Pub Date : 2024-01-09DOI: 10.3389/fspas.2023.1284913
E. Johnson, B. A. Maruca, M. McManus, M. Stevens, K. G. Klein, P. Mostafavi
Collisional analysis combines the effects of collisional relaxation and large-scale expansion to quantify how solar wind parameters evolve as the plasma expands through the heliosphere. Though previous studies have applied collisional analysis to the temperature ratio between protons (ionized hydrogen) and α-particles (fully ionized helium), this is the first study to explore α-proton differential flow with collisional analysis. First, the mathematical model for the collisional analysis of differential flow was derived. Then, this model was applied to individual in-situ observations from Parker Solar Probe (PSP; r = 0.1–0.27 au) to generate predictions of the α-proton differential flow in the near-Earth solar wind. A comparison of these predicted values with contemporaneous measurements from the Wind spacecraft (r = 1.0 au) shows strong agreement, which may imply that the effects of expansion and Coulomb collisions have a large role in governing the evolution of differential flow through the inner heliosphere.
{"title":"Application of collisional analysis to the differential velocity of solar wind ions","authors":"E. Johnson, B. A. Maruca, M. McManus, M. Stevens, K. G. Klein, P. Mostafavi","doi":"10.3389/fspas.2023.1284913","DOIUrl":"https://doi.org/10.3389/fspas.2023.1284913","url":null,"abstract":"Collisional analysis combines the effects of collisional relaxation and large-scale expansion to quantify how solar wind parameters evolve as the plasma expands through the heliosphere. Though previous studies have applied collisional analysis to the temperature ratio between protons (ionized hydrogen) and α-particles (fully ionized helium), this is the first study to explore α-proton differential flow with collisional analysis. First, the mathematical model for the collisional analysis of differential flow was derived. Then, this model was applied to individual in-situ observations from Parker Solar Probe (PSP; r = 0.1–0.27 au) to generate predictions of the α-proton differential flow in the near-Earth solar wind. A comparison of these predicted values with contemporaneous measurements from the Wind spacecraft (r = 1.0 au) shows strong agreement, which may imply that the effects of expansion and Coulomb collisions have a large role in governing the evolution of differential flow through the inner heliosphere.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"17 22","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139443512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-08DOI: 10.3389/fspas.2023.1298609
Keahi Pelkum Donahue, Fadil Inceoglu
Space weather phenomena, including solar flares and coronal mass ejections, have significant influence on Earth. These events can cause satellite orbital decay due to heat-induced atmospheric expansion, disruption of GPS navigation and telecommunications systems, damage to satellites, and widespread power blackouts. The potential of flares and associated events to damage technology and disrupt human activities motivates prediction development. We use Transformer networks to predict whether an active region (AR) will release a flare of a specific class within the next 24 h. Two cases are considered: ≥C-class and ≥M-class. For each prediction case, separate models are developed. We train the Transformer to use time-series data to classify 24- or 48-h sequences of data. The sequences consist of 18 physical parameters that characterize an AR from the Space-weather HMI Active Region Patches data product. Flare event information is obtained from the Geostationary Operational Environmental Satellite flare catalog. Our model outperforms a prior study that similarly used only 24 h of data for the ≥C-class case and performs slightly worse for the ≥M-class case. When compared to studies that used a larger time window or additional data such as flare history, results are comparable. Using less data is conducive to platforms with limited storage, on which we plan to eventually deploy this algorithm.
{"title":"Forecasting solar flares with a transformer network","authors":"Keahi Pelkum Donahue, Fadil Inceoglu","doi":"10.3389/fspas.2023.1298609","DOIUrl":"https://doi.org/10.3389/fspas.2023.1298609","url":null,"abstract":"Space weather phenomena, including solar flares and coronal mass ejections, have significant influence on Earth. These events can cause satellite orbital decay due to heat-induced atmospheric expansion, disruption of GPS navigation and telecommunications systems, damage to satellites, and widespread power blackouts. The potential of flares and associated events to damage technology and disrupt human activities motivates prediction development. We use Transformer networks to predict whether an active region (AR) will release a flare of a specific class within the next 24 h. Two cases are considered: ≥C-class and ≥M-class. For each prediction case, separate models are developed. We train the Transformer to use time-series data to classify 24- or 48-h sequences of data. The sequences consist of 18 physical parameters that characterize an AR from the Space-weather HMI Active Region Patches data product. Flare event information is obtained from the Geostationary Operational Environmental Satellite flare catalog. Our model outperforms a prior study that similarly used only 24 h of data for the ≥C-class case and performs slightly worse for the ≥M-class case. When compared to studies that used a larger time window or additional data such as flare history, results are comparable. Using less data is conducive to platforms with limited storage, on which we plan to eventually deploy this algorithm.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"1 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-08DOI: 10.3389/fspas.2023.1329284
Honghong Wu, Liping Yang, Shiyong Huang
The highly Alfvénic fluctuations (AF) and magnetic-velocity alignment structures (MVAS) are two distinguished components in the near-Sun slow solar wind observed by Parker Solar Probe. The amplitudes of the Elsässer Variables z± of AF and MVAS show distinct features. However, how these fluctuations contribute to the slow solar wind turbulence remains unknown. Here we investigate the coherence between z+ and z− for the first time using the Parker Solar Probe measurements with a high resolution 0.8738 s in the slow solar wind from 0.1–0.3 au. We find that the coherence spectra of z+ and z− in the perpendicular directions for MVAS are remarkable higher than that for AF, in particular at large scale. There exists a break around 10 di (di is the ion inertial length) where the coherence decreases to a lower level for MVAS. A bump around 10 di appears on the coherence spectra of all three components for AF. The coherence of z+ and z− may relate to the possible nonlinear interactions reflected by the time series, the power spectra, and the self-correlation functions. These results help to understand the roles of AF and MVAS in the slow solar wind turbulence.
帕克太阳探测器（Parker Solar Probe）观测到的近太阳慢速太阳风中，高度阿尔费尼波动（AF）和磁速度排列结构（MVAS）是两个不同的组成部分。AF和MVAS的埃尔塞变量z±的振幅显示出明显的特征。然而，这些波动如何导致慢太阳风湍流仍是未知数。在这里，我们首次利用帕克太阳探测器在 0.1-0.3 au 的慢太阳风中进行的 0.8738 s 高分辨率测量，研究了 z+ 和 z- 之间的相干性。我们发现，MVAS 的 z+ 和 z- 在垂直方向上的相干谱明显高于 AF，尤其是在大尺度上。在 10 di（di 为离子惯性长度）附近存在一个断点，MVAS 的相干性在此断点下降到较低水平。对于 AF，所有三个分量的相干光谱在 10 di 附近都出现了一个凸起。z+ 和 z- 的一致性可能与时间序列、功率谱和自相关函数所反映的可能的非线性相互作用有关。这些结果有助于理解 AF 和 MVAS 在慢太阳风湍流中的作用。
{"title":"Coherence of Elsässer Variables in the slow solar wind from 0.1 au to 0.3 au","authors":"Honghong Wu, Liping Yang, Shiyong Huang","doi":"10.3389/fspas.2023.1329284","DOIUrl":"https://doi.org/10.3389/fspas.2023.1329284","url":null,"abstract":"The highly Alfvénic fluctuations (AF) and magnetic-velocity alignment structures (MVAS) are two distinguished components in the near-Sun slow solar wind observed by Parker Solar Probe. The amplitudes of the Elsässer Variables z± of AF and MVAS show distinct features. However, how these fluctuations contribute to the slow solar wind turbulence remains unknown. Here we investigate the coherence between z+ and z− for the first time using the Parker Solar Probe measurements with a high resolution 0.8738 s in the slow solar wind from 0.1–0.3 au. We find that the coherence spectra of z+ and z− in the perpendicular directions for MVAS are remarkable higher than that for AF, in particular at large scale. There exists a break around 10 di (di is the ion inertial length) where the coherence decreases to a lower level for MVAS. A bump around 10 di appears on the coherence spectra of all three components for AF. The coherence of z+ and z− may relate to the possible nonlinear interactions reflected by the time series, the power spectra, and the self-correlation functions. These results help to understand the roles of AF and MVAS in the slow solar wind turbulence.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"13 2","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-08DOI: 10.3389/fspas.2023.1328364
Garrett Zills, Serena Criscuoli, L. Bertello, Alexei Pevtsov
Studies of stellar magnetic fields mostly rely on proxies derived from chromospheric lines, typically forming in the UV and shorter wavelengths and therefore accessible only from space based observatories. Even Ca II K or H observations, forming in regions accessible from the ground, are not always available. As a result, there is a crucial need to explore alternative activity proxies to overcome the limitations posed by observational constraints. Using sun-as-a-star observations acquired with the ISS at SOLIS we investigated the correlation between the Ca II K emission index and indices derived from the Hα 656.3 nm and Ca II 854.2 nm lines, which are well known chromospheric diagnostics. We found that both the core intensities and widths of the two lines are positively correlated with the Ca II K emission index (ρ ≳ 0.8), indicating their suitability as reliable indicators of magnetic activity, the width of the Hα line showing the highest correlation (ρ = 0.9). We also found that such correlations vary with the activity cycle. Specifically, during the analyzed cycle 24, the correlations with the Ca II K index varied 14% for the Hα width, 33% for the Hα core intensity, and doubled for the two Ca II 854.2 nm line indices. These results suggest that, among the investigated indices, the Hα width best traces magnetic activity. Results are discussed at the light of current knowledge of the formation heights of the two lines, and of spatially resolved solar observations.
对恒星磁场的研究大多依赖于色球层线得出的近似值，这些线通常形成于紫外线和较短波长，因此只能从空间观测站获得。即使是在地面可以观测到的区域内形成的 Ca II K 或 H 观测数据，也并非总能获得。因此，亟需探索替代活动代用指标，以克服观测制约带来的限制。利用国际空间站在 SOLIS 上获取的太阳-恒星观测数据，我们研究了 Ca II K 发射指数与 Hα 656.3 nm 和 Ca II 854.2 nm 线得出的指数之间的相关性。我们发现这两条线的核心强度和宽度都与 Ca II K 发射指数呈正相关（ρ ≳0.8），表明它们适合作为磁活动的可靠指标，其中 Hα 线的宽度显示出最高的相关性（ρ = 0.9）。我们还发现，这种相关性随活动周期而变化。具体来说，在分析的周期 24 中，Hα 宽度与 Ca II K 指数的相关性变化了 14%，Hα 核心强度变化了 33%，而两个 Ca II 854.2 nm 线指数的相关性变化了一倍。这些结果表明，在所研究的指数中，Hα 宽度最能追踪磁活动。根据目前对这两条线形成高度的了解，以及对太阳空间分辨观测的了解，对结果进行了讨论。
{"title":"Sun-as-a-star variability of Hα and Ca II 854.2 nm lines","authors":"Garrett Zills, Serena Criscuoli, L. Bertello, Alexei Pevtsov","doi":"10.3389/fspas.2023.1328364","DOIUrl":"https://doi.org/10.3389/fspas.2023.1328364","url":null,"abstract":"Studies of stellar magnetic fields mostly rely on proxies derived from chromospheric lines, typically forming in the UV and shorter wavelengths and therefore accessible only from space based observatories. Even Ca II K or H observations, forming in regions accessible from the ground, are not always available. As a result, there is a crucial need to explore alternative activity proxies to overcome the limitations posed by observational constraints. Using sun-as-a-star observations acquired with the ISS at SOLIS we investigated the correlation between the Ca II K emission index and indices derived from the Hα 656.3 nm and Ca II 854.2 nm lines, which are well known chromospheric diagnostics. We found that both the core intensities and widths of the two lines are positively correlated with the Ca II K emission index (ρ ≳ 0.8), indicating their suitability as reliable indicators of magnetic activity, the width of the Hα line showing the highest correlation (ρ = 0.9). We also found that such correlations vary with the activity cycle. Specifically, during the analyzed cycle 24, the correlations with the Ca II K index varied 14% for the Hα width, 33% for the Hα core intensity, and doubled for the two Ca II 854.2 nm line indices. These results suggest that, among the investigated indices, the Hα width best traces magnetic activity. Results are discussed at the light of current knowledge of the formation heights of the two lines, and of spatially resolved solar observations.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"6 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139445357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-05DOI: 10.3389/fspas.2023.1338284
Fengjie Li, Jiansen Du, Shang Wang, Ruitao Yu, Xi Wang, Tiqiang Zhang, Zongtao Chi, Bin Wang, Ning Li
Infrared observation is a crucial tool in the study of astronomical celestial bodies. Metamaterials have a vast prospect for applications in the field of optics due to their unique electromagnetic tunable characteristics. In order to obtain an ultra-broadband high absorption material in the infrared region, we proposed a metal-dielectric-metal-dielectric-metal (MDMDM) metamaterial absorber using a titanium (Ti) nano-cross layer based on surface plasmon polariton (SPP) resonance and magnetic resonance cavity principles. The geometrical parameters of each layer have been examined carefully. The influence of incident angle from 0° to 60° is investigated for transverse electric and transverse magnetic plane-waves. Near-perfect absorption performance is achieved from near-infrared to mid-infrared region. The average absorption reaches as high as 97.41% from 2.05 to 6.08 μm. The absorber exhibits polarization-sensitive characteristics. The absorption peaks are 99.50% and 99.80% at 2.55 and 5.24 μm, respectively. The proposed material has potential applications in astronomical imaging, volcano and fire detection, remote sensing, biological monitoring, and other optical devices.
{"title":"Ultra-broadband infrared metamaterial absorber based on MDMDM structure for optical sensing","authors":"Fengjie Li, Jiansen Du, Shang Wang, Ruitao Yu, Xi Wang, Tiqiang Zhang, Zongtao Chi, Bin Wang, Ning Li","doi":"10.3389/fspas.2023.1338284","DOIUrl":"https://doi.org/10.3389/fspas.2023.1338284","url":null,"abstract":"Infrared observation is a crucial tool in the study of astronomical celestial bodies. Metamaterials have a vast prospect for applications in the field of optics due to their unique electromagnetic tunable characteristics. In order to obtain an ultra-broadband high absorption material in the infrared region, we proposed a metal-dielectric-metal-dielectric-metal (MDMDM) metamaterial absorber using a titanium (Ti) nano-cross layer based on surface plasmon polariton (SPP) resonance and magnetic resonance cavity principles. The geometrical parameters of each layer have been examined carefully. The influence of incident angle from 0° to 60° is investigated for transverse electric and transverse magnetic plane-waves. Near-perfect absorption performance is achieved from near-infrared to mid-infrared region. The average absorption reaches as high as 97.41% from 2.05 to 6.08 μm. The absorber exhibits polarization-sensitive characteristics. The absorption peaks are 99.50% and 99.80% at 2.55 and 5.24 μm, respectively. The proposed material has potential applications in astronomical imaging, volcano and fire detection, remote sensing, biological monitoring, and other optical devices.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"2 5","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-05DOI: 10.3389/fspas.2023.1337519
Jianguo Yan, Yue Wang
{"title":"Editorial: Recent progress from lunar, mars and asteroid missions","authors":"Jianguo Yan, Yue Wang","doi":"10.3389/fspas.2023.1337519","DOIUrl":"https://doi.org/10.3389/fspas.2023.1337519","url":null,"abstract":"","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"1 6","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-04DOI: 10.3389/fspas.2023.1325053
C. Ananna, Lucia Barbieri, Axel Boeltzig, Matteo Campostrini, Fausto Casaburo, G. F. Ciani, Alessandro Compagnucci, R. M. Gesuè, Jordan Marsh, E. Masha, Daniela Mercogliano, David Rapagnani, Duncan Robb, Ragandeep Singh Sidhu, J. Skowronski
The stellar evolution and chemical make-up of the Universe are determined by nuclear reactions occurring in a wide variety of stellar sites. Precise determinations of the cross sections of these reactions are crucial for the calculation of reaction rates and for the development of stellar evolution models. The Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration has been at the forefront of the direct measurement of nuclear reactions at the low energies of astrophysical interest for the last 35 years. The many significant results achieved at LUNA have been made possible due to the low background conditions uniquely available thanks to its location deep underground at the Laboratori Nazionali del Gran Sasso. Another key aspect of these successes is due to the experience of the LUNA collaboration in the production and characterization of a variety of solid targets used in reaction measurements. In this review, the main production techniques of solid targets are described, as well as the common methods adopted for target degradation monitoring. We also present the results of recent measurements using these targets and the future plans of the LUNA collaboration for measurements using solid targets at the LUNA400 kV and the new Ion Beam Facility (IBF) 3.5 MV are also presented.
恒星的演化和宇宙的化学构成是由发生在各种恒星部位的核反应决定的。精确测定这些反应的截面对于计算反应速率和建立恒星演化模型至关重要。在过去的 35 年里，地下核天体物理学实验室（LUNA）的合作一直处于直接测量天体物理学感兴趣的低能量核反应的前沿。地下核天体物理学实验室（LUNA）之所以能够取得许多重大成果，是因为它位于大萨索国家实验室（Laboratori Nazionali del Gran Sasso）的地下深处，具有得天独厚的低背景条件。这些成功的另一个关键因素是 LUNA 在生产和表征反应测量中使用的各种固体靶材方面积累了丰富的经验。在这篇综述中，我们将介绍固体靶材的主要生产技术，以及用于靶材降解监测的常用方法。我们还介绍了最近使用这些靶的测量结果，并介绍了 LUNA 合作组织未来在 LUNA400 kV 和新离子束设施 (IBF) 3.5 MV 使用固体靶进行测量的计划。
{"title":"Recent results and future perspectives with solid targets at LUNA","authors":"C. Ananna, Lucia Barbieri, Axel Boeltzig, Matteo Campostrini, Fausto Casaburo, G. F. Ciani, Alessandro Compagnucci, R. M. Gesuè, Jordan Marsh, E. Masha, Daniela Mercogliano, David Rapagnani, Duncan Robb, Ragandeep Singh Sidhu, J. Skowronski","doi":"10.3389/fspas.2023.1325053","DOIUrl":"https://doi.org/10.3389/fspas.2023.1325053","url":null,"abstract":"The stellar evolution and chemical make-up of the Universe are determined by nuclear reactions occurring in a wide variety of stellar sites. Precise determinations of the cross sections of these reactions are crucial for the calculation of reaction rates and for the development of stellar evolution models. The Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration has been at the forefront of the direct measurement of nuclear reactions at the low energies of astrophysical interest for the last 35 years. The many significant results achieved at LUNA have been made possible due to the low background conditions uniquely available thanks to its location deep underground at the Laboratori Nazionali del Gran Sasso. Another key aspect of these successes is due to the experience of the LUNA collaboration in the production and characterization of a variety of solid targets used in reaction measurements. In this review, the main production techniques of solid targets are described, as well as the common methods adopted for target degradation monitoring. We also present the results of recent measurements using these targets and the future plans of the LUNA collaboration for measurements using solid targets at the LUNA400 kV and the new Ion Beam Facility (IBF) 3.5 MV are also presented.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"58 23","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139385763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.3389/fspas.2023.1233060
G. Fasel, L. C. Lee, E. Lake, D. Csonge, B. Yonano, O. Bradley, J. Briggs, S. H. Lee, J. Mann, F. Sigernes, D. Lorentzen
In 1961, Dungey suggested that magnetic reconnection occurs due to the solar-terrestrial interaction. The interplanetary magnetic field (IMF) is thought to merge with Earth’s geomagnetic field (GMF). After the reconnection process the newly formed magnetic flux tube, consisting of both the IMF and GMF, moves anti-sunward. Poleward-moving auroral forms (PMAFs) are believed to be the ionospheric signatures of this process, which transfers magnetic flux from the dayside to the nightside. This paper looks at the connection between the solar wind speed and the motion of the PMAF as it moves from the auroral oval, anti-sunward, into the polar cap. PMAFs are identified using both the meridian scanning photometer (MSP) and colored all-sky camera (ASC). Once the PMAFs are identified, the PMAF-SLOPE, vα (units of degrees per time) and the angle (αPMAF) the PMAF makes with the horizontal (Time axis), in the MSP plot are calculated. These values (vα and αPMAF) are individually plotted against the vx-component of the solar wind speed and the flow speed (total solar wind speed). The plots generate linear a relationship between PMAF-SLOPEs, vα, [or PMAF angles (αPMAF)], and the vx-component of the solar wind speed (or the flow speed). A total of 57 PMAF events from 8 different days were associated with solar wind speeds (vx-component) ranging from 344 to 679 km/s. The first linear plot, between the PMAF-SLOPE and solar wind speed (vx-component), shows a high correlation: rvα=0.944. A second linear plot, between αPMAF and the solar wind speed (vx-component) shows a very high correlation: rαPMAF=0.973. The conclusions obtained from this statistical study are: 1) both the PMAF-SLOPE vα and αPMAF are highly correlated to the vx-component of the solar wind, increasing when vx increases and vice versa, 2) PMAFs must be connected to both the IMF and GMF and are dragged anti-sunward, mostly by the vx-component of the solar wind, and 3) PMAFs are indeed the ionospheric footprints of a newly formed magnetic flux tube, due to dayside magnetic reconnection, being transferred from the dayside to nightside.
{"title":"Correlation between the solar wind speed and the passage of poleward-moving auroral forms into the polar cap","authors":"G. Fasel, L. C. Lee, E. Lake, D. Csonge, B. Yonano, O. Bradley, J. Briggs, S. H. Lee, J. Mann, F. Sigernes, D. Lorentzen","doi":"10.3389/fspas.2023.1233060","DOIUrl":"https://doi.org/10.3389/fspas.2023.1233060","url":null,"abstract":"In 1961, Dungey suggested that magnetic reconnection occurs due to the solar-terrestrial interaction. The interplanetary magnetic field (IMF) is thought to merge with Earth’s geomagnetic field (GMF). After the reconnection process the newly formed magnetic flux tube, consisting of both the IMF and GMF, moves anti-sunward. Poleward-moving auroral forms (PMAFs) are believed to be the ionospheric signatures of this process, which transfers magnetic flux from the dayside to the nightside. This paper looks at the connection between the solar wind speed and the motion of the PMAF as it moves from the auroral oval, anti-sunward, into the polar cap. PMAFs are identified using both the meridian scanning photometer (MSP) and colored all-sky camera (ASC). Once the PMAFs are identified, the PMAF-SLOPE, vα (units of degrees per time) and the angle (αPMAF) the PMAF makes with the horizontal (Time axis), in the MSP plot are calculated. These values (vα and αPMAF) are individually plotted against the vx-component of the solar wind speed and the flow speed (total solar wind speed). The plots generate linear a relationship between PMAF-SLOPEs, vα, [or PMAF angles (αPMAF)], and the vx-component of the solar wind speed (or the flow speed). A total of 57 PMAF events from 8 different days were associated with solar wind speeds (vx-component) ranging from 344 to 679 km/s. The first linear plot, between the PMAF-SLOPE and solar wind speed (vx-component), shows a high correlation: rvα=0.944. A second linear plot, between αPMAF and the solar wind speed (vx-component) shows a very high correlation: rαPMAF=0.973. The conclusions obtained from this statistical study are: 1) both the PMAF-SLOPE vα and αPMAF are highly correlated to the vx-component of the solar wind, increasing when vx increases and vice versa, 2) PMAFs must be connected to both the IMF and GMF and are dragged anti-sunward, mostly by the vx-component of the solar wind, and 3) PMAFs are indeed the ionospheric footprints of a newly formed magnetic flux tube, due to dayside magnetic reconnection, being transferred from the dayside to nightside.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"3 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-22DOI: 10.3389/fspas.2023.1244402
Katya Georgieva, Svetlana Veretenenko
The influence of the Sun on the Earth’s atmosphere and climate has been a matter of hot debate for more than two centuries. In spite of the correlations found between the sunspot numbers and various atmospheric parameters, the mechanisms for such influences are not quite clear yet. Though great progress has been recently made, a major problem remains: the correlations are not stable, they may strengthen, weaken, disappear, and even change sign depending on the time period. None of the proposed so far mechanisms explains this temporal variability. The basis of all solar activity is the solar magnetic field which cyclically oscillates between its two components—poloidal and toroidal. We first briefly describe the operation of the solar dynamo transforming the poloidal field into toroidal and back, the evaluated relative variations of these two components, and their geoeffective manifestations. We pay special attention to the reconstruction of the solar irradiance as the key natural driver of climate. We point at some problems in reconstructing the long-term irradiance variations and the implications of the different irradiance composite series on the estimation of the role of the Sun in climate change. We also comment on the recent recalibration of the sunspot number as the only instrumentally measured parameter before 1874, and therefore of crucial importance for reconstructing the solar irradiance variations and their role in climate change. We summarize the main proposed mechanisms of solar influences on the atmosphere, and list some of the modelling and experimental results either confirming or questioning them. Two irradiance-driven mechanisms have been proposed. The “bottom-up” mechanism is based on the enhanced absorption of solar irradiance by the oceans in relatively cloud-free equatorial and subtropical regions, amplified by changes in the temperature gradients, circulation, and cloudiness. The “top-down” mechanism involves absorption by the stratospheric ozone of solar UV radiation whose variability is much greater than that of the visible one, and changes of large-scale circulation patterns like the stratospheric polar vortex and the tropospheric North Atlantic Oscillation. The positive phase of the tropospheric North Atlantic Oscillation indicative of a strong vortex is found to lag by a couple of years the enhanced UV in Smax. It was however shown that this positive response is not due to lagged UV effects but instead to precipitating energetic particles which also peak a couple of years after Smax. The solar wind and its transients modulate the flux of galactic cosmic rays which are the main source of ionization of the Earth’s atmosphere below ∼50 km. This modulation leads to modulation of the production of aerosols which are cloud condensation nuclei, and to modulation of cloudiness. Increased cloudiness decreases the solar irradiance reaching the low atmosphere and the Earth’s surface. Variations of the galactic cosmic rays also le
{"title":"Solar influences on the Earth’s atmosphere: solved and unsolved questions","authors":"Katya Georgieva, Svetlana Veretenenko","doi":"10.3389/fspas.2023.1244402","DOIUrl":"https://doi.org/10.3389/fspas.2023.1244402","url":null,"abstract":"The influence of the Sun on the Earth’s atmosphere and climate has been a matter of hot debate for more than two centuries. In spite of the correlations found between the sunspot numbers and various atmospheric parameters, the mechanisms for such influences are not quite clear yet. Though great progress has been recently made, a major problem remains: the correlations are not stable, they may strengthen, weaken, disappear, and even change sign depending on the time period. None of the proposed so far mechanisms explains this temporal variability. The basis of all solar activity is the solar magnetic field which cyclically oscillates between its two components—poloidal and toroidal. We first briefly describe the operation of the solar dynamo transforming the poloidal field into toroidal and back, the evaluated relative variations of these two components, and their geoeffective manifestations. We pay special attention to the reconstruction of the solar irradiance as the key natural driver of climate. We point at some problems in reconstructing the long-term irradiance variations and the implications of the different irradiance composite series on the estimation of the role of the Sun in climate change. We also comment on the recent recalibration of the sunspot number as the only instrumentally measured parameter before 1874, and therefore of crucial importance for reconstructing the solar irradiance variations and their role in climate change. We summarize the main proposed mechanisms of solar influences on the atmosphere, and list some of the modelling and experimental results either confirming or questioning them. Two irradiance-driven mechanisms have been proposed. The “bottom-up” mechanism is based on the enhanced absorption of solar irradiance by the oceans in relatively cloud-free equatorial and subtropical regions, amplified by changes in the temperature gradients, circulation, and cloudiness. The “top-down” mechanism involves absorption by the stratospheric ozone of solar UV radiation whose variability is much greater than that of the visible one, and changes of large-scale circulation patterns like the stratospheric polar vortex and the tropospheric North Atlantic Oscillation. The positive phase of the tropospheric North Atlantic Oscillation indicative of a strong vortex is found to lag by a couple of years the enhanced UV in Smax. It was however shown that this positive response is not due to lagged UV effects but instead to precipitating energetic particles which also peak a couple of years after Smax. The solar wind and its transients modulate the flux of galactic cosmic rays which are the main source of ionization of the Earth’s atmosphere below ∼50 km. This modulation leads to modulation of the production of aerosols which are cloud condensation nuclei, and to modulation of cloudiness. Increased cloudiness decreases the solar irradiance reaching the low atmosphere and the Earth’s surface. Variations of the galactic cosmic rays also le","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"50 14","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138946151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-22DOI: 10.3389/fspas.2023.1322934
L. Gan, Wen Li, Mirek Hanzelka, Qianli Ma, Jay M. Albert, Anton Artemyev
Resonant interactions with whistler-mode waves are a crucial mechanism that drives the precipitation of energetic electrons. Using test particle simulations, we investigated the impact of nonlinear interactions of whistler-mode waves on electron precipitation across a broad energy range (10 keV- 1 MeV). Specifically, we focused on the combined effects of conventional phase bunching and anomalous scattering, which includes anomalous trapping and positive bunching. It is shown that anomalous scattering transports electrons away from the loss cone and the only process directly causing precipitation in the nonlinear regime is the phase bunching. We further show that their combined effects result in a precipitation-to-trapped flux ratio lower than the quasilinear expectations in a quasi-equilibrium state. Additionally, we calculated the diffusion and advection coefficients associated with the nonlinear trapping and bunching processes, which are vital for understanding the underlying mechanisms of the precipitation. Based on these coefficients, we characterized the phase bunching boundary, representing the innermost pitch angle boundary where phase bunching can occur. A further analysis revealed that electrons just outside this boundary, rather than near the loss cone, are directly precipitated, while electrons within the boundary are prevented from precipitation due to anomalous scattering. Moreover, we demonstrated that the regime of dominant nonlinear precipitation is determined by the combination of the phase bunching boundary and the inhomogeneity ratio. This comprehensive analysis provides insights into the nonlinear effects of whistler-mode waves on electron precipitation, which are essential for understanding physical processes related to precipitation, such as microbursts, characterized by intense and bursty electron precipitation.
{"title":"Electron precipitation caused by intense whistler-mode waves: combined effects of anomalous scattering and phase bunching","authors":"L. Gan, Wen Li, Mirek Hanzelka, Qianli Ma, Jay M. Albert, Anton Artemyev","doi":"10.3389/fspas.2023.1322934","DOIUrl":"https://doi.org/10.3389/fspas.2023.1322934","url":null,"abstract":"Resonant interactions with whistler-mode waves are a crucial mechanism that drives the precipitation of energetic electrons. Using test particle simulations, we investigated the impact of nonlinear interactions of whistler-mode waves on electron precipitation across a broad energy range (10 keV- 1 MeV). Specifically, we focused on the combined effects of conventional phase bunching and anomalous scattering, which includes anomalous trapping and positive bunching. It is shown that anomalous scattering transports electrons away from the loss cone and the only process directly causing precipitation in the nonlinear regime is the phase bunching. We further show that their combined effects result in a precipitation-to-trapped flux ratio lower than the quasilinear expectations in a quasi-equilibrium state. Additionally, we calculated the diffusion and advection coefficients associated with the nonlinear trapping and bunching processes, which are vital for understanding the underlying mechanisms of the precipitation. Based on these coefficients, we characterized the phase bunching boundary, representing the innermost pitch angle boundary where phase bunching can occur. A further analysis revealed that electrons just outside this boundary, rather than near the loss cone, are directly precipitated, while electrons within the boundary are prevented from precipitation due to anomalous scattering. Moreover, we demonstrated that the regime of dominant nonlinear precipitation is determined by the combination of the phase bunching boundary and the inhomogeneity ratio. This comprehensive analysis provides insights into the nonlinear effects of whistler-mode waves on electron precipitation, which are essential for understanding physical processes related to precipitation, such as microbursts, characterized by intense and bursty electron precipitation.","PeriodicalId":46793,"journal":{"name":"Frontiers in Astronomy and Space Sciences","volume":"5 5","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138944637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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