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28 pages, 3072 KiB

Open AccessEditor’s ChoiceArticle

HF-Induced Artificial Injection of Energetic Electrons from the Earth’s Radiation Belt as a Powerful Source for Modification of Ionized and Neutral Components of the Earth’s Atmosphere

by Vladimir L. Frolov and Arkady V. Troitsky

Atmosphere 2023, 14(5), 843; https://doi.org/10.3390/atmos14050843 - 9 May 2023

Cited by 9 | Viewed by 2481

Abstract

It has been found in experiments at the SURA mid-latitude heating facility that the modification of the ionospheric F₂ layer by powerful HF radio waves gives rise to artificial injection of energetic electrons from the Earth’s radiation belt into the atmosphere. The spectral, energy, and spatial characteristics of such an injection are presented in the paper. It is significant that the energetic electrons excite the atoms and molecules of the atmosphere to Rydberg energy levels, followed by the transition of the excited atoms and molecules to lower energy states, accompanied by the radiation of the microwave electromagnetic emissions. It has been shown that the artificial injection of energetic electrons can be considered as an independent powerful source of generation of secondary artificial turbulence, the effect of which manifests itself at ionospheric and mesospheric heights both near the heating facility and at a large distance from it up to a thousand or more kilometers. Examples of such generation are given. Full article

(This article belongs to the Special Issue Geomagnetic Storms and Their Influence on Atmosphere–Ionosphere Coupling)

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15 pages, 12331 KiB

Open AccessTechnical Note

A Proposal for Modification of Plasmaspheric Electron Density Profiles Using Characteristics of Lightning Whistlers

by Desy Purnami Singgih Putri, Yoshiya Kasahara, Mamoru Ota, Shoya Matsuda, Fuminori Tsuchiya, Atsushi Kumamoto, Ayako Matsuoka and Yoshizumi Miyoshi

Remote Sens. 2023, 15(5), 1306; https://doi.org/10.3390/rs15051306 - 26 Feb 2023

Cited by 4 | Viewed by 2002

Abstract

Reconstruction of reliable plasmaspheric electron density profiles is important for understanding physical processes in the plasmasphere. This paper proposes a technique that can be applied to correct the plasmaspheric electron density profiles using ray tracing by scrutinizing dispersion analyses of lightning whistlers. The Global Core Plasma Model and the International Reference Ionosphere were introduced as a reference electron density profile. Modifications of this electron density profile were then proposed to satisfy the dispersion characteristics of lightning whistlers measured by satellites in the plasmasphere. We first introduce two kinds of functions to modify the electron density: constant and linear, the linear function is more adequate. We applied our method to two lightning whistler events on 14 August 2017, measured by the Plasma Wave Experiment/Waveform Capture aboard the Arase satellite, and analyzed the dispersion of the observed lightning whistlers. We show how the density modification affects the delay time of the ray path and satisfies the dispersion characteristics under the appropriate adjustments. Full article

(This article belongs to the Special Issue Satellite Measurements and the Monitoring of Ionosphere and Space Weather)

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18 pages, 6538 KiB

Open AccessArticle

HF-Induced Modifications of the Electron Density Profile in the Earth’s Ionosphere Using the Pump Frequencies near the Fourth Electron Gyroharmonic

by Alexey V. Shindin, Evgeny N. Sergeev, Savely M. Grach, Gennady M. Milikh, Paul Bernhardt, Carl Siefring, Michael J. McCarrick and Yulia K. Legostaeva

Remote Sens. 2021, 13(23), 4895; https://doi.org/10.3390/rs13234895 - 2 Dec 2021

Cited by 2 | Viewed by 2177

Abstract

We discuss results on plasma density profile modifications in the F-region ionosphere that are caused by HF heating with the frequency f₀ in the range [(−150 kHz)–(+75 kHz)] around the fourth electron gyroharmonic 4f_c. The experiments were conducted at the HAARP facility in June 2014. A multi-frequency Doppler sounder (MDS), which measures the phase and amplitude of reflected sounding radio waves, complemented by the observations of the stimulated electromagnetic emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave and from the upper hybrid region, where the expulsion from the latter was strongly suppressed for f₀ ≈ 4f_c. The plasma expulsion from the upper hybrid region was accompanied by the sounding wave’s anomalous absorption (AA) slower development for f₀ ≈ 4f_c. Furthermore, slower development and weaker expulsion were detected for the height region between the pump wave reflection and upper hybrid altitudes. The combined MDS and SEE allowed for establishing an interconnection between different manifestations of the HF-induced ionospheric turbulence and determining the altitude of the most effective pump wave energy input to ionospheric plasma by using the dependence on the offset between f₀ and 4f_c. Full article

(This article belongs to the Special Issue Space Geodesy and Ionosphere)

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10 pages, 38463 KiB

Open AccessArticle

The Apparent Behavior of Electron Density during an Alternating O/X-Mode Heating Experiment

by Zeyun Li, Qingfeng Li, Hanxian Fang and Hongwei Gong

Universe 2021, 7(8), 274; https://doi.org/10.3390/universe7080274 - 28 Jul 2021

Cited by 1 | Viewed by 1605

Abstract

We present the observations of the artificial ionospheric modification experiment of EISCAT on 18 October 2012 in Tromsø, Norway. When the pump of alternating O mode and X mode is switched on, the UHF radar observation shows some strong enhancements in electron density, ion lines and plasma lines. Based on some existing theories, we find the following: First, during the experiment, the frequency of plasma line (

f_{L}

), ion line (

f_{i a}

) and pump (

f_{h}

) matches

f_{L}

f_{h}

− 3

f_{i a}

and =

f_{h}

− 5

f_{i a}

occasionally demonstrated that the cascade process occurred. Second, through quantitative calculation, we found that the O-mode component mixed in X-mode wave satisfies the thresholds of the parametric decay instability and the oscillation two-stream instability, from which we infer that the HF-induced plasma lines (HFPLs) and HF-enhanced ion lines (HFILs) observed in X-mode pulse could have been caused by the O-mode component mixed in X-mode wave. Third, the UHF radar observation shows some apparent enhancements over a wide altitude range (from approximately the reflection altitude to ~670 km) in electron density during X-mode pulse, which also does not, in fact, correspond to a true increase in electron density, but due to the enhancement in ion line or the enhancement in radar backscatter induced by some unknown mechanism. Full article

(This article belongs to the Section Space Science)

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