Heliogeophysical Conditions Research Articles

Автоматическая интерпретация ионограмм наклонного зондирования на основе гибридных алгоритмов

The paper presents a method of interpreting data on oblique ionosphere sounding (OS) with a continuous chirp signal. Hybrid algorithms for automatic interpretation of ionograms by selected points with significant amplitude obtained during secondary data processing for various heliogeophysical conditions have been developed and implemented. For the conditions of the two-layer ionosphere, an interpretation method has been worked out which involves analyzing histograms for the distribution of points with significant amplitude, which fall into a model mask constructed from the results of modeling of the distance-frequency characteristic for propagation when it moves over the ionogram. For the multilayer ionosphere, the interpretation is based on the study of the ionogram amplitude relief. The algorithms for extracting tracks of signals reflected from sporadic layers are examined separately. We report the results of interpretation of ionograms obtained on the network of chirp sounding radio paths in the northeastern region of Russia.

Automatic interpretation of oblique sounding ionograms based on hybrid algorithms

The paper presents a method of interpreting data on oblique ionosphere sounding (OS) with a continuous chirp signal. Hybrid algorithms for automatic interpretation of ionograms by selected points with significant amplitude obtained during secondary data processing for various heliogeophysical conditions have been developed and implemented. For the conditions of the two-layer ionosphere, an interpretation method has been worked out which involves analyzing histograms for the distribution of points with significant amplitude, which fall into a model mask constructed from the results of modeling of the distance-frequency characteristic for propagation when it moves over the ionogram. For the multilayer ionosphere, the interpretation is based on the study of the ionogram amplitude relief. The algorithms for extracting tracks of signals reflected from sporadic layers are examined separately. We report the results of interpretation of ionograms obtained on the network of chirp sounding radio paths in the northeastern region of Russia.

Statistical models of the variability of plasma in the topside ionosphere: 2. Performance assessment

Statistical models of the variability of plasma in the topside ionosphere based on the Swarm data have been developed in the “Swarm Variability of Ionospheric Plasma” (Swarm-VIP) project within the European Space Agency’s Swarm+4D-Ionosphere framework. The models can predict the electron density, its gradients for three horizontal spatial scales – 20, 50 and 100 km – along the North-South direction and the level of the density fluctuations. Despite being developed by leveraging on Swarm data, the models provide predictions that are independent of these data, having a global coverage, fed by various parameters and proxies of the helio-geophysical conditions. Those features make the Swarm-VIP models useful for various purposes, which include the possible support for already available ionospheric models and proxy of the effect of ionospheric irregularities of the medium scales that affect the signals emitted by Global Navigation Satellite Systems (GNSS). The formulation, optimisation and validation of the Swarm-VIP models are reported in Paper 1 (Wood et al. 2024. J Space Weather Space Clim. in press). This paper describes the performance assessment of the models, by addressing their capability to reproduce the known climatological variability of the modelled quantities, and the ionospheric weather as depicted by ground-based GNSS, as a proxy for the ionospheric effect on GNSS signals. Additionally, we demonstrate that, under certain conditions, the model can better reproduce the ionospheric variability than a physics-based model, namely the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM).

Accuracy of hmF2 estimations, including IRI-2020 options and ionograms validated parameters, compared to ISR measurements at Millstone Hill

Several empirical formulations used over time to estimate the fundamental ionospheric parameter hmF2 have been compared in this study. These are the first formulation proposed by Shimazaki (1955) (SHI-1955) as a function of the propagation parameter M(3000)F2, the more accurate BSE-1979 formula proposed by Bilitza et al. (1979) and firstly adopted by the International Reference Ionosphere (IRI) model, and the newest Altadill-Magdaleno-Torta-Blanch (AMTB-2013) (Altadill et al., 2013) and SHU-2015 (Shubin, 2015) models, obtained with a different approach with no explicit dependence on any ionospheric parameter and added as alternative options in the IRI-2016. The evaluation of the accuracy of the available formulation is performed by comparing the modeled values of hmF2 with those simultaneously obtained with independent measurements from the Incoherent Scatter Radar (ISR) installed at the Millstone Hill ionospheric station. The database considered consists of 3626 measurements, thus allowing the evaluation of the results for different heliogeophysical conditions. SHI-1955 and BSE-1979 formulations are evaluated also using input data manually scaled from ionograms recorded at the same location, with the aim of evaluating their accuracy when updated with validated data rather than modeled ones. The SHU-2015 is confirmed the best option in any condition, while AMTB-2013 turns out to perform poorly during night, when SHI-1955 and BSE-1979 fed by validated data can be used for trend analyses due to the high correlation with ISR data. Despite this, BSE-1979 performs better with modeled parameters as input, in terms of RMSE and mean deviation from ISR data. The use of SHI-1955 with CCIR-modeled M(3000)F2 is discouraged under daytime conditions even for long trend analyses.

Heliogeophysical Conditions in Moscow during the Covid-19 Pandemic

Heliogeophysical Conditions in Moscow during the Covid-19 Pandemic

Morphological features of heliogeophysical conditions leading to the appearance of geomagnetically induced currents on the territory of Kazakhstan

Morphological features of helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes are determined. Using the example of a very large geomagnetic storm with a sudden onset that occurred on May 10-15, 2021, the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes are described. To describe this heliogeophysical event, satellite observations with high time resolution (5 minutes) for various parameters of the solar wind, data on interplanetary and geomagnetic indices were used. Geomagnetically induced currents can be introduced into the network and cause many adverse consequences. The vulnerability of major electric power systems to such events has increased over the past few decades as the transmission lines of the power grid have become more interconnected and increased in length. In this paper, the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at middle latitudes are determined. Thus, using the example of a very large geomagnetic storm with a sudden onset that occurred on May 10-15, 2021, a description is given of the morphological features of the helio-geophysical conditions leading to the appearance of geomagnetically induced currents at mid-latitudes.

Comparative analysis of variations in the critical frequency of the ionospheric F2 layer under different heliogeophysical conditions at the Moscow station

Results of the statistical analysis of variations of critical frequency of a layer of F2 of an ionosphere at various levels of solar and geomagnetic activity are presented by data from the station Moscow from 1957 to 2019. Optimum intervals of division into levels of geomagnetic activity are experimentally found. The need to divide solar activity into low and high in ionospheric research has been proved. The effect of solar and geomagnetic activity on the occurrence of periodic positive and negative deviations of the critical frequency of the ionosphere F2 layer from the median, calculated for 27 previous days in various seasons, is shown. It has been shown that the daily course of deviations at a high level of geomagnetic activity for negative deviations ceases to be pronounced, unlike positive deviations.

Modeling of the Lower Ionosphere During Solar X‐Ray Flares of Different Classes

AbstractThis study presents the results obtained from modeling the lower ionosphere response to C‐, M‐ and X‐class solar X‐ray flares. This model is based on a 5‐component scheme for the ionization‐recombination cycle of the ionospheric D‐region. Input parameters for the plasma‐chemical model under different heliogeophysical conditions corresponding to selected X‐ray flares were determined by using data received from the AURA, SDO, and GOES satellites. Verification of the obtained results was carried out with use of ground‐based radiophysical measurements taken at the geophysical observatory Mikhnevo. The results obtained from a comparison of the calculated and experimental radio wave amplitude variations along six European very low frequency (VLF) paths show that the average normalized root mean square error is ∼7%, 14%, and 18% for C‐, M‐, and X‐class flares, respectively. Qualitative and quantitative analysis of the verification results for the VLF signal amplitude show good predictive capability of the model built for describing weak and moderate ionospheric disturbances.

АЛГОРИТМ ТРАЕКТОРНОЙ ОБРАБОТКИ ИНФОРМАЦИИ РАДИОЛОКАЦИОННЫХ ИЗМЕРИТЕЛЬНЫХ КОМПЛЕКСОВ НА ОСНОВЕ КЛАСТЕРИЗАЦИИ МЕТОДОМ K-MEANS

The problem situation caused by the need to improve the accuracy of determining the location of observed space objects by radar measuring complexes is considered. It is shown that the accuracy characteristics of radar measuring systems depend on the contribution of various measurement errors, the most significant of which for modern highly informative observation tools are atmospheric, determined by helio-geophysical conditions of operation. It is noted that the currently applied approaches to compensation of atmospheric measurement errors do not allow taking into account the heliogeophysical conditions of operation of radar measuring complexes with high time and spatial resolution. It is shown that when processing coordinate information, sporadic changes in heliogeophysical operating conditions are not fully taken into account, which leads to an increase in errors in measuring the location of space objects and a decrease in the information capabilities of radar measuring complexes. The idea of using the discrepancy of measurements by the radar measuring complex of the location of space objects for which there is a priori coordinate information is considered. The results of combining groups of space object location measurements using cluster analysis methods are shown. The results of computer modeling are presented and it is shown that the proposed approach allows us to determine the areas where the influence of heliogeophysical conditions increases the measurement errors. The main calculation relations are described and the stages of the algorithm for trajectory processing of information from radar measuring complexes based on clustering by the K-MEANS method are shown. Further directions of using the results of the algorithm are proposed, which con sist in using data on formed clusters for processing information about space objects for which there is no a priori coordinate information. It is shown that the proposed approach can be applied in order to improve the information capabilities of radar measuring systems.

Validation of NeQuick 2 Model Topside Ionosphere and Plasmasphere Electron Content Using COSMIC POD TEC

AbstractAn accurate representation of the topside ionosphere and plasmasphere electron content is still one of the important issues for ionospheric models, particularly for those used in GNSS applications. In this work, a validation of NeQuick 2 empirical ionospheric model has been performed in terms of ionosphere topside and plasmasphere electron content in the altitude range ~800–20,200 km. For this purpose, total electron content (TEC) data derived from precise orbit determination (POD) antennas onboard COSMIC low earth orbit (LEO) satellites tracking GPS signals have been used. The data span the period from 2006 to 2018 and correspond to different heliogeophysical conditions. In order to remove unrealistic TEC values from the validation process, a specific filtering procedure has been applied to POD‐derived TEC data. Subsequently, the statistical analysis of the difference between the modeled and the corresponding experimentally derived TEC values has been performed on data obtained during geomagnetically quiet periods. The results are presented as a function of solar activity level, season, local time, and geomagnetic latitude plots. They show that NeQuick 2 model underestimates the ionosphere topside and plasmasphere electron content, particularly during the early morning hours. The conditions under which the discrepancy between the model and experimental data is the highest have been also identified and considered as indications for future model improvements.

Global Dynamic Model of Critical Frequency of the Ionospheric F2 Layer

A global dynamic model of the F2 layer of the ionosphere GDMF2 is designed to calculate foF2 in both quiet and geomagnetically disturbed conditions. The term “dynamic model” implies that the change in foF2 at middle, subauroral, and auroral latitudes depends on the current level of geomagnetic activity with consideration of the prehistory of its development. A distinctive feature of this model is the empirical approach used to create the median (background) model of foF2 for quiet geomagnetic conditions and a number of aeronomic corrections to it related to the formation of the main ionospheric trough and the auroral peak of electron density, as well as changes in the temperature and composition of the thermosphere. All of these corrections depend on the changes in the heliogeophysical conditions. The global dynamic foF2 model demonstrates considerable improvement as compared to IRI-2016 (with the option ‘STORM = ON’) by on average of ~16% at high and middle and ~7% at equatorial latitudes.

Постнатальное становление иммуннофизиологического статуса свиней в гелиогеофизических условиях региона

Постнатальное становление иммуннофизиологического статуса свиней в гелиогеофизических условиях региона

The ionospheric irregularities climatology over Svalbard from solar cycle 23

The paper presents an unprecedented description of the climatology of ionospheric irregularities over the Arctic derived from the longest Global Navigation Satellite Systems data series ever collected for this specific aim. Two TEC and scintillation receivers are working at Ny-Ålesund (Svalbard, NO), the first of which has been installed in late September 2003. They sample the L1 and L2 signals at 50 Hz from all the GPS satellites in view. The receivers monitor an area of about 600 km radius that includes the auroral and cusp/cap regions in the European longitudinal sector. The length of the data series and the privileged site of observation allow describing the Arctic ionosphere along about two solar cycles, from the descending phase of cycle 23 to almost the end of cycle 24. Our analysis results into a detailed assessment of the long-term behaviour of the ionosphere under solar maximum and solar minimum conditions, including several periods of perturbed ionospheric weather caused by unfavourable helio-geophysical conditions. Since November 2015, a multi-constellation GNSS receiver has been deployed in Ny-Ålesund, providing the opportunity to perform the ionospheric climatology from Galileo signals. The results offer realistic features of the high latitude ionosphere that can substantially contribute to the necessary improvements of forecasting models, providing a broad spectrum of ionospheric reactions to different space weather conditions.

Real‐Time Techniques for Interpretation of Ionospheric Backscatter Sounding Data

AbstractWe present techniques and algorithms for automatic processing and interpretation of data of ionospheric backscatter sounding (BS) using a continuous chirp signal. Experimental ionograms are processed based on data filtration with further compression using the cellular automaton method. Interpretation of signals in a backscatter ionogram is carried out by calculating the backscatter leading edge. Slightly changing ratios of frequency dependences for group characteristics of oblique sounding and BS signals in various heliogeophysical conditions are used. Parameters of radio wave propagation are calculated within the waveguide approach using the International Reference Ionosphere model. The results of interpretation for a BS ionogram allow quick determination of maximum usable frequencies, from which characteristics of oblique sounding signals are corrected for given radio paths in the sounding sector of interest.

Численное моделирование параметров полярной ионосферы

В статье дается обзор разработанных трех численных моделей для расчета электродинамических параметров высокоширотной ионосферы Земли. Модель глобального распределения ионосферного электрического потенциала, построенная на основе решения краевой задачи о растекании ионосферных токов, позволяет рассчитать траектории конвекции ионосферной плазмы в северном и южном полушариях. Модель высокоширотной ионосферы позволяет оперативно рассчитывать трехмерную структуру электронной плотности в диапазоне высот 120-500 км при различных гелио-геофизических условиях. Учитывается определяющая роль электрических полей магнитосферного происхождения. Концентрация основных ионосферных ионов определяется решением уравнения фотохимического баланса и конвективно-диффузионного уравнения вдоль траектории конвекции плазменных трубок с учётом параметров термосферы. Разработана методика и алгоритмы численного расчета распределения магнитного поля над ионосферой, которое создается электрическими токами магнитосферного происхождения. Модель базируется на решении уравнения для векторного магнитного потенциала и позволяет рассчитать двумерную картину магнитных вариаций.

Assessment of the Accuracy of Calculations Using the International Reference Ionosphere Model IRI-2016: I. Electron Densities

The paper quantitatively compares the results of calculations of the electron density Ne by the International Reference Ionosphere model IRI-2016 with experimental data obtained from the DE-2 satellite. It considers 648 variants of heliogeophysical conditions. The deviation of theoretical estimates from experimental values is within the instrumental accuracy of satellite data in an average of 27% of cases. It is concluded that the IRI-2016 model, the approximation coefficients of which in functional dependences are associated with heights of the F-region, gives negative values of the efficiency coefficient of the predicted electron density in ~73% of cases in the outer ionosphere at altitudes over 500 km.

SibNet — Siberian Global Navigation Satellite System Network: Current state

In 2011, ISTP SB RAS began to deploy a routinely operating network of receivers of global navigation satellite system signals. To date, eight permanent and one temporal sites in the Siberian region are operating on a regular basis. These nine sites are equipped with 12 receivers. We use nine multi-frequency multi-system receivers of Javad manufacturer, and three specialized receivers NovAtel GPStation-6 designed to measure ionospheric phase and amplitude scintillations. The deployed network allows a wide range of ionospheric studies as well as studies of the navigation system positioning quality under various heliogeophysical conditions. This article presents general information about the network, its technical characteristics, and current state, as well as the main research problems that can be solved using data from the network.

Сибирская сеть приемников сигналов глобальных навигационных спутниковых систем SibNet: текущее состояние

In 2011, ISTP SB RAS began to deploy a routinely operating network of receivers of global navigation satellite system signals. To date, eight permanent and one temporal sites in the Siberian region are operating on a regular basis. These nine sites are equipped with 12 receivers. We use nine multi-frequency multi-system receivers of Javad manufacturer, and three specialized receivers NovAtel GPStation-6 designed to measure ionospheric phase and amplitude scintillations. The deployed network allows a wide range of ionospheric studies as well as studies of the navigation system positioning quality under various heliogeophysical conditions. This article presents general information about the network, its technical characteristics, and current state, as well as the main research problems that can be solved using data from the network.

Анализ результатов расчетов концентрации электронов по детерминированно-вероятностной модели среднеширотной невозмущенной D-области ионосферы

The work is devoted to the development of a fundamentally new way of modeling the ionospheric D-region — deterministic-probabilistic. The results of electron density (Ne) calculations using this technique are analyzed. Research of this kind is of fundamental importance, related to the rejection of a purely deter-ministic description of a continuously changing envi-ronment such as the ionosphere. In this work, Ne is cal-culated using a five-component system of ionization-recombination cycle equations. Probability density functions (PDFs) of input parameters of the model are used to solve the system. The most important sources of the D-region ionization are taken into account to calculate PDFs of the ionization rate. The necessary number of iterations is determined by the convergence of PDFs of the electron density from 50 to 85 km at midlatitudes under different heliogeophysical conditions. Theoretical Ne PDFs have been shown to be in good agreement with two experimental databases on electron density, especially at large D-region heights. The next important stage of modeling is the thorough verification of PDFs from experimental radiophysical data on VLF—LF propagation.

Analysis of electron density calculations using deterministic-probabilistic model of the ionospheric D-region

The work is devoted to the development of a fundamentally new way of modeling the ionospheric D-region – deterministic-probabilistic. The results of Ne calculations using this technique are analyzed. Research of this kind is of fundamental importance, related to the rejection of a purely deterministic description of a continuously changing environment such as the ionosphere. In this work, the electron density is calculated using a five-component system of ionization-recombination cycle equations. Probability density functions (PDFs) of input parameters of the model are used to solve the system. The most important sources of the D-region ionization are taken into account to calculate PDFs of the ionization rate. The necessary number of iterations is determined by the convergence of PDFs of the electron density from 50 km to 85 km at midlatitudes under different heliogeophysical conditions. Theoretical Ne PDFs have been shown to be in good agreement with two experimental databases on electron density, especially at large D-region heights. The next important stage of modeling is the thorough verification of Ne PDFs from experimental radiophysical data on VLF–LF propagation.