Journal of Atmospheric and Solar-Terrestrial Physics最新文献

{"title":"Propagation of whistler-mode waves transmitted by the DSX satellite","authors":"Anatoly V. Streltsov ,&nbsp;Jay M. Albert ,&nbsp;Michael J. Starks","doi":"10.1016/j.jastp.2025.106530","DOIUrl":"10.1016/j.jastp.2025.106530","url":null,"abstract":"<div><div>Experiments consisting of the transmission and receiving of ELF (300-3000 Hz) whistler-mode waves were conducted on board of DSX satellite. In several events, the transmitted waves were received by the same antenna on the satellite after a time delay of several hundred milliseconds. These events suggest that the transmitted waves propagate mostly along the ambient magnetic field, reflect at some location along their path, and return back to the satellite. The main questions related to these observations are: (1) What causes the guiding of the waves along the ambient magnetic field? and (2) Where in the magnetosphere are these waves reflected? The results from analytical and numerical studies presented in this paper indicate that the waves are guided by the field-aligned density inhomogeneities (aka ducts), and they are reflected from the ends of the duct.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"272 ","pages":"Article 106530"},"PeriodicalIF":1.8,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144070337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of geomagnetic storm-induced energetic particle precipitations in the modification of the ionosphere over the American and African longitudinal sectors","authors":"B.A. Ojapinwa,&nbsp;E.O. Oyeyemi,&nbsp;A.O. Akala","doi":"10.1016/j.jastp.2025.106539","DOIUrl":"10.1016/j.jastp.2025.106539","url":null,"abstract":"<div><div>Geomagnetic storms are associated with changes in electron and proton fluxes in the radiation belts, leading to precipitation. However, most past studies have been done based on storms’ intensities. This study investigates the roles of eight geomagnetic storms, classified by their intensities using Dst threshold conditions, and interplanetary drivers, in the production of Energetic Particle Precipitation (EPP), and their subsequent modification of ionospheric irregularities and Total Electron Content (TEC). We used energetic particle fluxes, TEC, interplanetary magnetic field, and solar wind data. The rate of TEC index (ROTI) was used as a proxy for ionospheric irregularities. In this study, the ability of a storm to induce EPPs is predominant and significant during the recovery phases of storms. Consequently, the modifications of the ionosphere caused by EPPs were mostly pronounced during the recovery phase of a storm. At the recovery phases, enhanced EPPs induced by intense sheath (SH)- and Corotating Interaction Region (CIR)-driven storms caused corresponding enhancements in TEC and ionospheric irregularities, while that of intense magnetic cloud (MC)-driven storm showed no significant effect on TEC and irregularities. Furthermore, enhanced EPP induced by intense and moderate MC + SH-driven storms caused little or no change in TEC and ionospheric irregularities. In addition, an enhanced EPP induced by moderate sheath- and MC-driven storms caused depletion in TEC and irregularities. Irregularities were more prevalent at the low- and high-latitude, but less in occurrences at the mid-latitude in the African sector. Overall, from this study, the African sector responded more to the energetic particles than the American sector. Irregularities at the high-latitude stations were generally high and frequent regardless of the phase, magnitude, driver, or local times of occurrence of storms. The storm-induced EPP enhancements were more significant in the southern hemisphere than in the northern hemisphere, and the events of the equinoctial months showed more dependence on EPPs.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"273 ","pages":"Article 106539"},"PeriodicalIF":1.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144083609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The importance of electric field or/and neutral wind in formation and prediction of sporadic E (Es) at the equatorial and mid-latitude regions","authors":"Goderdzi G. Didebulidze ,&nbsp;Giorgi Dalakishvili ,&nbsp;Maya Todua ,&nbsp;Lekso Toriashvili","doi":"10.1016/j.jastp.2025.106540","DOIUrl":"10.1016/j.jastp.2025.106540","url":null,"abstract":"<div><div>This study investigates the formation and localization of sporadic E(Es) at equatorial and mid-latitude regions in case of presence of electric field or/and neutral wind. It has been shown that at the equatorial region, in analogy to the mid-latitude regions, the necessary condition for development of ion vertical convergence and formation of sporadic E (Es) is the presence of the minimal negative value of ion drift velocity divergence in its height profile (including only a vertical component). This condition at the equatorial region is significantly determined by the neutral wind velocity and the zonal and vertical components of the electric field, even when this field is homogeneous. The ions vertical convergence developed in these regions and the formation of the Es layer can take place against the background of their upward or downward drift. Sporadic layer localizes either at the node of the ions drift velocity, or in the regions where this velocity disappears. The formation and dynamics of Es layers are demonstrated by numerical methods which makes possible its prediction. The effects of the zonal and vertical components of the electric field, as well as the wind velocity (determined by the HWM14 data), on the processes of ion convergence/divergence development, at equatorial and mid-latitudes, are shown. In these cases, the ion convergence/divergence, induced by the electric field, can affect both the formation and disruption (depletion) of the Es layer formed by neutral wind, and can also increase its density or/and form an additional layer. It is also shown that the presence of electric field, along with the meridional and zonal wind at mid-latitudes, can affect both the formation and the behavior of Es layers at these regions.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"272 ","pages":"Article 106540"},"PeriodicalIF":1.8,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144070338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of X-ray radiation from a solar flare on the frequencies of Schumann resonances","authors":"V.V. Surkov","doi":"10.1016/j.jastp.2025.106537","DOIUrl":"10.1016/j.jastp.2025.106537","url":null,"abstract":"<div><div>In this paper, a theoretical model of the effect of X-ray radiation from a solar flare on the Earth's ionosphere and on the Schumann resonance frequencies in the Earth-ionosphere waveguide has been constructed. A flat transient flux of X-ray photons incident on the Earth is considered. By making the assumption that the absorption coefficient of photon energy depends on their energy and air density, the air ionization rate under the action of X-ray radiation is found as a function of altitude. Changes in the number densities of electrons and ions are described by a set of differential equations, which take into account the rate of production and recombination of particles, as well as the attachment of electrons to neutral molecules. The altitude profiles of all reaction constants, as well as the mobility of electrons and ions, are approximated using tabular data. The solution of these equations is used to calculate changes in ionospheric conductivity caused by X-rays from a solar flare. A case study of X6.9-class solar flare effect on the ionosphere is being studied, although the variability of model parameters could affect the simulation results. The changes in conductivity influence on the penetration depth of the low-frequency electromagnetic field into the conducting ionosphere, which results in a slight increase in the frequencies of the Schumann resonances. The theory explains the relationship between the intensity of X-ray radiation and the change in the weighted average frequency of Schumann resonances, which was observed for a number of solar flares of various classes.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106537"},"PeriodicalIF":1.8,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of laser beam propagation through atmospheric turbulence and its impact on CCD sensor intensity distribution","authors":"Maryam Jafari,&nbsp;Masoud Mollaee,&nbsp;Khashayar Heshmati Jannat Magham,&nbsp;Mahmoud Rezaee Rokanabadi","doi":"10.1016/j.jastp.2025.106527","DOIUrl":"10.1016/j.jastp.2025.106527","url":null,"abstract":"<div><div>This study investigates the propagation of laser beams with Gaussian and Laguerre-Gaussian profiles through atmospheric turbulence and their subsequent detection by charge-coupled device (CCD) sensors. Using numerical simulations based on the Kolmogorov turbulence model, we analyze the intensity distribution of laser beams under turbulence strengths ranging from 10⁻¹⁶ to 10⁻¹² and propagation distances of 500 m to 5 km. The effects of atmospheric turbulence on photon distribution at the CCD sensor's pixels are quantified, revealing beam broadening with Full Width at Half Maximum (FWHM) increasing from 50 μm to 1.5 m under the highest turbulence conditions. Saturation and blooming phenomena are observed, with photon density exceeding 10⁶ photons/pixel in high-intensity regions. Our findings reveal that turbulence-induced distortions significantly impact beam intensity profiles, with higher turbulence levels causing up to a 70 % reduction in central intensity. Additionally, the study highlights the sensitivity of higher-order Laguerre-Gaussian modes, which exhibit up to 90 % greater broadening compared to fundamental Gaussian modes. By evaluating the impact of aperture size and f-number on beam focusing, we show that increasing the f-number from 2 to 8 reduces saturation artifacts by 60 % while spreading intensity over a larger area.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106527"},"PeriodicalIF":1.8,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the recent biennial variability of the lower stratospheric water vapor","authors":"Reetambhara Dutta,&nbsp;S. Sridharan","doi":"10.1016/j.jastp.2025.106535","DOIUrl":"10.1016/j.jastp.2025.106535","url":null,"abstract":"<div><div>The Microwave Limb Sounder (MLS)-Aura water vapor mixing ratio (WVMR) exhibits a clear biennial variability in the lower stratosphere (∼82 hPa) with larger values during October of alternate years 2015, 2017, 2019, 2021 and 2023. The temperature at 100 hPa and ozone mixing ratio at 82 hPa exhibit similar large values in July–August. Unlike earlier years, a phase transition of quasi-biennial oscillation (QBO) in winds (70 hPa) is observed at the beginning of the years. The corresponding warm QBO temperature anomalies descend to even 125 hPa in July–August to cause increased water vapor injection through the warmer tropopause.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106535"},"PeriodicalIF":1.8,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143928310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of machine learning models to estimate particulate matter (2.5) in oil producing Arab countries: Kuwait as a case study","authors":"Sharaf AlKheder,&nbsp;Hajar Al-Otaibi","doi":"10.1016/j.jastp.2025.106536","DOIUrl":"10.1016/j.jastp.2025.106536","url":null,"abstract":"<div><div>Air pollution is one of the most serious environmental issues facing the State of Kuwait. The environment and the population's health depend on the state's ability to maintain air quality. Most air pollution is caused by the increasing population, increased human activities, and increased vehicle ownership. Reducing pollution and preserving the environment therefore depends on managing environmental pollutants. This research aimed to create a reliable method for assessing the concentrations of Particulate Matter 2.5 (PM_2.5; i.e., particles with a diameter less than 2.5 μm (μm)), one of the most harmful pollutants. Most of the existing studies on air quality prediction in Kuwait or similar areas face some challenges in the model accuracy, lack of datasets, and environmental variation. To address these challenges, four machine learning models: neural network models, support vector machine algorithms, generalized additive models, and random forests were used. The models were trained in four scenarios: daily or monthly data and data divided by city or aggregated. The results showed that the random forest model outperformed the others in predicting PM_2.5 concentration in all scenarios, with Coefficient of determination (<em>R</em>²) over 0.85, root mean squared error (RMSE) under 6.25 μg/m³ and mean absolute error (MAE) under 6.17 μg/m³. This study can be used as a guide for choosing the best model for estimating daily PM_2.5 concentrations in Kuwait and other places with the same climate.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106536"},"PeriodicalIF":1.8,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143898804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of meteorological variability on aerosol size distribution during the winter fog campaign over Delhi: a case study","authors":"A.K. Srivastava ,&nbsp;K. Ram ,&nbsp;D.S. Bisht ,&nbsp;M.P. Raju ,&nbsp;V. Singh ,&nbsp;V.K. Soni","doi":"10.1016/j.jastp.2025.106531","DOIUrl":"10.1016/j.jastp.2025.106531","url":null,"abstract":"<div><div>The aerosol size distribution, particularly the number and mass distributions, plays a crucial role in understanding changes in optical properties due to hygroscopic growth, which affects visibility and radiative forcing on a regional scale. The Indo-Gangetic Plain (IGP), including National Capital Region (NCR) of Delhi, experiences severe fog and haze with reduced visibility during the post-monsoon to winter months (October–February) every year. This study reports aerosol mass size distribution over Delhi during a winter fog campaign (December 15, 2015–February 15, 2016) using a ground-based optical particle counter. The fine and coarse mode aerosols were contributed to ∼85% and 15% to the total aerosol mass concentration during the campaign period. The characteristic changes in aerosol size distribution, effective radius, and the influence of meteorological factors, particularly relative humidity (RH) and temperature, under three visibility conditions: Vis-1 (&lt;600 m), Vis-2 (600–1200 m), and Vis-3 (&gt;1200 m) were investigated. Fine-mode aerosols accounted for ∼85 % of the total aerosol mass, with their concentration increasing by a factor of 3.7 during Vis-1 and 2.3 during Vis-2 compared to Vis-3, when the effective radius of aerosol was lowest (R_eff: 0.44 μm). Fine particle concentrations showed a positive correlation with RH (R = 0.35) and a negative correlation with visibility (R = −0.65), suggesting that the high RH and fine-mode aerosols contribute to fog formation and reduced visibility in Delhi-NCR.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106531"},"PeriodicalIF":1.8,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine learning based method for dynamic forecasting of total electron content in the equatorial ionosphere","authors":"Sumitra Iyer ,&nbsp;Yogesh Jadhav ,&nbsp;Harsh Taneja ,&nbsp;Daivik Padmanabhan","doi":"10.1016/j.jastp.2025.106533","DOIUrl":"10.1016/j.jastp.2025.106533","url":null,"abstract":"<div><div>The total electron content in the ionosphere is a vital parameter for the users of the Global Navigation Satellite System (GNSS) as it causes a delay in the satellite signal propagating through it, which in turn degrades the positional accuracy of the receiver. Thus, improving the GNSS positioning requires precise ionospheric Total Electron Content (TEC) prediction, especially in the equatorial region where complex electrodynamics and erratic space weather events introduce substantial short-term variability. Although deep learning techniques have shown promise, they frequently rely heavily on large historical datasets, are computationally demanding, and are not interpretable. In this work, we propose a Multiclass Classifier Short-Term Dynamic Prediction Model (MSTDM) that uses reliable and interpretable machine learning techniques to forecast Vertical TEC (VTEC) 30 min ahead of time. The model optimizes the training set using a threshold-based learning algorithm to identify nonrepetitive and relevant VTEC patterns from recent data. The model uses polynomial interpolation to impute missing values, and a sliding window method is used to extract temporal features, which are then further refined through statistical feature selection. The continuous VTEC values are first discretized into distinct classes, after which Support Vector Machines (SVM) and Random Forests (RF) were employed for supervised classification. Different feature selection techniques were used. Prediction accuracy for SVM and RF with Recursive Feature Elimination (RFE) demonstrated the best results during geomagnetic storm days. The results varied from 85 to 91 % and 87–92 %, respectively. The RF-RFE model outperformed other configurations with 99 % training accuracy and 96 % test accuracy. Thus, this method provided a high-performing, interpretable, and computationally efficient solution for short-term VTEC forecasting.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"271 ","pages":"Article 106533"},"PeriodicalIF":1.8,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143922432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conjugate hemisphere asymmetric variation in sporadic E: Role of wind shear and meteor ions","authors":"Bitap Raj Kalita ,&nbsp;P.K. Bhuyan ,&nbsp;Kehe Wang","doi":"10.1016/j.jastp.2025.106532","DOIUrl":"10.1016/j.jastp.2025.106532","url":null,"abstract":"<div><div>The long-term (7 years) ionosonde observations of sporadic E (foEs) at two magnetically conjugate stations in the 95°E longitude, and the HWM vertical wind profiles are utilized to investigate the role of meteor ion deposition rates and vertical wind shear in the seasonal variation of Es. The chosen geometry of the two stations is such that southern station (Cocos islands,12.2°S, 96°N, geo-mag lat:21°S) is geographically at the low latitude, whereas the northern station (Dibrugarh 27.5°N, 95°E, geo-mag lat: 18°N) is at the <em>low</em> mid-latitude due to the north-shifted dip equator. The statistical observations show nearly invariant seasonal characteristics of Es at the southern low-latitude station (during low solar activity)in contrast to the summer maximum at the <em>low</em> mid-latitude station. Both low and high intensity Es over Cocos were found to be anti-correlated with solar activity. However, the high-intensity Es (&gt;7 MHz) at the southern station is more frequent in the solstice. During the high solar activity period, the seasonal invariance is not maintained, and the minimum is recorded during the March equinox. The local time variation of foEs occurrence shows diurnal (semi-diurnal) oscillation at low (mid) latitude station. The HWM vertical profile of zonal winds show that wind shear depth at the low latitude station has low seasonal variation, whereas, at the <em>low</em> middle latitude station the maximum wind shear peaks during summer. Analysis of previously reported radar observations shows that the season of minimum (maximum) meteor deposition rate at equatorial/low-latitude (middle-latitude) regions are aligned with the observed season of minimum (maximum) of Es at low (middle) latitudes. Therefore, the difference of the seasonal variation of sporadic E (Es) at the two conjugate stations may be explained by a combined mechanism of wind shear variation and meteor deposition rates.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"272 ","pages":"Article 106532"},"PeriodicalIF":1.8,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143947338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}