Rapid and Accurate Measurement of Polarization and Fading of Weak VHF Signals Obliquely Reflected From Sporadic-E Layers

Deacon, Chris; Witvliet, Ben A.; Steendam, Simon N.; Mitchell, Cathryn N.

doi:10.1109/tap.2020.3044654

Cited by 12 publications

(20 citation statements)

References 61 publications

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“…An empirical model of F-region irregularities was constructed by Chen et al (2017), and their model reproduces the ionospheric scintillations well and can be used to forecast global L-band scintillation. Besides, the Es layer can cause transient loss of lock of satellite signals (Yue et al, 2016) and rapid reflections of radar waves (Chris et al, 2020). The altitude-latitude distributions of Es layers (Figure 3) and the discrepancies between EsOR and EsI should provide a new perspective for the Es modeling in the future.…”

Section: Discussionmentioning

confidence: 99%

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Sporadic E (Es) layer is known as a narrow layer with dense electron density, which can occasionally occur in the E region ionosphere and severely interfere with long-distance radio communications (e.g., Chris et al, 2020;Shaikh et al, 2020;Yue et al, 2016). The observations and theoretical explanations of the characteristics of the Es layers have always been very important for space weather and navigation communication (e.g.,

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mentioning

confidence: 99%

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Altitudinal and Latitudinal Variations in Ionospheric Sporadic‐E Layer Obtained From FORMOSAT‐3/COSMIC Radio Occultation

Qiu

Yan

et al. 2021

JGR Space Physics

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Sporadic E (Es) layers are known for their layered structures with enhanced electron density. Recently, some scientists have studied the relationship between the occurrence rate and intensity of the Es layer in the global distribution. However, the relationship between the Es layer parameters (Es layer occurrence rate, Es layer intensity, Es layer thickness) in the vertical direction seems to be ignored to date. This paper highlights the vertical profiles of the occurrence rate, intensity, and thickness of the Es layers by using scintillation index (S4) from FORMOSAT‐3/COSMIC satellites from July 2007 to March 2015. The results show that there are some persistent differences between the occurrence rate, intensity, and thickness of the Es layers in the vertical profiles, which is different from their general similarity in the latitude distribution. It is found that the Es layer occurrence rate has a maximum value at ∼102 km altitude, but the Es layer intensity and Es layer thickness reach their maximum at an altitude of ∼110 km. Besides, the intensity and thickness of the Es layer exhibit a high linear relationship, which suggests that the larger electron density of the Es layer, the thicker its thickness. The Horizontal Wind Model (HWM14) indicates that the latitudinal variations in Es layers parameters are highly coincident with the zonal wind shear. However, the altitudinal variations in Es layers parameters do not agree well with the zonal wind shear.

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Section: Discussionmentioning

confidence: 99%

“…

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mentioning

confidence: 99%

Altitudinal and Latitudinal Variations in Ionospheric Sporadic‐E Layer Obtained From FORMOSAT‐3/COSMIC Radio Occultation

Qiu

Yan

et al. 2021

JGR Space Physics

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“…The axial ratio is defined to be positive when the sense of rotation is right-handed, and negative when the sense of rotation is left-handed. Following the IEEE conventions, it can be shown [34,35] that, for the axial ratio ar and tilt angle τ of the polarization ellipse [21]:…”

Section: Characterization Of Polarization Statementioning

confidence: 99%

Evidence for the Magnetoionic Nature of Oblique VHF Reflections from Midlatitude Sporadic-E Layers

Deacon¹,

Mitchell²,

Watson³

et al. 2022

Preprint

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Mid-latitude sporadic-E (Es) is an intermittent phenomenon of the lower E region of the ionosphere. Es clouds are thin, transient, and patchy layers of intense ionization, with ionization densities which can be much higher than in the background ionosphere. Oblique reflection of radio signals in the very high frequency (VHF) range is regularly supported, but the mechanism for it has never been clearly established - specular reflection, scattering, and magnetoionic double refraction have all been suggested. This article proposes using the polarization behaviour of signals reflected from intense midlatitude sporadic-E clouds as an indicator of the true reflection mechanism. Results are presented from a measurement campaign in the summer of 2018, which gathered a large amount of data at a receiving station in the UK using 50 MHz amateur radio beacons as signal sources. In all cases the signals received were elliptically polarized, despite being transmitted with linear polarization; there were also indications that polarization behaviour varied systematically with the orientation of the path to the geomagnetic field. This represents, for all the examples recorded, clear evidence that signals were reflected from midlatitude Es by magnetoionic double refraction.

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“…The ionospheric sporadic E (Es) layer is a thin and dense electron density layer that occasionally appears at altitudes between 95 and 125 km, which can significantly affect the performance of radio communication and navigation systems (e.g., Deacon et al., 2020; Hosokawa et al., 2021; Sakai et al., 2018; Whitehead, 1960; Yue et al., 2016). Es layers usually have a thickness of 1–5 km (Qiu, Yu, et al., 2021; Tsai et al., 2018; Zeng & Sokolovskiy, 2010) and a horizontal extent of 50–3,000 km (Maeda & Heki, 2015; Sun et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

Qiu,

Yamazaki,

et al. 2023

JGR Space Physics

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In previous studies, various physical parameters, such as vertical wind shear null, vertical ion velocity null (IVN), and maximum gradient of vertical ion velocity, have been used as an indicator of Es layer height in light of the wind shear theory. Using a numerical Es layer model, we investigated which parameter represents the height of Es layer over Wuhan (114.4°E, 30.5°N) most precisely. The simulation results show that the height of Es layer above 110 km depends most strongly on the height of vertical IVN. However, below 110 km, the height of vertical IVN does not always agree with the height of Es layer. The analysis of simulation results suggests that the vertical gradient of the ratio of the ion‐neutral collision frequency (νi) to the ion gyrofrequency (ωi) affects the Es layer formation at lower altitudes (below 110 km). We also examined the effect of electric fields on the height and intensity of Es layers over Wuhan. It is found that eastward/upward electric fields can lift the Es layer height and reduce the Es layer intensity.

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Rapid and Accurate Measurement of Polarization and Fading of Weak VHF Signals Obliquely Reflected From Sporadic-E Layers

Cited by 12 publications

References 61 publications

Altitudinal and Latitudinal Variations in Ionospheric Sporadic‐E Layer Obtained From FORMOSAT‐3/COSMIC Radio Occultation

Altitudinal and Latitudinal Variations in Ionospheric Sporadic‐E Layer Obtained From FORMOSAT‐3/COSMIC Radio Occultation

Evidence for the Magnetoionic Nature of Oblique VHF Reflections from Midlatitude Sporadic-E Layers

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

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