Diagnostics of plasma in the ionospheric D-region: detection and study of different ionospheric disturbance types

Here we discuss our recent investigations of the ionospheric plasma by using very low and low frequency (VLF/LF) radio waves. We give a review of how to detect different low ionospheric reactions (sudden ionospheric disturbances) to various terrestrial and extra-terrestrial events, show their classification according to intensity and time duration, and present some methods for their detections in time and frequency domains. Investigations of detection in time domain are carried out for intensive long-lasting perturbations induced by solar X-ray flares and for short-lasting perturbations caused by gamma ray bursts. We also analyze time variations of signals used in the low ionospheric monitoring after earthquake events. In addition, we describe a procedure for the detection of acoustic and gravity waves from the VLF/LF signal analysis in frequency domain. The research of the low ionospheric plasma is based on data collected by the VLF/LF receivers located in Belgrade, Serbia

THE EFFECTS OF SOLAR ACTIVITY: ELECTRONS IN THE TERRESTRIAL LOWER IONOSPHERE

Solar flare X-ray energy can cause strong enhancements of the electron density in the Earth’s atmosphere. This intense solar radiation and activity can cause sudden ionospheric disturbances (SIDs) and further create ground telecommunication interferences, blackouts as well as some natural disasters and caused considerable material damage. The focus of this contribution is on the study of these changes induced by solar X-ray flares using narrowband Very Low Frequency (VLF, 3–30 kHz) and Low Frequency (LF, 30–300 kHz) radio signal analysis. The model computation and simulation were applied to acquire the electron density enhancement induced by intense solar radiation. The obtained results confirmed the successful use of applied technique for detecting space weather phenomena such as solar explosive events as well for describing and modeling the ionospheric electron density which are important as the part of electric terrestrial-conductor environment through which external-solar wind (SW) electrons can pass and cause natural disasters on the ground like fires

Chemi-ionization in Solar Photosphere: Influence on the Hydrogen Atom excited States Population

In this paper, the influence of chemi-ionization processes in $H^*(n \ge 2) + H(1s)$ collisions, as well as the influence of inverse chemi-recombination processes on hydrogen atom excited-state populations in solar photosphere, are compared with the influence of concurrent electron-atom and electron-ion ionization and recombination processes. It has been found that the considered chemi-ionization/recombination processes dominate over the relevant concurrent processes in almost the whole solar photosphere. Thus, it is shown that these processes and their importance for the non-LTE modeling of the solar atmosphere should be investigated further

Novel Modelling Approach for Obtaining the Parameters of Low Ionosphere under Extreme Radiation in X-Spectral Range

Strong radiation from solar X-ray flares can produce increased ionization in the terrestrial D-region and change its structure. Moreover, extreme solar radiation in X-spectral range can create sudden ionospheric disturbances and can consequently affect devices on the terrain as well as signals from satellites and presumably cause numerous uncontrollable catastrophic events. One of the techniques for detection and analysis of solar flares is studying the variations in time of specific spectral lines. The aim of this work is to present our study of solar X-ray flare effects on D-region using very low-frequency radio signal measurements over a long path in parallel with the analysis of X-spectral radiation, and to obtain the atmospheric parameters (sharpness, reflection height, time delay). We introduce a novel modelling approach and give D-region coefficients needed for modelling this medium, as well as a simple expression for electron density of lower ionosphere plasmas. We provide the analysis and software on GitHub

New Challenges in Exploring Solar Radiation: Influence, Consequences, Diagnostics, Prediction

The study of solar-influenced space weather and, consequently, extreme weather events, climate change, protection, and preservation are of particular interest in modern science because they are acknowledged as being important for sustainable development [...

Special Issue on Astrophysics & Geophysics: Research and Applications

The earth’s layers and space are media permanently exposed to the influences of numerous perturbations characterized by time- and space-dependent intensity. For this reason, the detection of astrophysical and terrestrial events and their influences, as well as the development and application of various models, must be based on observational data. The aim of this Special Issue, “Astrophysics & Geophysics: Research and Applications„ in Data, is to engage a wide community of scientists to reorganize and expand current knowledge in this field. This Special Issue contains five articles, which include a wide range of topics such as big data in astrophysics and geophysics, data processing, visualization and acquisition, Earth observational data, remote sensing, etc. We hope that the topic of this Special Issue of Data will be of continued interest and we look forward to seeing progress in this field

Multidisciplinarity in Research of Extreme Solar Energy Influences on Natural Disasters

The atmosphere is a very sensitive medium to extraterrestrial forces, most importantly, solar electromagnetic radiation and energetic particle intrusion. This released intense solar activity can cause sudden disturbances in the Earth’s atmosphere and further create ground telecommunication interferences, blackouts, transportation problems, water supply problems, potential health effects, as well as natural disasters, such as forest fires. These extreme events can cause billions of dollars of damage and impact individuals, families, communities, and societies. For this reason, it is of crucial importance to investigate the connections between this extreme activity and natural disasters, and further develop ways to prevent, prepare against, and respond to them. The aim of this special issue is to engage a wide community of scientists to de-fragment broaden and improve our knowledge in this field. We invite researchers from all relevant fields to publish their recent investigations in this special issue

Stark broadening of Co II spectral lines in hot stars and white dwarf spectra

International audienceStark full widths at half-maximum for 46 Co II multiplets have been calculated using modified semi-empirical method. The obtained results have been used to demonstrate the importance of Stark broadening mechanism in DA and DB white dwarf and A star atmospheres. With the obtained results we also test possibility of using some approximate methods of Stark width calculations developed on the basis of regularities and systematic trends

Response of the Earth’s Lower Ionosphere to Solar Flares and Lightning-Induced Electron Precipitation Events by Analysis of VLF Signals: Similarities and Differences

The lower ionosphere influences the propagation of electromagnetic (EM) waves, satellite and also terrestrial (anthropic) signals at the time of intense perturbations and disturbances. Therefore, data and modelling of the perturbed lower ionosphere are crucial in various technological areas. An analysis of the lower ionospheric response induced by sudden events during daytime-solar flares and during night-time-lightning-induced electron precipitation was carried out. A case study of the solar flare event recorded on 7 September 2017 and lightning-induced electron precipitation event recorded on 16 November 2004 were used in this work. Sudden events induced changes in the ionosphere and, consequently, the electron density height profile. All data are recorded by Belgrade (BEL) radio station system and the model computation is used to obtain the ionospheric parameters induced by these sudden events. According to perturbed conditions, variation of estimated parameters, sharpness and reflection height differ for analysed cases. Data and results are useful for Earth observation, telecommunication and other applications in modern society