANN with real-world data is measured in two ways. First, ANN inferred average waveguide parameters are compared to a variety of previously published narrowband VLF remote sensing experiments. Second, ANN inferred average waveguide parameters are used in Long-Wavelength Propagation Capability to predict narrowband VLF amplitude and carrier phase at a receiver that was withheld when performing the average waveguide parameter inference. Results show the approximated target function performs well in capturing temporal and spatial characteristics of the D region.

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A FDTD scheme for the computation of VLF-LF propagation in the anisotropic earth-ionosphere waveguide

Cited by 51 publications

References 8 publications

On the Accuracy of Ray‐Theory Methods to Determine the Altitudes of Intracloud Electric Discharges and Ionospheric Reflections: Application to Narrow Bipolar Events

On the Accuracy of Ray‐Theory Methods to Determine the Altitudes of Intracloud Electric Discharges and Ionospheric Reflections: Application to Narrow Bipolar Events

Stochastic FDTD for stochastic problems with axial symmetry

VLF Remote Sensing of the D Region Ionosphere Using Neural Networks

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