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Propagation and Energy Transfer
Published in James D. Taylor, Introduction to Ultra-Wideband Radar Systems, 2020
Robert Roussel-Dupré, Terence W. Barrett
The ionosphere is the charged component of the atmosphere between 70 and 1000 km. The electron density profile forms the basis for dividing the ionosphere into various layers. Figure 7.3 shows typical mid-latitude day- and nighttime profiles with the various regions identified. The term ionosphere arises in connection with the photoionization processes that create this layer. The solar EUV radiation incident on the Earth’s atmosphere is absorbed down to approximately 110 km and is primarily responsible for the formation of the ionospheric F-region (150 to 1000 km) and part of the E-region (90 to 150 km). The exponential increase in neutral density with decreasing altitude attenuates the solar EUV radiation and prevents further penetration below this altitude. The D- and lower E-regions between 70 and 110 km form by direct ionization of N2 and O2 by solar X-ray radiation and cosmic rays and by ionization of NO by solar Lyman-α radiation. The variation in ion composition with height also reflects the various dominant ionization processes (see Figure 7.2). The electron loss mechanisms that balance photoionization to produce the steady-state ionosphere include radiative recombination of O+ above 110 km and dissociative recombination of N2+, O2+, and NO+ below this altitude.
Analysis of high frequency EM-waves diffracted by a finite strip with impedance in anisotropic medium
Published in Waves in Random and Complex Media, 2021
Sajjad Hussain, Muhammad Ayub, Rab Nawaz
In many physical problems, the electromagnetic (EM) waves and acoustic waves play a vital role. Inspite of being the wave propagation in a complex phenomena, researchers have investigated the scattering of waves by considering plane waves and more physically line/point source [1–7]. The ultravoilet (UV) radiations impinging on the atmosphere of Earth causes an ionization of a fraction quantity of neutral atmosphere which results as a mixture of neutral and charged (electrons and protons) particles. This happens due to very rare collisions taking place at the altitude higher than 80 km in the atmosphere of Earth, therefore, under such circumstances the recombination process of species becomes too slow that as a result, a permanent ionized medium comes out, named as an ionosphere [8, 9]. The ionosphere has an utmost significance with regard to electromagnetic (EM) wave propagation facilitating us with a useful natural source of radio communication. The ionosphere associated with Earth has been split up into four wide regions which are D-, E-, F-region and topside region. The F-region lying above the height of 150 km is considered to be of great interest regarding radio communication [10–12]. The reason behind the F-region being of great interest is to have a significant reflecting layer for communication of signals approaching from a station on Earth. However, the ionosphere comprises of charged particles (electrons and protons) and neutral particles, that is why it may be modeled as a medium containing weak neutral plasma, therefore, the physics of ionosphere may be entitled as plasma physics. The ionosphere can be regarded as an anisotropic medium because it gets highly magnetized by Earth's magnetic field [13]. The drastic effects may happen in the measurements performed on the basis of artificial satellite located in the ionosphere while communicating to a station on Earth because the interaction of radiated signals may get modification on interaction with ionosphere as well as due to the nature of body material utilized to project the EM-signal (launched from the vehicle) to the station on Earth [14–17]. To calibrate the resulting effects appearing due to the ionosphere of plasma, Earth's magnetic field structure and natural property of material used in plate causing the diffraction of EM-signal communicating to station on Earth as well as propagating through ionosphere, a speculative model has been formulated.