Earth's Ionosphere Research Articles

Electron Attachment to the (O2···CO2) van der Waals Complex Results in a Monomeric Anion (O2-CO2)-, a Possible Form of CO4.

We found that electron attachment to the van der Waals complex (O2···CO2) turns the weak intermolecular bond into a pseudochemical bond of significant strength. The resulting monomeric molecular anion (O2-CO2)- may be a form of CO4-, the gaseous anionic species suspected to be present in Earth's ionosphere whose chemical characteristics have not been comprehensively identified since its existence was first predicted by Conway in 1962. The measured vertical detachment energy of CO4- is very large (4.56 ± 0.05 eV), while the known electron affinity of its component species is much smaller (0.448 eV, O2) or even negative (-0.6 eV, CO2). These characteristics are correctly borne out by theoretical calculations that show that electron attachment transforms the van der Waals complex to a single contiguous molecular anion, with the formation of a pseudochemical bond between O2 and CO2 through an extended π-orbital system.

Whistler waves produced by monochromatic currents in the low nighttime ionosphere

Abstract. We use a full-wave approach to find the field of monochromatic whistler waves, which are excited and propagating in the low nighttime ionosphere. The source current is located in the horizontal plane and can have arbitrary finite distribution over horizontal coordinates. The ground-based horizontal magnetic field and electric field at 125 km are calculated. The character of wave polarization on the ground surface is investigated. The proportion in which source energy supplies the Earth–ionosphere waveguide or flows upward can be adjusted by distribution of the source current. Received results are important for the analysis of ELF/VLF emission phenomena observed both on the satellites and on the ground.

Global Lightning Quanta

AbstractThe World Meteorological Organization recently declared lightning an essential climate variable which makes the global lightning flash rate density a key quantity, currently assessed by geostationary satellites and ground‐based lightning location networks. Yet, no theory has been put forward to explain the physical relationships between the thermodynamic temperature of the Earth’s atmosphere T, the global lightning flash occurrence frequency fg, and its radiant energy E of resonant electromagnetic waves within the Earth ionosphere cavity. These three parameters are combined here by adapting the rigorous framework of quantum physics. The minimum amount of radiant energy produced by the lightning flash occurrence frequency is the global lightning quantum E = hfg, h being Planck’s constant. The superposition of numerous global lightning quanta distributes its radiant energy around the world as Earth ionosphere cavity resonances. The novel theory is in agreement with measurements using a radiometer at Arrival Heights, Antarctica, as part of the Stanford ELF/VLF Radio Noise Survey. It is found that the measurements agree with the theory within ∼30%. The operation of the theory is illustrated with an interpretation of the measurements for an exemplary thermodynamic energy. In this case, the measurements correspond to a radiant temperature ∼−30°C akin to the mixed phase region of thunderclouds where lightning discharges are initiated. The theory can help to assess the mutual impact of climate change and global lightning on each other as proposed by the World Meteorological Organization.

Strength of the Electric Dipole Source Field in Multilayer Spherical Media

The wireless electromagnetic method (WEM) can be used to detect resources at the distances of up to 10 km underground, monitor and forecast earthquakes and fires, and study ionosphere and space weather. Based on the extremely low frequency (ELF) provided by a high-power artificial source, WEM has the advantages of strong anti-interference ability, stable signal, small measurement error, large transmitting dipole moment, and wide signal coverage. To apply the WEM to geophysical electromagnetic exploration and improve the reliability of calculation results, we study the analytical solution of the electromagnetic field in a spherical multilayer “earth–ionosphere” model, considering the displacement current in the air layer and the polarization and conductivity of the underground medium. We used Pade approximation to accelerate the numerical convergence and compare with the previous analytical and numerical results to verify the accuracy of our method. The characteristics of electromagnetic fields in different frequencies of the “earth–ionosphere” three-layer model excited by a vertical electric dipole and the influence of the earth’s conductivity on electromagnetic fields are simulated. The reasonable range of air conductivity is discussed, providing a basis for other numerical calculation methods. In contrast to the conventional electromagnetic detection methods, the electromagnetic field will vibrate in the ELF range. With decreasing underground conductivity, the electromagnetic field at the surface will gradually weaken, and the resonance phenomenon will gradually disappear, indicating that this method can be applied for the detection of underground conductivity and will further improve the detection accuracy of WEM.

Model-based reproduction and validation of the total spectra of a\xa0solar flare and their impact on the global environment at the X9.3 event of September 6, 2017

We attempted to reproduce the total electron content (TEC) variation in the Earth's atmosphere from the temporal variation of the solar flare spectrum of the X9.3 flare on September 6, 2017. The flare spectrum from the Flare Irradiance Spectral Model (FISM), and the flare spectrum from the 1D hydrodynamic model, which considers the physics of plasma in the flare loop, are used in the GAIA model, which is a simulation model of the Earth's whole atmosphere and ionosphere, to calculate the TEC difference. We then compared these results with the observed TEC. When we used the FISM flare spectrum, the difference in TEC from the background was in a good agreement with the observation. However, when the flare spectrum of the 1D-hydrodynamic model was used, the result varied depending on the presence or absence of the background. This difference depending on the models is considered to represent which extreme ultraviolet (EUV) radiation is primarily responsible for increasing TEC. From the flare spectrum obtained from these models and the calculation result of TEC fluctuation using GAIA, it is considered that the enhancement in EUV emission by approximately 15–35 nm mainly contributes in increasing TEC rather than that of X-ray emission, which is thought to be mainly responsible for sudden ionospheric disturbance. In addition, from the altitude/wavelength distribution of the ionization rate of Earth's atmosphere by GAIA (Ground-to-topside Atmosphere and Ionosphere model for Aeronomy), it was found that EUV radiation of approximately 15–35 nm affects a wide altitude range of 120–300 km, and TEC enhancement is mainly caused by the ionization of nitrogen molecules.

Deep learning for ionospheric TEC forecasting at mid-latitude stations in Turkey

Earth's ionosphere is an important medium for navigation, communication, and radio wave transmission. The inadequate advances in technology do not allow enough realization of ionosphere monitoring systems globally, and most research is still limited to local research in certain parts of the world. However, new methods developed in the field of forecasting and calculation contribute to the solution of such problems. One of the methods developed is artificial neural networks-based deep learning method (DLM), which has become widespread in many areas recently and aimed to forecast ionospheric GPS-TEC variations with DLM. In this study, hourly resolution GPS-TEC values were obtained from five permanent GNSS stations in Turkey. DLM model is created by using the TEC variations and 9 different SWC index values between the years 2016 and 2018. The forecasting process (daily, three-daily, weekly, monthly, quarterly, and semi-annual) was carried out for the prediction of the TEC variations that occurred in the first half-year of 2019. The findings show that the proposed deep learning-based long short-term memory architecture reveals changes in ionospheric TEC estimation under 1–5 TECU. The calculated correlation coefficient and R2 values between the forecasted GPS-TEC values and the test values are higher than 0.94.

How does the magnetosphere go to sleep?

Energy and circulation in the Earth's magnetosphere and ionosphere are largely determined by conditions in the solar wind and interplanetary magnetic field. When the driving from the solar wind is turned off (to a minimum), we expect the activity to die down but exactly how this happens is not known. A recent study utilized global MHD simulations to addressed the questions of what constitutes the quietest state for the magnetosphere and how it is approached following a northward turning in the IMF that minimizes the driving. An exponential decay with a decay time of about 1 h was observed in several integrated parameters related to different aspects of magnetospheric activity, including the total field-aligned current into and out of the ionosphere. The same time rate of change for the cessation of activity has also been measured in total field aligned current estimates from the AMPERE project, adding observational support to this finding. The observational study also revealed both a seasonal and a day/night variation in the decay parameter, with faster decay observed in the winter than in the summer hemisphere and on the nightside than on the dayside. Decay time averages varied between 0.8 and 2.0 h for these scenarios. The results can be understood in terms of stronger/weaker line tying of the ionospheric foot points of magnetospheric field lines for higher/lower conductivity. Additional global modeling results with varying conductance scenarios for the ionosphere confirm this interpretation and provide a quantitative understanding of the effect.

Some aspects of modulational interaction in Earth's dusty ionosphere

The development of modulational instability involving dust acoustic perturbations in dusty ionospheric plasma and in dusty plasmas of meteor tails in Earth's ionosphere was considered. The effect of collisions of electrons, ions, and dust grains with neutrals at different altitudes was estimated. It is shown that, in this case, the influence of collisions of electrons and ions with neutrals is usually less significant than the influence of collisions between dust grains and neutrals. It is demonstrated that the effect of the modulational instability on the propagation of electromagnetic waves in the dusty ionospheric plasma is the most significant at heights of 100–120 km. The values of the wave vectors of the electromagnetic pump wave at which inelastic collisions with neutrals are important for the development of modulational interaction are calculated. The modulational interaction in the dusty ionosphere is important for the explanation of different phenomena such as ground-based observations of low-frequency ionospheric radio noises with frequencies below 60 Hz. The absence of observations of low-frequency ionospheric radio noise during such phenomena as noctilucent clouds and polar mesosphere summer echoes caused by the presence of dusty plasmas at heights of 80–95 km is explained by suppression of the development of the modulational instability at these heights. The role of inelastic collisions with neutrals in meteor tails is also discussed. It is shown that for typical parameters of dusty plasmas of meteor tails such collisions do not influence the development of the modulation instability in meteor tails.

Nitric Oxide Ion Density Profiles in Earth's Nightside High‐Latitude E and F Region Ionosphere

AbstractTransport effects on nitric oxide (NO) ion density, NO+, in the presence of suprathermal electrons in the nighttime high‐latitude E and F regions of Earth's ionosphere are investigated numerically. Our model includes ion drift induced by neutral winds for the NO+. Ionization rates are obtained using a numerical Boltzmann equation solver for electron transport. Ions densities are obtained from the IRI2016 model while horizontal winds are based on observations. It is found that the altitudes where our modeled peak NO+ densities occur are in good agreement with observations. By including the radiative transfer model, local minima in NO+ density (troughs) are found to be sensitive to electron impact considered previously in chemical models.

Effects of Ion Slippage in Earth's Ionosphere and the Plasma Sheet

AbstractAlthough triggering mechanisms for substorm onsets remain highly controversial, consensus has reached that violation of frozen‐in flux condition in the central plasma sheet is required. In this study, we carry out a numerical gedanken experiment to investigate the effects of the violation by assuming ions slip with respect to the magnetic field lines in the late substorm growth phase while electrons remain magnetized, without specifying the microphysics. The simulation results predict (1) a thin arc and a strong westward electrojet associated with downward‐upward‐downward field‐aligned currents and westward‐eastward‐westward horizontal flows in the ionosphere, which are found to be consistent with a preonset arc observed by the Swarm and the all‐sky imager; (2) a rapid creation of a bubble‐blob pair in the plasma sheet with a tailward hump of Bz that may lead to tearing instability.

Time-dependent behavior of nitric oxide excited states under the effect of electron impact

At high-latitude E and F Earth's ionosphere regions and in the presence of energetic electrons, the impact of electron excitation on nitric oxide (NO) is investigated numerically. Considering an NO cross section implemented in a Boltzmann equation solver, important changes on NO* densities between nighttime and daytime are found. In addition, excited states of NO* exhibit density peaks that have a varying altitude which depends on ionospheric conditions. It is also found that the density is enhanced by solar activity and electron mean energy.

Parallel Electrical Conductivity in the Topside Ionosphere Derived From Swarm Measurements

AbstractOur knowledge of the physical properties of the topside ionosphere is still incomplete. A key point still not fully understood is how field‐aligned currents are generated, evolve and dissipate in the ionosphere. Answering to this question is fundamental for a better understanding of the mechanisms regulating the coupling between magnetosphere and ionosphere and to shed light on the physical processes inherent to space weather events occurring in the Earth's ionosphere. In this framework a relevant role is played by the ionospheric conductivity. The purpose of this study is to analyze the main properties of the electrical conductivity parallel to the geomagnetic field from a climatological point of view. The statistical study of the electrical conductivity is proposed using four years of in‐situ electron density and temperature measurements at 1 Hz acquired by the European Space Agency's Swarm A satellite. Variations due to seasonal effects are also investigated. Finally, starting from observations and comparing our results with those obtained using International Reference Ionosphere model, we give a first estimation of the conductivity mainly due to particle precipitation.

Dynamical properties of dust-ion-acoustic wave solutions in a nonextensive collisional dusty plasma

Dynamical properties of dust-ion-acoustic waves (DIAWs) are analysed in a collisional nonextensive dusty plasma composing of mobile ions, q-nonextensive electrons and stationary dust grains with slight collisions between dusts and ions. Reductive perturbation technique (RPT) is practiced to acquire the damped Korteweg-de Vries (DKdV) equation. In absence of collision between dusts and ions, the damping term vanishes and the DKdV equation reduces to the KdV equation. Bifurcation analysis of the dynamical system obtained from the KdV equation is carried out. Analytical solitary wave solution and numerical periodic wave solution of the KdV equation are presented. Approximate analytical DIAW solutions for the DKdV equation are furnished using the novel -expansion technique. As an outcome, novel approximate analytical solutions of DIAWs are obtained for the DKdV equation. The application of our work is significant to explore nonextensive plasma environment, such as, ionosphere of Earth.

НАЦИОНАЛЬНАЯ БЕЗОПАСНОСТЬ И СОЛНЕЧНО-ЗЕМНЫЕ СВЯЗИ

The paper presents the results of the analysis of scientific publications in order to identify heliogeophysical interactions and their impact on the state of biospheric processes. It is demonstrated that small disturbances in the biological environment lead to global process-es with little predictable consequences that radically change politics, economics and public health. These processes pose a serious threat to national and economic security. The studies have shown that the Earth's ionosphere is a complex dynamic system, the state of which is de-termined not only by the parameters of the atmosphere itself, but also by variations in helium and geomagnetic factors. Investigation of interrelated processes in the lower and upper lay-ers of the atmosphere is one of the priority geophysical and meteorological tasks. Key words: solar activity, heliogeophysical interactions; the Earth's magnetic field; interplanetary field; annual variations; cosmic rays.

Dispersion distortions of wide spectrum signals during their propagation in the Earth ionosphere

The current trend in the development of radio engineering systems (RES) is to use wide spectrum signals, the application of which provides an increase in the resolution and secrecy of the radar operation, an increase in the speed and volume of transmitted information for communication and telemetry systems. The class of such signals includes ultrashort pulses (USP signals), radio pulses with linear frequency modulation (chirp signals). Also of interest are ultra-wideband (UWB) noise signals (UWBN signals), which have high electromagnetic compatibility, stealth and noise immunity. When designing promising ground-based and space-based RES using wide spectrum signals, an important task is to determine the distortions of their envelope shape and distortions of spectrum, as well as the change in the polarization of the emitted wave when passing through the Earth's ionosphere, since taking these distortions into account will provide conditions for optimal reception. This article presents the numerical assessment results of the expected distortions of the wide spectrum signals main types of the decimeter wavelength range, for middle latitudes at heights from 100 km to 1000 km. The conversion of the emitted pulse into a frequency modulated radio pulse is typical for the USP signal. For a chirp radio pulse with a monotonically increasing frequency, an initial decrease in duration with an increase in amplitude and subsequent stretching in time with further spread is typical (the amplitude change is estimated due to a change in the signal shape without taking into account spread). For a chirp radio pulse with a monotonically falling frequency and a UWBN signal, dispersion distortions manifest themselves as an increase in their duration with a decrease in amplitude. For all signal types under consideration that have passed through the ionosphere, a leading edge lag is observed, the dependences of frequency on time at an altitude of 1000 km are repeated and are close to hyperbolic character, the energy spectra envelope shape of the considered signals is almost not distorted. The polarization plane rotation for signals with a spectrum concentrated in the frequency range above 0.7 GHz does not exceed 45

The PC Index Variations During 23/24 Solar Cycles: Relation to Solar Wind Parameters and Magnetospheric Disturbances

AbstractThe polar cap magnetic activity PC index is regarded as indicator of the solar wind energy that enters into the magnetosphere during the solar wind‐magnetosphere coupling (Resolutions of XXII IAGA Assembly, 2013). This study presents the results of statistical analysis of relationships between the yearly values of PC index and such indicators as the magnetic activity indices (AE and Dst), the solar wind parameters (velocity Vsw, density Nsw, dynamic pressure Pdyn, vertical interplanetary magnetic field (IMF) component Bz, total IMF field |B|, electric field EKL), and the solar activity parameters (sunspot number, coronal mass ejections, stream interaction regions) in course of 23–24 solar cycles. It is shown that the yearly values of the quiet daily curve magnitude (which serves as a level of reference in estimation of the PC index value) changed during 1998–2019 in remarkable agreement with variation of the Solar UV irradiation (150–200 nm) absorbed in the Earth's ionosphere. The yearly values of PC index perfectly correlate with the yearly values of Vsw and |B| and their product electric field EKL, as well as with the yearly values of AE and Dst indices testifying that PC index serves as the ground‐based indicator of the solar wind energy input into the magnetosphere. The yearly values of EKL, PC, AE, Dst correlate with the total IMF field |B| much better that with the IMF Bz component, testifying that efficiency of the solar wind impact on the magnetosphere is defined by the total IMF value, in contrast with Dungey's concept of reconnection.

Прискорення ресурсних випробувань полімерів космічних апаратів на стійкість до тривалої дії атомарного кисню в іоносфері Землі

The procedure of accelerated resource tests of spacecraft polymers for their resistance to the long-term influence of atomic oxygen (AO) in the Earth's ionosphere at altitudes from 200 to 700 km has been developed. The procedure involves irradiation of polymers with high-energy ions of atomic oxygen and the use of a kapton-H polyimide as reference material. The condition of equivalence of the " atomic oxygen - polymer" interaction in the ionosphere and on the laboratory set is the equality of tested material mass loss. The basis for substantiating the procedure of accelerated tests is the result: when irradiating the kapton-H polymer with high-energy atomic oxygen ions in the energy range from 30 to 80 eV, the degradation of polyimide is determined by the process of chemical etching of the material. To substantiate the procedure of accelerating resource tests of polymeric structural materials of spacecraft for resistance to long-term action of atomic oxygen flows, the dependences of mass loss and volumetric mass loss factor (reactivity) of kapton-H polyimide and Teflon FEP-100A on fluence and energy of the atomic oxygen ions have been obtained. It is shown that when irradiating kapton-H polyimide with atomic oxygen ions with the energy of 30 to 80 eV, the material mass loss due to chemical etching is about an order of magnitude greater than the mass loss due to kinetic sputtering. When the kapton-H polymer is irradiated with high-energy atomic oxygen ions, the coefficient of acceleration of the resource tests and the fluence of atomic oxygen are about two orders of magnitude greater than the coefficient of acceleration obtained using atomic oxygen ions with an energy of 5 eV.

The solar eclipse effect on diffusion processes of O+ + O2 → O2+ + O reaction for the upper ionosphere over Kharkov

The Sun is the most effective factor in determining all processes in the ionosphere. For this reason, examining the effect of solar eclipses on the earth ionosphere provides a very important source of information about sudden and medium-scale changes in the ionosphere structure during a solar eclipse. In this study, the effect of solar eclipse on March 29, 2006 in Kharkov on self-diffusion of O+ + O2 ? O2+ + O reaction was investigated depending on the altitude (202, 252, and 303 km). As a result of the investigation, the minimum value of self-diffusion coefficient was seen at three altitudes on March 29, 2006 at the time of full covering in the solar. Self-diffusion coefficients were found to increase with increasing altitude. The results of the experimental study conducted to examine the effect of the eclipse on the ionosphere using high frequency wave propagation in Turkey where it was seen total eclipse on March 29, 2006 and the result that we obtained in this research are consistent with each other.

Monitoring of Physical Processes in Upper Atmosphere, Ionosphere and Magnetosphere in Ionosphere Space Missions

The Ionosphere missions are the part of Ionosond-2025 space project, which main scientific objectives are monitoring of physical processes in the Earth upper atmosphere, ionosphere and magnetosphere, as well as of solar activity. Within the framework of the Ionozond-2025 project, it is planned to launch four spacecraft Ionosphere and one satellite Zond. The Zond satellite is planned to be launched in 2025. The main task of Zond mission is patrol of solar activity. The launch of the first pair of spacecraft is planned in early 2022, the second pair - late 2022 or early 2023. In case of successful implementation of the program of experiments on the Ionosphere satellites, control of the physical parameters of electromagnetic fields and corpuscular radiation in the near-Earth space will be provided, new information will be obtained on the geophysical processes occurring in the magnetosphere, ionosphere and upper atmosphere in their connection with solar activity.

Exploring the 21 cm cosmology: The Tianlai and Hongmeng experiments

<p indent=0mm>Since the end of the Big Bang, neutral hydrogen has been widely distributed in the universe, providing an important probe for studying the history of the universe from the dark age of the universe to cosmic dawn and reionization epoch, and then down to the post-reionization universe, and for accurately measuring the distribution of matter. But so far, due to the limitation of sensitivity, the observation of neutral hydrogen is mainly limited to the neighboring galaxies. To perform higher redshift observations, it is necessary to extract the <sc>21 cm</sc> signal from foregrounds which are several orders of magnitude stronger. This places extremely high requirements on the design of observing instrument and data processing and analysis methods. In recent years, many <sc>21 cm</sc> experiments have been built or being planned around the world, and<sc>21 cm</sc> cosmology is on the eve of a breakthrough. China has also carried out exploratory experiments on <sc>21 cm</sc> cosmology. This article presents the basic design and research progress of two such experiments: The key technology experiment of dark energy radio detection (Tianlai Experimental Array), and the Discovering Sky at the Longest wavelength (DSL) experiment, a lunar orbit radio astronomical observation array. The Tianlai Experimental Array is located at the Hongliuxia Observatory in Balikun County, Xinjiang, and it was completed in 2016. It includes a cylindrical antenna array and a dish antenna array for mid-redshift <sc>21 cm</sc> intensity mapping of large-scale structures. At present, we have conducted a preliminary analysis of the observation data and verified the calibration method and the system performance. In technology development, we are currently conducting research on the calibration of antennas with UAV; and on the science side, we will continue to improve the data processing methods, focusing on surveys of the north celestial pole region, and plan to conduct Fast Radio Burst (FRB) searches. The DSL experiment intends to launch a linear formation of satellites to fly around the moon as an array, to conduct global spectrum measurement and interferometry imaging observations. This will open up a new observation window in the electromagnetic spectrum, that is, the frequency band below 30MHz, which is difficult to observe from the ground due to the Earth ionosphere absorption, refraction and radio frequency interferences (RFI), with great potential for new discoveries of the unknown. It will also accurately measure the global spectrum under more ideal conditions, exploring the dark ages and cosmic dawn.