Pub Date : 2025-10-21DOI: 10.1016/j.jastp.2025.106661
D. Sierra-Porta
Galactic cosmic rays (GCR) modulate atmospheric ionisation and may influence reactive greenhouse gases, yet linear correlations have proved inconclusive. We analyse 74 328 hourly observations (2016–2024) of pressure-corrected neutron-monitor counts and co-located CH and O mixing ratios from the high-alpine Jungfraujoch station using Multifractal Detrended Fluctuation Analysis (MFDFA) and its bivariate extension (MFDCCA). Cosmic rays exhibit a narrow, quasi-monofractal singularity spectrum (), consistent with heliospheric modulation as a single dominant driver, whereas O and CH display progressively broader spectra ( and 0.84). Cross-Hurst exponents exceed unity for small-to-moderate fluctuations, indicating super-persistent joint variability on 1–7 d (O) and 7–30 d (CH) horizons—time-scales compatible with HO/NO chemistry triggered by GCR ionisation. Quadratic fits to the cross-singularity spectra yield half-maximum widths of 0.39 (CH–GCR) and (O–GCR), quantifying a broader amplitude hierarchy for methane. Extreme gas anomalies, by contrast, show weak cross persistence, implicating dynamical intrusions rather than ionisation. Multifractal metrics thus expose a scale-selective GCR imprint masked in Pearson and Spearman statistics and suggest that incorporating GCR flux as a multiscale covariate could improve sub-monthly O/CH predictions. The approach provides a transferable framework for disentangling cosmic-ray forcing from chemical and dynamical controls in other trace-gas records.
银河宇宙射线（GCR）调节大气电离并可能影响活性温室气体，但线性相关性已被证明是不确定的。利用多重分形去趋势波动分析（MFDFA）及其二元扩展（MFDCCA）方法，对2016-2024年高高山少女峰站压力校正中子监测计数和同地CH4和O3混合比的74328 h观测数据进行了分析。宇宙射线表现出狭窄的准单分形奇异光谱（Δαfull=0.43），与日球层调制作为单一主导驱动因素相一致，而O3和CH4则显示出逐渐扩大的光谱（Δα=0.78和0.84）。Cross-Hurst指数在小到中等波动中超过一，表明在1-7 d （O3）和7-30 d （CH4）水平时间尺度上的超持久联合变异与GCR电离引发的HOx/NOx化学反应相容。交叉奇异谱的二次拟合得到半最大宽度为0.39 （CH4-GCR）和0.33 (O3-GCR)，量化了甲烷更广泛的振幅层次。相比之下，极端气体异常表现出微弱的交叉持久性，暗示动力学侵入而不是电离。因此，多重分形指标揭示了皮尔逊和斯皮尔曼统计数据中掩盖的尺度选择性GCR印记，并表明将GCR通量作为多尺度协变量可以改善亚月O3/CH4预测。该方法为将宇宙射线强迫与其他痕量气体记录中的化学和动力学控制分离开来提供了一个可转移的框架。
{"title":"Scale-dependent coupling between galactic cosmic rays and trace gases revealed by multifractal analysis","authors":"D. Sierra-Porta","doi":"10.1016/j.jastp.2025.106661","DOIUrl":"10.1016/j.jastp.2025.106661","url":null,"abstract":"<div><div>Galactic cosmic rays (GCR) modulate atmospheric ionisation and may influence reactive greenhouse gases, yet linear correlations have proved inconclusive. We analyse 74<!--> <!-->328 hourly observations (2016–2024) of pressure-corrected neutron-monitor counts and co-located CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> and O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> mixing ratios from the high-alpine Jungfraujoch station using Multifractal Detrended Fluctuation Analysis (MFDFA) and its bivariate extension (MFDCCA). Cosmic rays exhibit a narrow, quasi-monofractal singularity spectrum (<span><math><mrow><mi>Δ</mi><msub><mrow><mi>α</mi></mrow><mrow><mtext>full</mtext></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>43</mn></mrow></math></span>), consistent with heliospheric modulation as a single dominant driver, whereas O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> and CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> display progressively broader spectra (<span><math><mrow><mi>Δ</mi><mi>α</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>78</mn></mrow></math></span> and 0.84). Cross-Hurst exponents exceed unity for small-to-moderate fluctuations, indicating super-persistent joint variability on 1–7 d (O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>) and 7–30 d (CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>) horizons—time-scales compatible with HO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span>/NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> chemistry triggered by GCR ionisation. Quadratic fits to the cross-singularity spectra yield half-maximum widths of 0.39 (CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>–GCR) and <span><math><mrow><mo><</mo><mn>0</mn><mo>.</mo><mn>33</mn></mrow></math></span> (O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>–GCR), quantifying a broader amplitude hierarchy for methane. Extreme gas anomalies, by contrast, show weak cross persistence, implicating dynamical intrusions rather than ionisation. Multifractal metrics thus expose a scale-selective GCR imprint masked in Pearson and Spearman statistics and suggest that incorporating GCR flux as a multiscale covariate could improve sub-monthly O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>/CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> predictions. The approach provides a transferable framework for disentangling cosmic-ray forcing from chemical and dynamical controls in other trace-gas records.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106661"},"PeriodicalIF":1.9,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145359170","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}
Pub Date : 2025-10-19DOI: 10.1016/j.jastp.2025.106665
Xinming Zhang , M.V. Subrahmanyam , Zhou Le , Dongxiao Wang
Previous studies have conducted a comprehensive examination of the impact of wind speed on monsoon precipitation; however, the significance of wind direction remains largely unexplored. This analysis utilizes ERA-5 reanalysis data to quantitatively investigate the directional characteristics of the Arabian Sea low-level jet (LLJ) over the last four decades. It applies wind angle metrics to evaluate the LLJ's direction and its influence on monsoon precipitation over the Western Ghats (WG), with a larger angle signifying that the LLJ is more aligned with the southerly wind. At 925 hPa, the LLJ exhibits a greater wind angle than at 850 hPa, showing an upward trend. This finding suggests a northerly movement of the LLJ, potentially associated with the Pacific Decadal Oscillation. Statistical analysis reveals that a larger LLJ angle is associated with heightened precipitation on the northern windward slopes of the WG, and precipitation decreases in the southern regions, suggesting the influence of the LLJ's directional changes on precipitation patterns. The results offer valuable perspectives for enhancing monsoon predictions and deepening our scientific comprehension of the relationship between the LLJ and precipitation.
{"title":"Directional characteristics of low-level jet over the Arabian Sea and its impact on monsoon precipitation over the Western Ghats","authors":"Xinming Zhang , M.V. Subrahmanyam , Zhou Le , Dongxiao Wang","doi":"10.1016/j.jastp.2025.106665","DOIUrl":"10.1016/j.jastp.2025.106665","url":null,"abstract":"<div><div>Previous studies have conducted a comprehensive examination of the impact of wind speed on monsoon precipitation; however, the significance of wind direction remains largely unexplored. This analysis utilizes ERA-5 reanalysis data to quantitatively investigate the directional characteristics of the Arabian Sea low-level jet (LLJ) over the last four decades. It applies wind angle metrics to evaluate the LLJ's direction and its influence on monsoon precipitation over the Western Ghats (WG), with a larger angle signifying that the LLJ is more aligned with the southerly wind. At 925 hPa, the LLJ exhibits a greater wind angle than at 850 hPa, showing an upward trend. This finding suggests a northerly movement of the LLJ, potentially associated with the Pacific Decadal Oscillation. Statistical analysis reveals that a larger LLJ angle is associated with heightened precipitation on the northern windward slopes of the WG, and precipitation decreases in the southern regions, suggesting the influence of the LLJ's directional changes on precipitation patterns. The results offer valuable perspectives for enhancing monsoon predictions and deepening our scientific comprehension of the relationship between the LLJ and precipitation.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106665"},"PeriodicalIF":1.9,"publicationDate":"2025-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145359095","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}
Pub Date : 2025-10-17DOI: 10.1016/j.jastp.2025.106653
K. Mursula
Sunspots offer a uniquely long view of solar magnetic activity, and depict large variability during the last 100 years, a period known as the Modern Maximum (MM). However, if our view of solar variability was only based on the strongest magnetic fields, it would be incomplete. Therefore, other variables are needed to study the long-term evolution, e.g., of weaker magnetic fields and the different radiative emissions. Recently, the relation between sunspots and several other solar activity proxies like the F10.7 and F30 radio fluxes and the MgII index (all proxies of EUV irradiance) was found to vary during the last 70 years so that a relative sunspot dominance over EUV in the 1950s–1960s changed to EUV dominance in the 2000s (Mursula et al., 2024). Here we use data from eight long-operating observatories to calculate the yearly range of daily variation of the geomagnetic Y-component, the rY index, for the last 137 years. We show that the rY index correlates extremely well with the MgII index and the solar F30 radio flux. These three indices have no trend relative to each other over the respective intervals. On the other hand, the F10.7 flux has a significant trend with respect to the three co-varying EUV indices (MgII, F30, rY). Therefore, the rY index replaces F10.7 as the best long-term EUV proxy, and extends the MgII index by 90 years. We verify that all the four EUV proxies (rY, MgII, F30, F10.7) have an increasing trend with respect to sunspots during the last 50–70 years. This is valid both for sunspot numbers and group numbers. Extending this earlier with the rY index, we find that the relation between EUV irradiance and sunspots has a nonlinear, quadratic evolution over the MM. This implies that the Sun has more sunspots relative to EUV irradiance during the growth and maximum of the MM, while the opposite is true during its decay and minimum. We estimate that the MgII index (solar EUV irradiance) increases by 24% of its solar cycle variation with respect to the sunspot number during the last 70 years. Our results indicate a systematic difference in the evolution between sunspots (generally: photosphere) and plages (generally: chromosphere) with long-term solar activity. The implied varying spot-facula ratio has consequences to the stellar evolution of the Sun and Sun-like stars.
太阳黑子提供了一个独特的太阳磁活动的长期视图，并描绘了过去100年的大变化，这一时期被称为现代极大期（MM）。然而，如果我们对太阳变化的看法仅仅基于最强的磁场，那将是不完整的。因此，需要其他变量来研究长期演变，例如，较弱的磁场和不同的辐射发射。最近，太阳黑子与其他几个太阳活动指标(如F10.7和F30射电通量以及MgII指数（所有EUV辐照度的指标）之间的关系在过去70年中发生了变化，因此，20世纪50年代至60年代太阳黑子对EUV的相对优势转变为21世纪初的EUV优势（Mursula et al., 2024）。在这里，我们使用八个长期运行的观测站的数据来计算过去137年来地磁y分量（y指数）的日变化的年范围。我们发现rY指数与MgII指数和太阳F30射电通量的相关性非常好。这三个指数在各自的区间内没有相互的趋势。另一方面，F10.7通量相对于三个共变EUV指数（MgII、F30、rY）有显著的变化趋势。因此，rY指数取代F10.7成为最佳的长期EUV指标，并将MgII指数延长90年。我们验证了在过去50-70年间，所有四个EUV代理（rY, MgII, F30, F10.7）在太阳黑子方面都有增加的趋势。这对太阳黑子数和群数都是有效的。用rY指数扩展这一点，我们发现EUV辐照度和太阳黑子之间的关系在MM上具有非线性的二次演化。这意味着在MM的增长和最大值期间，太阳相对于EUV辐照度有更多的太阳黑子，而在其衰减和最小值期间则相反。我们估计，在过去70年中，MgII指数（太阳EUV辐照度）相对于太阳黑子数的太阳周期变化增加了24%。我们的研究结果表明，太阳黑子（通常是光球层）和太阳黑子（通常是色球层）在长期太阳活动中的演化存在系统差异。暗变的斑光斑比对太阳和类太阳恒星的演化有影响。
{"title":"Centennial solar EUV irradiance from ionospheric currents: Varying sunspot-EUV irradiance relation and modified spot-facula ratio","authors":"K. Mursula","doi":"10.1016/j.jastp.2025.106653","DOIUrl":"10.1016/j.jastp.2025.106653","url":null,"abstract":"<div><div>Sunspots offer a uniquely long view of solar magnetic activity, and depict large variability during the last 100 years, a period known as the Modern Maximum (MM). However, if our view of solar variability was only based on the strongest magnetic fields, it would be incomplete. Therefore, other variables are needed to study the long-term evolution, e.g., of weaker magnetic fields and the different radiative emissions. Recently, the relation between sunspots and several other solar activity proxies like the F10.7 and F30 radio fluxes and the MgII index (all proxies of EUV irradiance) was found to vary during the last 70 years so that a relative sunspot dominance over EUV in the 1950s–1960s changed to EUV dominance in the 2000s (Mursula et al., 2024). Here we use data from eight long-operating observatories to calculate the yearly range of daily variation of the geomagnetic Y-component, the rY index, for the last 137 years. We show that the rY index correlates extremely well with the MgII index and the solar F30 radio flux. These three indices have no trend relative to each other over the respective intervals. On the other hand, the F10.7 flux has a significant trend with respect to the three co-varying EUV indices (MgII, F30, rY). Therefore, the rY index replaces F10.7 as the best long-term EUV proxy, and extends the MgII index by 90 years. We verify that all the four EUV proxies (rY, MgII, F30, F10.7) have an increasing trend with respect to sunspots during the last 50–70 years. This is valid both for sunspot numbers and group numbers. Extending this earlier with the rY index, we find that the relation between EUV irradiance and sunspots has a nonlinear, quadratic evolution over the MM. This implies that the Sun has more sunspots relative to EUV irradiance during the growth and maximum of the MM, while the opposite is true during its decay and minimum. We estimate that the MgII index (solar EUV irradiance) increases by 24% of its solar cycle variation with respect to the sunspot number during the last 70 years. Our results indicate a systematic difference in the evolution between sunspots (generally: photosphere) and plages (generally: chromosphere) with long-term solar activity. The implied varying spot-facula ratio has consequences to the stellar evolution of the Sun and Sun-like stars.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106653"},"PeriodicalIF":1.9,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145359171","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}
Pub Date : 2025-10-17DOI: 10.1016/j.jastp.2025.106663
M. Kasiselvanathan, P. Sridevi
Rapid population enhancement and economic development have significantly changed land use and land cover (LULC) in ecologically sensitive Sundarbans, the world's most fragile ecosystem. Accurate classification of LULC is important for environmental monitoring, resource management, and policy-making. In the present paper, the authors have employed a machine learning (ML) technique, Random Forest (RF), to classify land cover changes in the Sundarbans over two time periods: 2003, and 2023. Landsat-7 and Landsat-8 satellite imagery have been used for land cover (LC) analysis, followed by data pre-processing techniques including layer stacking, mosaicking, and spectral signature collection. Around 640 and 840 training samples have been used for classification, for the year 2003 and 2023 respectively with 30 % samples used for validation. The RF model utilized 500 trees (n-tree) and four variables at each split (m-try). The accuracy has been assessed with confusion matrices, and Kappa statistics showing an accuracy of 0.84 and 0.85 for the year 2003 and 2023 respectively. The result reveals an increase in sparse forest, open land, and sand bar, and decline in water bodies and dense forest. The reason may be due to anthropogenic activities and climate-induced factors such as rising sea levels and storm surges. The findings indicate Sundarbans ecosystem's susceptibility and the necessity of sustainable management techniques. This study indicates that future research should focus on longer time-series analysis, improved scalability, and cloud platform integration to improve. The research demonstrates that ML-based land cover classification can be a useful monitoring tool with high accuracy for environmental conservation.
{"title":"Supervised land cover classification of the Indian Sundarbans mangrove forest using random forest and Landsat imagery","authors":"M. Kasiselvanathan, P. Sridevi","doi":"10.1016/j.jastp.2025.106663","DOIUrl":"10.1016/j.jastp.2025.106663","url":null,"abstract":"<div><div>Rapid population enhancement and economic development have significantly changed land use and land cover (LULC) in ecologically sensitive Sundarbans, the world's most fragile ecosystem. Accurate classification of LULC is important for environmental monitoring, resource management, and policy-making. In the present paper, the authors have employed a machine learning (ML) technique, Random Forest (RF), to classify land cover changes in the Sundarbans over two time periods: 2003, and 2023. Landsat-7 and Landsat-8 satellite imagery have been used for land cover (LC) analysis, followed by data pre-processing techniques including layer stacking, mosaicking, and spectral signature collection. Around 640 and 840 training samples have been used for classification, for the year 2003 and 2023 respectively with 30 % samples used for validation. The RF model utilized 500 trees (n-tree) and four variables at each split (m-try). The accuracy has been assessed with confusion matrices, and Kappa statistics showing an accuracy of 0.84 and 0.85 for the year 2003 and 2023 respectively. The result reveals an increase in sparse forest, open land, and sand bar, and decline in water bodies and dense forest. The reason may be due to anthropogenic activities and climate-induced factors such as rising sea levels and storm surges. The findings indicate Sundarbans ecosystem's susceptibility and the necessity of sustainable management techniques. This study indicates that future research should focus on longer time-series analysis, improved scalability, and cloud platform integration to improve. The research demonstrates that ML-based land cover classification can be a useful monitoring tool with high accuracy for environmental conservation.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106663"},"PeriodicalIF":1.9,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324936","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}
Pub Date : 2025-10-17DOI: 10.1016/j.jastp.2025.106664
Yunxiao Chen, Jinfu Liu, Daren Yu
With the increasing penetration rate of wind and solar energy, the difference between load demand and renewable energy has gradually become the main regulating object (net load) of the power system. The daily net load curve is called the duck curve due to its shape. Duck curves pose new requirements for the overall flexibility of power system resources in terms of power output and power ramp. In order to reduce the cost and difficulty of balancing the duck curve in the power system, this paper proposes a method for constructing a friendly duck curve. Firstly, a friendliness evaluation framework consisting of 8 indicators is proposed to assess the quality of the duck curve. Secondly, through short-term optimization, long-term optimization and real-time adjustment for the wind-solar energy capacity layout of 26 grids in Belgium, the friendly duck curves are achieved. Meanwhile, four conventional wind-solar energy layouts are used as comparison groups. Finally, as the typical representative of flexibility resources, thermal power units are used to measure the net load and difficulty and cost of climbing the balance duck curves. The results indicate that the friendly duck curve requires a smaller scale of flexibility resources compared to conventional duck curves.
{"title":"Wind meets solar: crafting the perfect duck curve for future power systems","authors":"Yunxiao Chen, Jinfu Liu, Daren Yu","doi":"10.1016/j.jastp.2025.106664","DOIUrl":"10.1016/j.jastp.2025.106664","url":null,"abstract":"<div><div>With the increasing penetration rate of wind and solar energy, the difference between load demand and renewable energy has gradually become the main regulating object (net load) of the power system. The daily net load curve is called the duck curve due to its shape. Duck curves pose new requirements for the overall flexibility of power system resources in terms of power output and power ramp. In order to reduce the cost and difficulty of balancing the duck curve in the power system, this paper proposes a method for constructing a friendly duck curve. Firstly, a friendliness evaluation framework consisting of 8 indicators is proposed to assess the quality of the duck curve. Secondly, through short-term optimization, long-term optimization and real-time adjustment for the wind-solar energy capacity layout of 26 grids in Belgium, the friendly duck curves are achieved. Meanwhile, four conventional wind-solar energy layouts are used as comparison groups. Finally, as the typical representative of flexibility resources, thermal power units are used to measure the net load and difficulty and cost of climbing the balance duck curves. The results indicate that the friendly duck curve requires a smaller scale of flexibility resources compared to conventional duck curves.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106664"},"PeriodicalIF":1.9,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145359096","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}
Pub Date : 2025-10-17DOI: 10.1016/j.jastp.2025.106662
Sevim Yasemin Oturanc
With recent advances in satellite technologies, remote sensing techniques have become more frequently used in monitoring water surfaces. The Catalan Reservoir, located on the Seyhan River, is an important source of drinking water, agricultural irrigation, and electricity generation for the city of Adana in southern Türkiye. Therefore, continuous monitoring of the water surface is necessary. In this study, Sentinel-2B MSI images dated December 24, 2023 were used to determine the reservoir water surface area using three spectral indices: Normalized Difference Water Index (NDWI), Water Ratio Index (WRI), and Modified Normalized Difference Water Index (MNDWI), and two supervised pixel-based classification techniques: Support Vector Machines (SVM) and Artificial Neural Networks (ANN). The reservoir water surface area was determined to be 69.3 km2 with 98.6 % accuracy using NDWI, 67.7 km2 with 98.3 % accuracy using WRI, and 69.9 km2 with 97.6 % accuracy using MNDWI. Supervised classifications provided 68.3 km2 with 98.6 % accuracy for SVM and 66.7 km2 with 99 % accuracy for ANN. These findings demonstrate that spectral indices perform similarly to classification methods and can be used as practical alternatives. The novelty of this study is that the highest-accuracy ANN pixel-based classification algorithm is used for the first time in conjunction with WRI. This integration provides more accurate results for remote sensing of water resources.
{"title":"Performance analysis of machine learning techniques and spectral indices of determination water surface areas using Sentinel-2B satellite imagery","authors":"Sevim Yasemin Oturanc","doi":"10.1016/j.jastp.2025.106662","DOIUrl":"10.1016/j.jastp.2025.106662","url":null,"abstract":"<div><div>With recent advances in satellite technologies, remote sensing techniques have become more frequently used in monitoring water surfaces. The Catalan Reservoir, located on the Seyhan River, is an important source of drinking water, agricultural irrigation, and electricity generation for the city of Adana in southern Türkiye. Therefore, continuous monitoring of the water surface is necessary. In this study, Sentinel-2B MSI images dated December 24, 2023 were used to determine the reservoir water surface area using three spectral indices: Normalized Difference Water Index (NDWI), Water Ratio Index (WRI), and Modified Normalized Difference Water Index (MNDWI), and two supervised pixel-based classification techniques: Support Vector Machines (SVM) and Artificial Neural Networks (ANN). The reservoir water surface area was determined to be 69.3 km<sup>2</sup> with 98.6 % accuracy using NDWI, 67.7 km<sup>2</sup> with 98.3 % accuracy using WRI, and 69.9 km<sup>2</sup> with 97.6 % accuracy using MNDWI. Supervised classifications provided 68.3 km<sup>2</sup> with 98.6 % accuracy for SVM and 66.7 km<sup>2</sup> with 99 % accuracy for ANN. These findings demonstrate that spectral indices perform similarly to classification methods and can be used as practical alternatives. The novelty of this study is that the highest-accuracy ANN pixel-based classification algorithm is used for the first time in conjunction with WRI. This integration provides more accurate results for remote sensing of water resources.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106662"},"PeriodicalIF":1.9,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145359230","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}
A project for a multi-satellite constellation designed to monitor space radiation is being developed at Moscow State University. A number of small CubeSat satellites have been launched into selected orbits crossing a wide range of magnetic drift shells. The main objective of the project is to promptly monitor the radiation situation in near-Earth space — fluxes of charged particles (mainly electrons) of the Earth's radiation belts and energetic particles of solar and galactic origin. Today, there are 7 MSU CubeSat satellites operating in near-Earth orbits, transmitting scientific and telemetry data. Thus, for the first time, a unique multi-satellite constellation has been implemented that allows simultaneous measurement of particle and photon fluxes in various regions of near-Earth space using identical devices. Special compact detectors of gamma rays and energetic charged particles (primarily electrons) DeCoR have been developed for radiation monitoring using CubeSat. They are used to observe various effects of space weather. These effects include the filling of polar caps with solar energetic particles (SEP) accelerated in solar flares - solar cosmic ray (SCR) events. The SCR events of October 2024, observed after powerful solar flares, were chosen as an example.
{"title":"Observations of solar cosmic ray events and hard X-ray during strong solar flares in October 2024 on Moscow University nanosatellite Avion","authors":"A.V. Bogomolov , V.V. Bogomolov , A.F. Iyudin , V.V. Kalegaev , I.N. Myagkova , V.I. Osedlo , S.I. Svertilov , I.V. Yashin","doi":"10.1016/j.jastp.2025.106656","DOIUrl":"10.1016/j.jastp.2025.106656","url":null,"abstract":"<div><div>A project for a multi-satellite constellation designed to monitor space radiation is being developed at Moscow State University. A number of small CubeSat satellites have been launched into selected orbits crossing a wide range of magnetic drift shells. The main objective of the project is to promptly monitor the radiation situation in near-Earth space — fluxes of charged particles (mainly electrons) of the Earth's radiation belts and energetic particles of solar and galactic origin. Today, there are 7 MSU CubeSat satellites operating in near-Earth orbits, transmitting scientific and telemetry data. Thus, for the first time, a unique multi-satellite constellation has been implemented that allows simultaneous measurement of particle and photon fluxes in various regions of near-Earth space using identical devices. Special compact detectors of gamma rays and energetic charged particles (primarily electrons) DeCoR have been developed for radiation monitoring using CubeSat. They are used to observe various effects of space weather. These effects include the filling of polar caps with solar energetic particles (SEP) accelerated in solar flares - solar cosmic ray (SCR) events. The SCR events of October 2024, observed after powerful solar flares, were chosen as an example.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106656"},"PeriodicalIF":1.9,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324938","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}
Pub Date : 2025-10-10DOI: 10.1016/j.jastp.2025.106659
Yongliang Zhang, Jesper W. Gjerloev, Larry J. Paxton, Robert Schaefer, Matt Friel
We introduce a new criterion: A ground state of the geospace (the magnetosphere, ionsophere and thermosphere) where all of three regions are undisturbed by the impact of the solar wind particle, energy, and momentum inputs. It is challenging to find such days when the impact is minimized and the geospace is at its ground state (super quiet) or undisturbed condition. After a search of databases of SuperMAG SME index and DMSP SSUSI aurora data over two decades (2002–2022), we identified a few rare super quiet intervals using two criteria: (1) A very low geomagnetic activity (AE or SME <50 nT, SmH >0 nT), and (2) a very weak auroral activity with auroral oval above 70° magnetic latitude and N2 Lyman-Birge-Hopfield Short (LBHS, 140–150 nm) auroral intensity below 500 R, over 48 consecutive hours or longer. Here we report one super quiet interval (November 6–7, 2009). This interval occurred during the deep solar minimum with daily F10.7 around 70. The low auroral intensity (particle precipitation) and coincident weak plasma convection indicates low ionospheric density and Joule/particle heating at high latitudes. This super quiet condition leads to an undisturbed thermosphere: without any O/N2 depletion or nitric oxide (NO) enhancement at high latitudes. The super quiet interval was driven by a long (∼61 h), steady and weak solar wind (velocity ∼300 km/s, dynamic pressure 1–2 nPa) and a northward IMF (Interplanetary Magnetic Field) Bz (0–4 nT). These solar wind driving conditions lead to a near zero solar wind-magnetosphere coupling rate and to what we refer as a “geospace ground state”.
{"title":"A ground state of the geospace on November 6–7, 2009","authors":"Yongliang Zhang, Jesper W. Gjerloev, Larry J. Paxton, Robert Schaefer, Matt Friel","doi":"10.1016/j.jastp.2025.106659","DOIUrl":"10.1016/j.jastp.2025.106659","url":null,"abstract":"<div><div>We introduce a new criterion: A ground state of the geospace (the magnetosphere, ionsophere and thermosphere) where all of three regions are undisturbed by the impact of the solar wind particle, energy, and momentum inputs. It is challenging to find such days when the impact is minimized and the geospace is at its ground state (super quiet) or undisturbed condition. After a search of databases of SuperMAG SME index and DMSP SSUSI aurora data over two decades (2002–2022), we identified a few rare super quiet intervals using two criteria: (1) A very low geomagnetic activity (AE or SME <50 nT, SmH >0 nT), and (2) a very weak auroral activity with auroral oval above 70° magnetic latitude and N<sub>2</sub> Lyman-Birge-Hopfield Short (LBHS, 140–150 nm) auroral intensity below 500 R, over 48 consecutive hours or longer. Here we report one super quiet interval (November 6–7, 2009). This interval occurred during the deep solar minimum with daily F10.7 around 70. The low auroral intensity (particle precipitation) and coincident weak plasma convection indicates low ionospheric density and Joule/particle heating at high latitudes. This super quiet condition leads to an undisturbed thermosphere: without any O/N<sub>2</sub> depletion or nitric oxide (NO) enhancement at high latitudes. The super quiet interval was driven by a long (∼61 h), steady and weak solar wind (velocity ∼300 km/s, dynamic pressure 1–2 nPa) and a northward IMF (Interplanetary Magnetic Field) B<sub>z</sub> (0–4 nT). These solar wind driving conditions lead to a near zero solar wind-magnetosphere coupling rate and to what we refer as a “geospace ground state”.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106659"},"PeriodicalIF":1.9,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324939","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}
Pub Date : 2025-10-10DOI: 10.1016/j.jastp.2025.106658
A.A. Karakhanyan, S.I. Molodykh
Meteorological records show an increase in the intensity and frequency of hazardous weather phenomena on the planet. Solar activity is one of the climate-forming factors and, along with carbon dioxide, can influence the Earth's climate. The indirect mechanism of solar activity influence on the climate system is discussed. The ionospheric electric potential (EP), caused by changes in the solar wind and interplanetary magnetic field, plays an important role in this mechanism. Our investigation studies the possibility of using EP as an indicator of solar activity to analyze the outgoing longwave radiation (OLR) response during an individual powerful geomagnetic disturbance, such as the May 11, 2024 geomagnetic superstorm. The EP contrast averaged for the latitudes region above 60° N correlates well with high-, mid-, and low-latitude geomagnetic indices. Unlike geomagnetic indices, the spatial distribution of the EP enables us to analyze the spatial structure of OLR's response to disturbances. Changes in EP have been shown to lead to a decrease in OLR. However, the contribution of meteorological variability on time scales of less than one month must be considered for individual powerful magnetic storms. The EP can therefore be used as new indicator of solar activity to solve the solar-tropospheric problem.
{"title":"The influence of the ionospheric electric potential on outgoing longwave radiation in the troposphere during the May 11, 2024 geomagnetic superstorm","authors":"A.A. Karakhanyan, S.I. Molodykh","doi":"10.1016/j.jastp.2025.106658","DOIUrl":"10.1016/j.jastp.2025.106658","url":null,"abstract":"<div><div>Meteorological records show an increase in the intensity and frequency of hazardous weather phenomena on the planet. Solar activity is one of the climate-forming factors and, along with carbon dioxide, can influence the Earth's climate. The indirect mechanism of solar activity influence on the climate system is discussed. The ionospheric electric potential (EP), caused by changes in the solar wind and interplanetary magnetic field, plays an important role in this mechanism. Our investigation studies the possibility of using EP as an indicator of solar activity to analyze the outgoing longwave radiation (OLR) response during an individual powerful geomagnetic disturbance, such as the May 11, 2024 geomagnetic superstorm. The EP contrast averaged for the latitudes region above 60° N correlates well with high-, mid-, and low-latitude geomagnetic indices. Unlike geomagnetic indices, the spatial distribution of the EP enables us to analyze the spatial structure of OLR's response to disturbances. Changes in EP have been shown to lead to a decrease in OLR. However, the contribution of meteorological variability on time scales of less than one month must be considered for individual powerful magnetic storms. The EP can therefore be used as new indicator of solar activity to solve the solar-tropospheric problem.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106658"},"PeriodicalIF":1.9,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324923","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}
Pub Date : 2025-10-10DOI: 10.1016/j.jastp.2025.106657
P.G. Richards , J.T. Emmert
This study examines how well the ionosphere peak electron density can be simulated with the Field Line Interhemispheric Plasma (FLIP) model given the current knowledge of chemistry, solar EUV radiation, and thermosphere densities. The simulations were conducted at many mid-latitude ionosonde stations over a wide range of solar activity conditions to compare the different model results from the new NRLMSIS 2.0 thermosphere model (Emmert et al., 2020) with the older NRLMSISE-00 model (Picone et al., 2002). These FLIP model-data results may help isolate times and places for needed improvement to the thermosphere models. The NRLMSISE-00 version of the FLIP model (FLIP0) yields daytime peak F-region electron density (NmF2) agreement well within the measurement and model errors at most stations in the Southern Hemisphere. In the Northern Hemisphere, there is good model-data agreement around the June solstice but significant differences in the American and European sectors. The NRLMSIS 2.0 version (FLIP2) produces slightly lower NmF2 values overall than FLIP0, but it causes a significant overestimation in the Australian sector at the March equinox for high solar activity. Neither the FLIP0 nor FLIP2 model adequately captures the changes in NmF2 due to enhanced magnetic activity, especially the greater variability near the equinoxes, that has been attributed to the orientation of the Earth's rotation axis with the solar wind. The data show that magnetic activity is more important than solar activity for determining changes in NmF2 over a solar rotation period.
本研究考察了在现有的化学知识、太阳EUV辐射和热层密度的情况下，用场线半球间等离子体（FLIP）模型模拟电离层峰值电子密度的效果。模拟在许多中纬度电离层监测站进行，在广泛的太阳活动条件下进行，以比较新的NRLMSIS 2.0热层模式（Emmert et al., 2020）与旧的NRLMSIS -00模式（Picone et al., 2002）的不同模式结果。这些FLIP模式数据结果可能有助于隔离时间和地点，以便对热层模式进行必要的改进。NRLMSISE-00版本的FLIP模型（FLIP0）产生的白天峰值f区电子密度（NmF2）在南半球大多数站点的测量和模型误差范围内很好地吻合。在北半球，在6月至日前后有很好的模型数据一致性，但在美国和欧洲部门有显著差异。NRLMSIS 2.0版本（FLIP2）产生的NmF2值总体上略低于FLIP0，但它在3月春分太阳活动高的澳大利亚部门造成了显著的高估。FLIP0和FLIP2模型都没有充分捕捉到NmF2由于磁场活动增强而产生的变化，特别是在春分点附近的更大变化，这归因于地球自转轴与太阳风的方向。数据表明，在确定太阳自转周期内NmF2的变化时，磁活动比太阳活动更重要。
{"title":"How accurately can the ionosphere peak electron density be modeled?","authors":"P.G. Richards , J.T. Emmert","doi":"10.1016/j.jastp.2025.106657","DOIUrl":"10.1016/j.jastp.2025.106657","url":null,"abstract":"<div><div>This study examines how well the ionosphere peak electron density can be simulated with the Field Line Interhemispheric Plasma (FLIP) model given the current knowledge of chemistry, solar EUV radiation, and thermosphere densities. The simulations were conducted at many mid-latitude ionosonde stations over a wide range of solar activity conditions to compare the different model results from the new NRLMSIS 2.0 thermosphere model (Emmert et al., 2020) with the older NRLMSISE-00 model (Picone et al., 2002). These FLIP model-data results may help isolate times and places for needed improvement to the thermosphere models. The NRLMSISE-00 version of the FLIP model (FLIP0) yields daytime peak F-region electron density (<em>N</em><sub><em>m</em></sub><em>F</em><sub>2</sub>) agreement well within the measurement and model errors at most stations in the Southern Hemisphere. In the Northern Hemisphere, there is good model-data agreement around the June solstice but significant differences in the American and European sectors. The NRLMSIS 2.0 version (FLIP2) produces slightly lower <em>N</em><sub><em>m</em></sub><em>F</em><sub>2</sub> values overall than FLIP0, but it causes a significant overestimation in the Australian sector at the March equinox for high solar activity. Neither the FLIP0 nor FLIP2 model adequately captures the changes in <em>N</em><sub><em>m</em></sub><em>F</em><sub>2</sub> due to enhanced magnetic activity, especially the greater variability near the equinoxes, that has been attributed to the orientation of the Earth's rotation axis with the solar wind. The data show that magnetic activity is more important than solar activity for determining changes in <em>N</em><sub><em>m</em></sub><em>F</em><sub>2</sub> over a solar rotation period.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"277 ","pages":"Article 106657"},"PeriodicalIF":1.9,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324934","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}
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