Changes In Solar Activity Research Articles

Sensitivity of Global Oscillation Frequencies to Solar Activity on Short Timescales

Sun’s oscillations frequencies vary with the changing magnetic activity and hold a strong positive correlation. While most of the analysis for global modes have been carried out using time series longer than a solar rotation, only a few studies are available showing their variation on shorter timescales. Using Doppler observations from Global Oscillation Network Group during the period 1995–2024, we analyze oscillation frequencies computed on a timescale of nine days and compare them with those obtained from 108 days. We also study their sensitivity in cycles 23 and 24 to the change in solar activity as represented by the 10.7 cm radio flux.

Role of Squalene Epoxidase Gene (SQE1) in the Response of the Lichen Lobaria pulmonaria to Temperature Stress.

Currently, due to the increasing impact of anthropogenic factors and changes in solar activity, the temperature on Earth is rising, posing a threat to biodiversity. Lichens are among the most sensitive organisms to climate change. Elevated ambient temperatures can have a significant impact on lichens, resulting in more frequent and intense drying events that can impede metabolic activity. It has been suggested that the possession of a diverse sterol composition may contribute to the tolerance of lichens to adverse temperatures and other biotic and abiotic stresses. The major sterol found in lichens is ergosterol (ERG); however, the regulation of the ERG biosynthetic pathway, specifically the step of epoxidation of squalene to 2,3-oxidosqualene catalyzed by squalene epoxidase during stress, has not been extensively studied. In this study, we used lichen Lobaria pulmonaria as a model species that is well known to be sensitive to air pollution and habitat loss. Using in silico analysis, we identified cDNAs encoding squalene epoxidase from L. pulmonaria, designating them as LpSQE1 for the mycobiont and SrSQE1 for the photobiont Symbiochloris reticulata. Our results showed that compared with a control kept at room temperature (+20 °C), mild temperatures (+4 °C and +30 °C) did not affect the physiology of L. pulmonaria, assessed by changes in membrane integrity, respiration rates, and PSII activity. An extreme negative temperature (-20 °C) noticeably inhibited respiration but did not affect membrane stability. In contrast, treating lichen with a high positive temperature (+40 °C) significantly reduced all physiological parameters. Quantitative PCR analysis revealed that exposing thalli to -20 °C, +4 °C, +30 °C, and +40 °C stimulated the expression levels of LpSQE1 and SrSQE1 and led to a significant upregulation of Hsps. These data provide new information regarding the roles of sterols and Hsps in the response of lichens to climate change.

Vegetation, temperature, and Indian Summer Monsoon evolution over the past 4400 years revealed by a pollen record from Drigo Co on the southern Qinghai-Tibet Plateau

Understanding the changes in temperature and precipitation on the southern Qinghai-Tibet Plateau (QTP), which is influenced by the Indian Summer Monsoon (ISM), is crucial for predicting possible future changes in the regional ecological environment under ongoing climate change. However, due to the lack of well-dated, high-resolution paleoclimate records, the trends of temperature and ISM precipitation on the southern QTP since the mid-Holocene are poorly understood. We present a high-resolution pollen record from Dirgo Co, on the southern QTP, spanning the past 4400 years. The decrease in the pollen ratio of Artemisia to Cyperaceae (A/Cy) indicates a downward shift of altitudinal vegetation belts in the Drigo Co area over the past 4400 years, suggesting falling temperatures; and decreases in tree pollen percentages indicate the gradual weakening of the ISM. Our pollen record also indicates five cold phases with the near-simultaneous weakening of the monsoon, during: 4300–4100 cal yr BP, 3600–3400 cal yr BP, 2800–2600 cal yr BP, 1600–1400 cal yr BP, and 700–100 cal yr BP, and these climate anomalies were also recorded elsewhere on the QTP. We suggest that the changes in temperature and ISM intensity on the southern QTP over the past 4400 years were modulated by changes in summer insolation and solar activity. These changes affected the sea surface temperature (SST) over the tropical Pacific and Indian Ocean regions, and they were linked to a positive phase of the El Niño/Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), which weakened the ISM intensity in the Drigo Co area. Additionally, due to increased evaporation related to high temperatures, combined with intensified grazing activities over the past ∼200 years, the lake level has fallen, and the vegetation cover has decreased. As global temperatures continue to rise, the alpine steppe in the Drigo Co area may increase and the vegetation density may gradually decrease, and at the same time the regional ecological environment may gradually deteriorate.

The Response of Stratospheric Gravity Waves to the 11-Year Solar Cycle

Atmospheric gravity waves are one of the important dynamic processes in near space and are widely present in the atmosphere. They play a crucial role in the transfer of energy and momentum between different regions of the atmosphere. The Sun, as the ultimate source of gravity wave energy, significantly influences the intensity of gravity wave disturbances through its activity variations. This paper utilizes data from the Global Navigation Satellite System Occultation Sounder (GNOS) onboard the Fengyun-3C (FY-3C) satellite to invert global stratospheric gravity wave disturbances. It provides the global stratospheric gravity wave distribution from 2015 to 2023, nearly covering one solar activity cycle, and focuses on analyzing the response of gravity waves at different latitudes, altitudes, and wavelengths to the solar activity cycle. We found that short-wavelength gravity waves respond more noticeably to solar activity compared to long-wavelength gravity waves. Through analyzing the intensity of stratospheric gravity wave disturbances across different latitude bands, we found that in high-latitude regions, stratospheric gravity wave disturbances are most sensitive and respond most quickly to variations in solar activity. Furthermore, the Southern Hemisphere exhibits a stronger response to the current year’s solar activity changes compared to the Northern Hemisphere. In the mid-latitude and equatorial regions, the response to changes in solar activity intensity is delayed. The correlation gradually strengthens with this lag, reaching a very strong level after a 2-year lag. Additionally, the correlation between the Southern Hemisphere and solar activity is generally higher than that of the Northern Hemisphere.

Long term relationships of electron density with solar activity

Greenhouse gases such as carbon dioxide and methane that are causing climate change may cause long term trends in the thermosphere and ionosphere. The paper aims to contribute to explore long term effects in the ionosphere focusing on the impact of solar activity changes. Peak electron density data derived from vertical sounding measurements covering 65 years at the ionosonde stations Juliusruh (JR055), Boulder (BC840) and Kokubunji (TO536), have been utilized to estimate the long-term behavior of daytime ionospheric F2 layer ionization in relation to the solar 10.7 cm radio flux index F10.7. In parallel, Global Navigation Satellite System (GNSS) based vertical total electron content (TEC) data over the ionosonde stations in combination with the peak electron density data have been used to derive the equivalent slab thickness τ for estimating long-term behavior in the time period 1996-2022. A new approach has been developed for deriving production and loss term proxies for studying long-term ionization effects from F2 layer peak electron density and TEC data. The derived coefficients allow estimating the long-term variation of atomic oxygen and molecular nitrogen concentrations including their ratio during winter months. The noon-time slab thickness values over Juliusruh correlate well with the decrease of F10.7 and the F2 layer peak height and enable estimating the neutral gas temperature. The equivalent slab thickness decreases by about 20 km per decade in the period 1996-2022, indicating a thermospheric cooling by about 100 K per decade for Juliusruh. Whereas the oxygen concentration decreases, the loss term, considered as a proxy for molecular components of the neutral gas, in particular N2, increases with the long-term solar activity variation. Considering 11 years averages of the production and loss terms under wintertime conditions, the long-term study reveals for the O/N2 ratio a percentage decrease of 5% per decade and for F10.7 about 3.1% per decade in a linear approach referred to the year 1970. Linear models of 11 years averaged NmF2 and foF2 from corresponding F10.7 show a very close correlation with the temporal variation of F10.7 until about 1990. The root mean square errors are in the order of 1.0 -1.3 ‧1010m-3 for NmF2 and 0.03-0.05 MHz for foF2. After 1990 the linear models clearly deviate from F10.7 at all selected ionosonde stations indicating a non-local effect.

Influence of changes in solar activity on Nigerian Rainfall

This paper focuses on the impact of solar activity changes on rainfall in Nigeria. Rainfall data were got from Gridded Time Series (CRU TS v4) of the University of East Anglia, United Kingdom. Various statistical tools like Pearson rank correlation coefficient, regression analysis, covariance, skewness, and kurtosis are employed in the study. The results show that there are generally weak correlations between rainfall and solar activity in most seasons. However, low correlation coefficients (0.0424 and 0.1040, respectively for sunspot numbers and F10.7 mean a very weak positive relationship between early rainfall, main rainfall and annual rainfall and negative for dry season rainfall and Harmattan rainfall. Also, there is a negative time-series relationship between the rainfall amount in dry and Harmattan seasons, with the highest rainfall amount during low solar activity and vice versa. Therefore, it can be concluded that solar activity has little effect on Nigeria's annual and main season rainfall. However, during the dry season and Harmattan, heavy rainfall appears to be associated with low solar activity, while high solar activity appears to be associated with low rainfall. This study will be beneficial to farmers in Nigeria, majority of whom are peasant farmers that practice rain-fed farming.

About the Possible Solar Nature of the ~200 yr (de Vries/Suess) and ~2000–2500 yr (Hallstadt) Cycles and Their Influences on the Earth’s Climate: The Role of Solar-Triggered Tectonic Processes in General “Sun–Climate” Relationship

(1) Introduction: The subject of the present study concerns the analysis of the existence and long time evolution of the solar ~200 yr (de Vries/Suess) and ~2400 yr (Hallstadt) cycles during the recent part of the Wurm ice epoch and the Holocene, as well as their forcing on the regional East European climate during the last two calendar millennia. The results obtained here are compared with those from our previous studies, as well as with the results obtained by other authors and with other types of data. A possible scenario of solar activity changes during the 21st century, as well as different possible mechanisms of solar–climatic relationships, is discussed. (2) Data and methods: Two types of indirect (historical) data series for solar activity were used: (a) the international radiocarbon tree ring series (INTCAL13) for the last 13,900 years; (b) the Schove series of the calendar years of minima and maxima and the magnitudes of 156 quasi 11 yr sunspot Schwabe–Wolf cycles since 296 AD and up to the sunspot cycle with number 24 (SC24) in the Zurich series; (c) manuscript messages about extreme meteorological and climatic events (Danube and Black Sea near-coast water freezing), extreme summer droughts, etc., in Bulgaria and adjacent territories since 296 and up to 1899 AD, when the Bulgarian meteorological dataset was started. A time series analysis and χ2-test were used. (3) Results and analysis: The amplitude modulation of the 200 yr solar cycle by the 2400 yr (Hallstadt) cycle was confirmed. Two groups of extremely cold winters (ECWs) during the last ~1700 years were established. Both groups without exclusion are concentrated near 11 yr sunspot cycle extremes. The number of ECWs near sunspot cycle minima is about 2 times greater than that of ECWs near sunspot cycle maxima. This result is in agreement with our earlier studies for the instrumental epoch since 1899 AD. The driest “spring-summer-early autumn” seasons in Bulgaria and adjacent territories occur near the initial and middle phases of the grand solar minima of the Oort–Dalton type, which relate to the downward phases and minima of the 200 yr Suess cycle. (4) Discussion: The above results confirm the effect of the Sun’s forcing on climate. However, it cannot be explained by the standard hypothesis for total solar irradiation (TSI) variations. That is why another hypothesis is suggested by the author. The mechanism considered by Svensmark for galactic cosmic ray (GCR) forcing on aerosol nuclei was taken into account. However, in the hypothesis suggested here, the forcing of solar X-ray flux changes (including solar flares) on the low ionosphere (the D-layer) and following interactions with the Earth’s lithosphere due to the terrestrial electric current systems play a key role for aerosol nuclei and cloud generation and dynamics during sunspot maxima epochs. The GCR flux maximum absorption layer at heights of 35–40 km replaces the ionosphere D-layer role during the sunspot minima epochs.

ENSEMBLE MODELS FOR FORECASTING FLOODS IN GREAT BRITAIN BASED ON SOLAR ACTIVITY

This study aims to uncover hidden dependencies between streams of solar particles emanating from the Sun and flood events caused by precipitation in the UK. The uniqueness of this work lies in applying solar activity data as input parameters for machine learning and correlating them with real data on precipitation intensity and floods in the UK, which serve as output data. The analysis covered 20 significant floods from October 2001 to December 2019. The analysis was performed on a daily basis, taking into account the time shift between solar emissions and their impact on terrestrial weather conditions, which ranged from 0 to 9 days. The study employs correlation analysis to determine the degree of interrelation between time series of solar activity and floods, laying the foundation for a deeper understanding of possible cause-and-effect relationships. Subsequently, using predictive modeling methods, including decision tree algorithms and ensemble classification models, the potential connection between changes in solar activity and terrestrial floods was explored. An ensemble of models was created using the hard voting method, which takes into account various indicators such as proton density, differential proton flux, and ion temperature, with a time shift of up to 9 days. The analysis showed that these key parameters could effectively predict the occurrence of floods with up to 92% accuracy for the specified period. The results underscore the importance of integrating space weather and solar activity into the models for predicting terrestrial weather conditions, particularly in the context of floods in England. This not only allows for a better understanding of the causes of natural disasters but also enhances the effectiveness of emergency planning and reduces potential damages from them. Thus, this work makes a significant contribution to the field of space weather research and its impact on Earth, particularly in the areas of hydrometeorology and flood risk management.

Associations between solar and geomagnetic activity and cognitive function in the Normative Aging study

BackgroundStudies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013. MethodsWe used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and Kp index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately. ResultsA one-IQR increase in same-day SSN and Kp index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test. ConclusionsPeriods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted.

Perioperative treatment of Hirschsprung’s disease in children

The aim of this work: to evaluate the eff ectiveness of the developed methods of perioperative treatment of Hirschsprung’s disease in children. Materials and methods. The study was conducted on the basis of the 2nd SamMI clinic in the period from 2002 to 2022. The obtained data were compared by correlation analysis with clinical and laboratory indices and with changes in solar activity by Wolf’s numbers of the period of child embryogenesis, data of Murmansk Department of HMP). Results. The results of the study of the activity of redox enzymes have established the following. When comparing the enzyme spectrum of the affected intestine and intact muscle, only a difference in the activity of SDH and LDH is revealed. Taking into account the activity of all enzymes in relation to the activity of SDH, it can be noted that alternative energy sources have a greater specific weight in the intestinal mucosa than in the muscle.

Long-term temperature trend in the mesopause region according to observations of hydroxyl airglow in Zvenigorod

An analysis of the long-term change of the average annual OH* temperature, the values of which were obtained from nighttime spectral observations of the hydroxyl emission bands at the Zvenigorod scientific station (56° N, 37° E) from 1957 to 2022, is presented. This series of OH* temperatures, reflecting the thermal state of the mesopause region, is the longest among all known observations. On its basis, estimates of the linear trend and response of temperature to changes in solar activity was made both in general over the entire set of data and for different time intervals. In the first case, the trend was −0.23 ± 0.04 K/yr. In the second case, the analysis showed strong cooling (−0.53 ± 0.34 K/yr) until the 1970s and its slowdown to −0.14 ± 0.03 K/yr thereafter. A comparison of the results of the analysis with other measurements and model calculations shows that the latter have lower trend values. It is assumed that the reasons for the temperature trend, in addition to the growth of greenhouse gases, the main of which is CO2, may be long-term changes in the dynamics of the upper atmosphere.

Atmospheric Δ14C in the northern and southern hemispheres over the past two millennia: Role of production rate, southern hemisphere westerly winds and ocean circulation changes

The variations of atmospheric Δ14C over the past two millennia are classically attributed to changes in its production rate in the upper atmosphere, which in turn is related to changes in solar activity and the Earth's magnetic field. However, the potential contribution of atmospheric and oceanic circulation changes during this period has not been precisely quantified. This has been achieved here using a coupled climate model simulating explicitly the evolution of the different carbon isotopes, driven by a new estimate of 14C production derived from 10Be measurements, and using different production rates for each hemisphere. Our results confirm that changes in global and hemispheric atmospheric Δ14C are primarily driven by changes in production rate. The very good agreement between our results and observed atmospheric Δ14C also highlights the strong consistency of current interpretations of 10Be and 14C measurements. By contrast, the interhemispheric difference in atmospheric Δ14C is controlled by changes in the intensity of southern hemisphere westerly winds (SHWW) that impact atmosphere-ocean exchange and the upwelling of 14C depleted water masses in the Southern Ocean. Changes in deep water formation in both hemispheres or open ocean polynyas in the Southern Ocean only have a small impact on atmospheric Δ14C over that period. When driven by changes in the SHWW proportional to three existing reconstructions of the Southern Annular Mode (SAM) index, the model reproduces some key characteristics of the observed interhemispheric Δ14C gradient. These include the low values in the 15th century and the peak in the 16th century, but there are also clear differences between the experiments and Δ14C observations. This suggests that while SAM reconstructions capture some robust features in the centennial variability, large uncertainties remain.

Towards understanding time variations of proton to helium ratios in the heliosphere: Implication for the time dependence of the elements of the diffusion tensor

A comprehensive three-dimensional numerical model for the modulation of cosmic rays in the heliosphere is applied to investigate the relative roles of the time dependence of the elements of the diffusion tensor on the proton to total Helium (p/He) and Helium-3 to Helium-4 (3He2/4He2) ratios at rigidities below 3 GV. At these rigidities the ratios have been observed by both PAMELA and AMS-02 detectors to have a time variation in response to changing solar activity. We found that the contribution of the time dependence of the perpendicular diffusion in the radial direction of the heliosphere is the dominant cause of this observed time variation, especially in the A < 0 magnetic field cycle, and not any fundamental difference between the solar modulation of galactic protons and He-isotopes. It follows that neglecting this time dependence from numerical models, both in value and its rigidity dependence, would produce time trends in the mentioned ratios that are incompatible with observed trends at the Earth. Furthermore, we found differences in the computed time trends of p/He and 3He2/4He2 ratios at rigidities below 1.5 GV. This is mainly a consequence of an interplay between perpendicular diffusion in the radial direction and adiabatic energy losses which begin to influence modulated spectra at a higher rigidity for 3He2 than for 4He2, and for total He than for protons.

Dynamics of dissolved Fe content in tributaries of Lake Teletskoe, depending on solar activity indicators

Relevance. The need to expand and deepen the understanding of the influence of solar radiation indicators on chemical characteristics of surface water, since the dependence of hydrochemical processes on periodic changes in solar activity has so far been studied extremely poorly. In addition, special attention is paid worldwide to the study of iron content in waters of rivers and lakes. Iron increased concentrations are one of the reasons for the "brownification" of surface waters in a significant part of the Northern Hemisphere. Aim. To establish a relationship between iron content and dynamics in the waters of the tributaries of Lake Teletskoe with indicators of solar activity (sunspots number, F-index). Methods. Water samples from the tributaries of Lake Teletskoe were collected into clean new polyethylene bottles in the estuaries of the rivers, from a depth of 0.5 m during the spring-summer high water and autumn low water, in 2016–2020. Content of total and dissolved Fe in the waters was determined by the ISP-MS method and by the AAS method. We used the data on solar activity indicators from the Belgian Observatory, which are freely available. Results. The total Fe content in the rivers of Lake Teletskoe basin for the period from 2016 to 2020 changes from 5 to 340 µg/l. Concentrations of dissolved iron (4 to 200 µg/l) do not exceed Russian standards, but they are often noticeably higher than the global average for river waters established abroad. The highest iron content, as well as the proportion of its soluble forms in the tributaries of Lake Teletskoe and in lake waters, was noted in 2016. It is probably due to the highest rates of solar activity. They cause certain changes in the environment – such as an increase in air temperature and water evaporation, and decrease in river flow, which accompanied by growth in concentrations of chemical elements in surface waters. Since 2016, there has been a steady decrease in dissolved iron concentration in surface natural waters of Lake Teletskoe basin, which may be a consequence of a decrease in solar radiation intensity in recent years.

Characterize the Long-term Ionospheric Response to the Changes in Solar Activity at Low-Latitude Stations of the East African Sector

In this research, we examine the long-term ionospheric response to solar conditions from 2009-2019 using GPS-TEC observations from 8 stations in East Africa at low/equatorial latitudes. To determine the effects of solar activity on ionospheric vertical-Total-Electron-Content (vTEC), solar proxies (EUV, F10.7, and SSN) were used. We have applied statistical analysis and used quadratic fits with solar indices to find the types of trends, forecast vTEC, and describe the daily, monthly, and seasonal variations of vTEC. We stated the fluctuations and dependency of GPS-vTEC on solar activity. From seasonal analysis, the greater values of GPS-vTEC were observed in the equinox’s season from 2009-2016, followed by the December and June solstices, respectively. The highest values of GPS-vTEC were recorded in the years 2014 (70 and 67 TECU), 2013 (57 and 65 TECU), 2012 (56 and 60 TECU) at the March and September equinoxes, and the 2015 March equinox (68 TECU), and the lowest value of GPS-vTEC was recorded (2-3 TECU) for all seasons from 03 to 07 EAT. The changes in vTEC have confirmed worthy agreement with the changes in solar parameters, and EUV flux has a stronger association with vTEC than the F10.7 and SSN by 2% and 7%, respectively. Daily and monthly variations of vTEC showed positive associations with the solar parameters (EUV, F10.7, and SSN) from 2009-2019. We got both linear and nonlinear trends; however, when we approximated (EUV)2,(F10.7)2, and (SSN)2 coefficients, linear trends in vTEC were dominant. This analysis confirms that a quadratic polynomial can well capture the long-term solar activity dependency of vTEC in a statistical sense; based on the anticipated and observed vTEC values, the modeled outcome is suitable using EUV, F10.7, and SSN indices. But the modeled result is better using EUV and F10.7 than SSN in the region. In the predictions of vTEC, the maximum deviations and number of errors were observed during solar maxima years for EUV, F10.7, and SSN compared with the deviations and number of errors in solar minima years. Therefore, F10.7 is a better proxy of EUV flux in solar cycle 24 using monthly values, and the EUV flux is a better controller of GPS-vTEC changes compared to F10.7 and SSN, even if F10.7 is a proxy of EUV based on daily values.

Long-term changes in solar activity and irradiance

The Sun is the main energy source to Earth, and understanding its variability is of direct relevance to climate studies. Measurements of total solar irradiance (TSI) exist since 1978, but this is too short compared to climate-relevant time scales. Coming from a number of different instruments, these measurements require a cross-calibration, which is not straightforward, and thus several composite records have been created. All of them suggest a marginally decreasing secular trend in solar minima levels since 1996. Most composites actually feature a weak decrease over the entire period of observations, which is also seen in observations of the solar surface magnetic field and is further supported by Caii Kdata. Some inconsistencies, however, remain and overall the magnitude and even the presence of the secular change over the satellite era remain uncertain. Different models have been developed, which are used to understand the irradiance variability over the satellite period and to extend the records of solar irradiance back in time. Differing in their methodologies, all models require proxies of solar magnetic activity as input. The most widely used proxies are sunspot records and cosmogenic isotope data on centennial and millennial time scale, respectively. None of this, however, offers a sufficiently good, independent description of the long-term evolution of faculae and network responsible for solar brightening. This leads to significant uncertainties in the amplitude of the changes in solar irradiance on time scales longer than the solar cycle. Here we review recent efforts and advances aiming at improving long-term irradiance reconstructions and to reduce the existing uncertainty in the magnitude of the long-term variability. In particular, by employing state-of-the-art 3D magnetohydrodynamical simulations, an upper limit of 2±0.7 Wm−2 was set on the possible increase of TSI since the end of the Maunder minimum as compared to the 2019 minimum level. Besides, significant progress has been made in collecting and processing historical solar observation in Caii Kspectral line, which provide direct information on bright magnetic features on the Sun and can be used to improve the accuracy of past irradiance reconstructions, pending some remaining issues with the data.

Analysis of the electromagnetic availability of radio signal sources during propagation in the ionosphere radio channel

Problem statement. Multi-channel automated short-wave radio communication networks are used to provide information support for the activities of critical facilities and the organization of information exchange between subscribers assigned to a large area, as well as the control of aircraft when flying at transcontinental ranges and sea vessels in remote areas of the world ocean. The probabilistic-temporal characteristics of the effectiveness of monitoring their dynamic states largely depend on the electromagnetic availability of radiation sources. The conditions of their electromagnetic availability must be determined by the values of the maximum applicable frequency and spatial-energy characteristics of the signals in the ionosphere radio channel. Time periods of stable reception must be set taking into account possible changes in ray trajectories and fading (fading) of signals due to refraction in ionized layers of the atmosphere during daily and seasonal fluctuations of electrical parameters. To determine the current values of the radio channel parameters, the International Reference Model of the Ionosphere and GOST 25645.146-89 “Earth's Ionosphere. Model of the global distribution of concentration, temperature and effective frequency of electron collisions”, which reflects the patterns of distribution of average values of the electron concentration in the Earth's ionosphere at different times of the year and day with changes in solar and geomagnetic activity. Goal. Evaluation of the electromagnetic availability of short wave emitters for monitoring posts based on a rational choice of operating frequencies and finding the spatial and energy characteristics of signal reception. Results. A predictive model has been developed for assessing the electromagnetic accessibility of radio signal sources by the values of the maximum applicable frequency and spatial and energy characteristics during propagation in the ionosphere radio channel. The profile of the ionized layers of the atmosphere and the structure of radio channel undergo changes depending on the mutual position of the Earth and the Sun, as well as solar activity and the latitude of the observation site. In the profile of the ionized structure of the atmosphere, four characteristic regions are conventionally distinguished – layers D, E, F1, F2. Due to the intrinsic fluctuations in the parameters of ionized layers under the influence of a large number of factors, ground-based complexes of vertical (inclined) sounding and a satellite system for observing the ionosphere do not provide the required reliability of data on its state in real time for the entire surface of the Earth. Based on certain values of the optimal operating frequencies and inclination angles of the ionosphere wave ray trajectories, the time intervals of the electromagnetic availability of transmitters located in different regions in the summer and autumn-winter periods were found. Based on the estimates of the maximum applicable signal frequencies in the ionosphere radio channel using an azimuth-elevation detector-direction finder located in the Central Federal District, the angles of inclination of the trajectories when receiving radio station signals meteorology information of airfield networks of the Russian Federation and neighboring countries were determined. The detector-direction finder used an active antenna array of 16 asymmetric vibrators 2.5 m high, located on an area of 200×200 m, and synchronized coherent radio devices with frequency conversion. Measurements were carried out in the Doppler ray separation mode when selecting signals at matching frequencies was carried out in accordance with the time schedule for the operation of radio stations. On routes with a length of about 1000 km, variations in the directions of arrival of signals along the elevation angle with 3 reflections from the ionosphere reach 15...20°, and in the azimuth plane - up to 4...5°. On routes with a length of more than 1000 km, the fading of signals is determined by the interference of beams commensurate in level; on routes with a length of more than 2000 km, as a rule, one beam prevails, and fading is due to a change in its heterogeneous-style in time. Practical significance. The predictive model for analyzing the electromagnetic availability of radio emission sources makes it possible to select the modes of operation of monitoring posts with the establishment of a period of time with the best conditions for receiving signals in given areas, based on the values of the maximum applicable frequency of radio channels and the angles of arrival of a sky wave with the highest power. The obtained results form the basis for improving the technology of monitoring the radio-electronic situation when receiving signals propagating over the ionosphere radio channel, and justifying the tactical and technical requirements for the characteristics of high frequency range direction finders.

CASHEW, A RESPONSE TO THE COCOA CRISIS IN DIMBOKRO IN THE N'ZI REGION? (IVORY COAST)

As the Sun progresses through its solar cycle and its activity increases, a greater number of sunspots occur, and solar fluxes become more intense. The change in solar activity is related to the change in electron and ion density of the ionosphere. Studying this relation is very important in terms of space plasma studies and space weather predictions, which play a significant role in radio and satellite communication as well as GPS navigation. In this paper, we are presenting the sunspot and solar flux data for solar cycle 24 (year 2008-2020). We are using C/NOFS satellite data to understand the variationof ion densities of the upper atmosphere with solar cycle 24. Our analysis shows decrease of H+ density by a factor of 10 and increase of O+ density by a factor of 10 during solar maxima. This data set can be used as a framework for future advancement in empirical modelling of regional and global ion density of the ionosphere.

New insights into potential effects of solar activity on the oxygen isotope composition of modern speleothems: Observations from Jiguan Cave, central China II

The oxygen isotope compositions (δ18O) of stalagmites have been widely used to reconstruct summer monsoon variability, which is primarily controlled by the solar radiation on orbital to seasonal timescales. However, the relationship between solar activity and the monsoon system remains unclear. This study is based on a 13-year, from 2010 to 2022, monitoring campaign of the δ18O values of precipitation, cave drips and modern speleothems in Jiguan Cave, central China. By analyzing moisture circulation and the local meteoric water line (LMWL) under different ENSO (El Niño Southern Oscillation) events, it was found that on seasonal–interannual timescales, the precipitation δ18O values reflect the atmospheric moisture circulation. In addition, we used cross-wavelet transform analysis to investigate the periodic relationship between the sunspot number (SSN) and the Asian Summer Monsoon (ASM) since solar activity is one of the most important external influences on the ASM. The stalagmite δ18O data for our study areas reflect the solar activity-induced decadal-scale variations in the local precipitation. The key factors related to the δ18O value include the driving mechanism of the solar activity and ENSO-related sea surface temperature (SST) anomalies. We speculate that changes in solar activity cause anomalies in the tropical SST gradient, which affects central China's hydrological cycle by changing the variability of ENSO and the Indian Ocean Dipole (IOD) and ultimately causes the variations in stalagmites δ18O records.

SOLAR ACTIVITY VARIATION AND ITS EFFECTS ON IONOSPHERIC ION DENSITIES

As the Sun progresses through its solar cycle and its activity increases, a greater number of sunspots occur, and solar fluxes become more intense. The change in solar activity is related to the change in electron and ion density of the ionosphere. Studying this relation is very important in terms of space plasma studies and space weather predictions, which play a significant role in radio and satellite communication as well as GPS navigation. In this paper, we are presenting the sunspot and solar flux data for solar cycle 24 (year 2008-2020). We are using C/NOFS satellite data to understand the variationof ion densities of the upper atmosphere with solar cycle 24. Our analysis shows decrease of H+ density by a factor of 10 and increase of O+ density by a factor of 10 during solar maxima. This data set can be used as a framework for future advancement in empirical modelling of regional and global ion density of the ionosphere.