Does lightning causes Ionospheric Disturbances?5 answersLightning indeed causes ionospheric disturbances. Studies have shown that thunderstorm-associated lightning activities lead to significant perturbations in the ionosphere, with magnitudes of Total Electron Content (TEC) deviations reaching up to ~2.2 TECUs and dominant frequency modes falling within the gravity wave and acoustic ranges. Lightning activity has been linked to disturbances in the ionosphere, impacting Global Navigation Satellite Systems (GNSS) operations, with a notable correlation between diurnal lightning activity and ionospheric disturbances. Detrending methods like the Savitzky–Golay filter and polynomial fitting have been used to detect lightning events and assess their impact on the ionosphere, suggesting a potential association between lightning and traveling ionospheric disturbances. Furthermore, lightning discharges have been observed to cause electron heating and enhanced ionization in the ionosphere, affecting VLF communications and leading to observable ionospheric effects lasting longer than typical disturbances.
Neural network based ionosphere monitoring?5 answersNeural network-based models have been proposed for monitoring and predicting ionospheric variations. These models, such as the Enhanced Neural Network (ENN) model, Convolutional Neural Network (CNN) model, and Neural network-based model of Electron density in the Topside ionosphere (NET), have shown promising results in estimating ionospheric parameters. The ENN model outperforms traditional mathematical models in terms of accuracy and error reduction. The CNN model estimates ionospheric delay directly from GNSS observables, providing correction parameters for precise positioning services. The NET model reconstructs electron density in the topside ionosphere with high fidelity, outperforming the International Reference Ionosphere (IRI) model. These neural network-based models offer improved accuracy and can be used for real-time monitoring and forecasting of ionospheric conditions, benefiting various applications that rely on GNSS-based services.
What are the challenges in using SVC for the protection of transmission lines?5 answersThe challenges in using SVC for the protection of transmission lines include the need for fast protection systems due to the high short-circuit currents and low tolerance of power electronics to short-circuit currents. Additionally, the overcurrents and voltage drop produced by fault conditions in HVDC transmission systems can be severely dangerous to the electronic components of Voltage Source Converters (VSC). Furthermore, when series compensated transmission systems are used, challenges such as voltage inversion, current inversion, and sub-harmonic frequency oscillations arise, requiring special consideration in the protection scheme. Finally, the design of DC protection in HVDC grids is a challenge that needs to ensure transient stability of the AC/DC grid during and after DC fault interruption, while also considering system cost and security.
How does the aurora affect radio propagation?5 answersThe aurora can have profound effects on radio propagation. Disturbances in the auroral and polar-cap ionosphere can affect radio signals from ELF through VHF on terrestrial and earth-space paths, especially during sunspot maximum and disturbed periods. Turbulences of plasma caused by precipitated electrons can intensify HF radio emissions, with the predominant emissions having a frequency double that of the plasma. Transequatorial propagation on ionospheric scintillations is most likely to occur during solar maximum, particularly affecting equatorial and auroral regions. The effects of ionospheric weather on RF and GNSS systems include consequences for radio communications, space-based navigation and positioning, and surveillance. The association between the optical aurora and the effects of enhanced ionization on radio wave propagation include local absorption of radio waves, reflection from an extraordinary E-layer, scattering of radio waves, VLF radio emissions, radio noise, and polar cap absorption events.
What is Earth Ionosphere Wave Guide?5 answersThe Earth-ionosphere waveguide is a region in the Earth's atmosphere where electromagnetic waves can propagate due to the interaction between the Earth's surface and the ionosphere. It is a channel that allows for the transmission of signals over long distances. The waveguide is formed by the Earth's surface acting as a conductor and the ionosphere acting as a dielectric medium. The propagation characteristics of electromagnetic waves in the waveguide are influenced by factors such as the height of the waveguide, the conductivity of the ionosphere, and the frequency of the waves. The waveguide can have different modes of propagation, and its behavior can vary depending on the distance from the source and the presence of other factors such as the displacement current in the air.
Can electric field penetrate?7 answers