Astrophysics and Space Science最新文献_第8页

The influence of magnetic field parameters and time step on deep learning models of solar flare prediction 磁场参数和时间步长对太阳耀斑预测深度学习模型的影响

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-05-15 DOI: 10.1007/s10509-024-04314-6

Jinfang Wei, Yanfang Zheng, Xuebao Li, Changtian Xiang, Pengchao Yan, Xusheng Huang, Liang Dong, Hengrui Lou, Shuainan Yan, Hongwei Ye, Xuefeng Li, Shunhuang Zhang, Yexin Pan, Huiwen Wu

{"title":"The influence of magnetic field parameters and time step on deep learning models of solar flare prediction","authors":"Jinfang Wei, Yanfang Zheng, Xuebao Li, Changtian Xiang, Pengchao Yan, Xusheng Huang, Liang Dong, Hengrui Lou, Shuainan Yan, Hongwei Ye, Xuefeng Li, Shunhuang Zhang, Yexin Pan, Huiwen Wu","doi":"10.1007/s10509-024-04314-6","DOIUrl":"10.1007/s10509-024-04314-6","url":null,"abstract":"<div>The research on solar flare predicting holds significant practical and scientific value for safeguarding human activities. Current solar flare prediction models have not fully considered important factors such as time step length, nor have they conducted a comparative analysis of the physical features in multiple models or explored the consistency in the importance of features. In this work, based on SHARP data from SDO, we build 9 machine learning-based solar flare prediction models for binary “Yes” or “No” class prediction within the next 24 hours, and study the impact of different time steps and other factors on the forecasting performance. The main results are as follows. (1) The predictive performance of eight deep learning models shows an increasing trend as the time step length increases, and the models perform the best at the length of 40. (2) In predicting solar flares of ≥C class and ≥M class, the True Skill Statistic(TSS) of deep learning models consistently outperforms that of baseline model. For the same model, the TSS for predicting ≥M class flares generally exceeds that for predicting ≥C class flares. (3) The Brier Skill Score (BSS) of deep learning models significantly surpasses that of baseline model in predicting ≥C class flares. However, the BSS scores of the nine models are comparable for predicting ≥M class flares. For the same model, the BSS for predicting ≥C class flares is generally higher than that for predicting ≥M class flares. (4) Through feature importance analysis of multiple models, the common features that consistently rank at the top and bottom are identified.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141038115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

The group height of spicules links their acceleration and velocity 孢子的群体高度与其加速度和速度有关

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-05-14 DOI: 10.1007/s10509-024-04308-4

Leonard A. Freeman

{"title":"The group height of spicules links their acceleration and velocity","authors":"Leonard A. Freeman","doi":"10.1007/s10509-024-04308-4","DOIUrl":"10.1007/s10509-024-04308-4","url":null,"abstract":"<div>This study reveals a new feature of many solar jets: a group height, which links their acceleration and velocity.The acceleration and velocity ((a), (V)) for jets such as spicules, often displayed as scattergraphs, show a strong correlation. This can be represented empirically by the equation, (V = pa + q), where (p) and (q ) are two arbitrary non-zero constants.This study reanalyses the ((a), (V)) data for nine different groups of jets, in order to test an alternative proposal that a simpler relationship directly links ((a), (V)) to the mean height for the group of jets, without needing the empirical constants (p ) and (q). A standard mathematical test – plotting log((a)) against log((V)), tests whether (V sim a^{n}) and if so, gives the value of n. When this is done for a wide range of jets the index (n) is consistently found to be close to 0.5The nine groups of jets include spicules, macrospicules and dynamic fibrils. The result, (V sim a)0.5, or equivalently (V^{2} = ka), with only one constant, provides as close a match to the data as the equation (V = pa + q), which requires two unknown constants. It is found that the constant (k), is a known quantity: just twice the mean height, (overline{s}), of the group of jets being analysed. This then gives the equation (V^{2} =2 a overline{s}), for the jets in the group. This more succinct relationship links the acceleration and maximum velocity of every jet in the group to a well-defined quantity – the mean height of the group of spicules, without needing extra constants</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Geomagnetic disturbance of the meridian chain at mid and low latitudes during 2015 geomagnetic storms 2015 年地磁暴期间中低纬度子午线链的地磁扰动

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-05-13 DOI: 10.1007/s10509-024-04309-3

Xinxin Ma, Zhan Lin, Xizheng Wang, Qi Li, Suqin Zhang

{"title":"Geomagnetic disturbance of the meridian chain at mid and low latitudes during 2015 geomagnetic storms","authors":"Xinxin Ma, Zhan Lin, Xizheng Wang, Qi Li, Suqin Zhang","doi":"10.1007/s10509-024-04309-3","DOIUrl":"10.1007/s10509-024-04309-3","url":null,"abstract":"<div>This paper presented an analysis of geomagnetic disturbance observed on the ground during geomagnetic storms with different intensities in 2015 using the meridian chain data at geomagnetic mid and low latitudes. Ground observation records superimpose varying types of space-current system and noise interference. Geomagnetic disturbance with variation of discontinuity and irregularities are difficult to identify and distinguish. We proposed a variational mode decomposition (VMD) algorithm for reconstructing geomagnetic horizontal ((H)) disturbance signals. We decomposed the geomagnetic signals into geomagnetic disturbance signals, diurnal variation signals, and noise disturbance signals using the VMD algorithm. Intrinsic mode functions (IMFs) were selected to form the reconstructed signal, which represented a geomagnetic disturbance during a geomagnetic storm. We investigated the decreased amplitude of (H) component obtained from the reconstructed signals during main phase of geomagnetic storms with different geomagnetic storms intensities and seasons at mid and low latitudes. The maximum values of gradient variation of (H ) component disturbance with geomagnetic latitude cosine are near magnetic latitude 30°N during geomagnetic storms with different intensities and seasons. Ionopheric structural changes in the low-to-mid latitude transition zone maybe the primary cause. The result provides a reference for the complex coupling relationship between the ionosphere and magnetosphere during geomagnetic storms.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

On the variation of small-amplitude Forbush decreases with solar-geomagnetic parameters 关于小振幅福布什下降随太阳地磁参数的变化

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-05-08 DOI: 10.1007/s10509-024-04310-w

Chukwuebuka J. Ugwu, Ogbonnaya Okike, Firew M. Menteso, Jibrin A. Alhassan, Dominic C. Obiegbuna, Augustine E. Chukwude, Romanus E. Ugwoke, Evaristus U. Iyida, Innocent O. Eya, Ugochukwu C. Enwelum, Orji P. Orji

{"title":"On the variation of small-amplitude Forbush decreases with solar-geomagnetic parameters","authors":"Chukwuebuka J. Ugwu, Ogbonnaya Okike, Firew M. Menteso, Jibrin A. Alhassan, Dominic C. Obiegbuna, Augustine E. Chukwude, Romanus E. Ugwoke, Evaristus U. Iyida, Innocent O. Eya, Ugochukwu C. Enwelum, Orji P. Orji","doi":"10.1007/s10509-024-04310-w","DOIUrl":"10.1007/s10509-024-04310-w","url":null,"abstract":"<div>Detection of weak signals remains challenging in astrophysics. This is particularly applicable in the investigation of Forbush events. There is thus, a paucity of catalogs of small-amplitude Forbush decreases (FDs). Detail investigations of the space-weather implications of small FDs are, thus, lacking in the literature. Recently, large catalogs of weak FDs, for the first time, have been published. This work employs the newly created lists of small-amplitude FDs to investigate the statistical link between small FDs and solar-geomagnetic variables. The solar-geomagnetic variables were obtained from the OMNI database. A simple coincident R software code was employed in matching the related solar-geomagnetic variables with the weak Forbush events. The FD dates were taken as the input signal. Scatter plots of FDs against interplanetary magnetic field (IMF), solar wind speed (SWS), planetary K-index (Kp) and planetary A-index (Ap) reveal a negative relationship, while that of FDs against disturbance storm time index (Dst) shows a positive relationship. Statistical significance of these relations were tested. The small-amplitude FDs and solar-geomagnetic variables at Potchefstroom (PTFM) station register statistically significant relations. Non-statistically significant correlation between the small-amplitude FDs and solar-geomagnetic variables were obtained at South Pole (SOPO) station, with the exception of FD-SWS that reveals statistically significant correlation. The differences in the correlation results obtained at the two stations (PTFM and SOPO) could be attributed to the differences in the characteristics of the NM stations. These results suggest that geomagnetic storm indices play important role in the evolution of FDs.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140941719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Dynamics of nonlinear ion-acoustic waves in Venus’ lower ionosphere 金星低层电离层中的非线性离子声波动力学

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-05-06 DOI: 10.1007/s10509-024-04295-6

Kusum Chettri, Jharna Tamang, Prasanta Chatterjee, Asit Saha

{"title":"Dynamics of nonlinear ion-acoustic waves in Venus’ lower ionosphere","authors":"Kusum Chettri, Jharna Tamang, Prasanta Chatterjee, Asit Saha","doi":"10.1007/s10509-024-04295-6","DOIUrl":"10.1007/s10509-024-04295-6","url":null,"abstract":"<div>Dynamics of nonlinear ion-acoustic waves (IAWs) are studied for Venus’ lower atmosphere at an altitude of (200-1000) km. Two-soliton, nonlinear solitary and periodic waves in a three-component plasma consisting of (H^{+}) and (O^{+}) ions with kappa distributed electrons are studied. Using the reductive perturbation technique (RPT), the Korteweg-de Vries (KdV) equation is derived and a Planar dynamical system is formed for the KdV equation using a travelling wave transformation. A phase portrait is drawn to analyze nonlinear wave behaviors by adjusting the parameters (kappa ) (spectral index), (gamma ) (unperturbed number density ratio), and (V) (travelling wave speed). Increasing values of (kappa ) amplify amplitudes for solitary and periodic waves, narrow down the width of the solitary wave, and broaden the width of the periodic wave. Increasing value of (gamma ) boosts amplitude of the solitary wave with unchanged width, while amplitude of the nonlinear periodic wave decreases and width widens. Increasing value of (V) enhances amplitudes and reduces widths for both solitary and periodic waves. Two-soliton solutions for the KdV equation are studied using the Hirota direct method. Increasing value of (gamma ) reduces amplitude of the soliton without affecting the width and increasing value of (kappa ) reduces width of the soliton. Phase shift for two-soliton is also shown and found that for different values of (kappa ), the phase shift increases on increasing value of (gamma ). The findings of our result aid in understanding the dynamics of nonlinear waves and two-soliton solutions in Venus’ lower ionosphere.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140889635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

The spectral evolution of white dwarfs: where do we stand? 白矮星的光谱演变：我们的现状如何？

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-04-26 DOI: 10.1007/s10509-024-04307-5

Antoine Bédard

{"title":"The spectral evolution of white dwarfs: where do we stand?","authors":"Antoine Bédard","doi":"10.1007/s10509-024-04307-5","DOIUrl":"10.1007/s10509-024-04307-5","url":null,"abstract":"<div>White dwarfs are the dense, burnt-out remnants of the vast majority of stars, condemned to cool over billions of years as they steadily radiate away their residual thermal energy. To first order, their atmosphere is expected to be made purely of hydrogen due to the efficient gravitational settling of heavier elements. However, observations reveal a much more complex situation, as the surface of a white dwarf (1) can be dominated by helium rather than hydrogen, (2) can be polluted by trace chemical species, and (3) can undergo significant composition changes with time. This indicates that various mechanisms of element transport effectively compete against gravitational settling in the stellar envelope. This phenomenon is known as the spectral evolution of white dwarfs and has important implications for Galactic, stellar, and planetary astrophysics. This invited review provides a comprehensive picture of our current understanding of white dwarf spectral evolution. We first describe the latest observational constraints on the variations in atmospheric composition along the cooling sequence, covering both the dominant and trace constituents. We then summarise the predictions of state-of-the-art models of element transport in white dwarfs and assess their ability to explain the observed spectral evolution. Finally, we highlight remaining open questions and suggest avenues for future work.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10509-024-04307-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Hilbert repulsion in the Kerr–Newman anti-de Sitter spacetime 克尔-纽曼反德西特时空中的希尔伯特斥力

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-04-22 DOI: 10.1007/s10509-024-04304-8

Chiging Lasa Polo, Heisnam Shanjit Singh

引用次数: 0

Variable Chaplygin gas: Constraining parameters using FRBs 可变查普利金气体：利用 FRB 限制参数

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-04-22 DOI: 10.1007/s10509-024-04306-6

Geetanjali Sethi, Udish Sharma, Nadia Makhijani

{"title":"Variable Chaplygin gas: Constraining parameters using FRBs","authors":"Geetanjali Sethi, Udish Sharma, Nadia Makhijani","doi":"10.1007/s10509-024-04306-6","DOIUrl":"10.1007/s10509-024-04306-6","url":null,"abstract":"<div>We investigate cosmological constraints on the Variable Chaplygin gas model parameters with latest observational data of the Fast Radio Bursts and compare the results with previous constraints obtained using SNe Ia (Pantheon+SHOES), Gamma Ray Bursts, Baryon Acoustic Oscillations and Hubble parameter observational data. The Variable Chaplygin gas model is shown to be compatible with these datasets. We have obtained tighter constraints on model parameters (B_{s}) and (n), using the FRB data set. By using the Markov chain Monte Carlo (MCMC) method we obtain, (B_{s})=(0.18pm 0.10), (n=1.10pm 1.15) and (H_{0})= (70.46pm 0.66) with the SNe Ia data set, (B_{s})= (0.09pm 0.06), (n= 0.44pm 0.89 ) and (H_{0}=70.57pm 0.64 ) with the FRB data set, (B_{s})=(0.16pm 0.11), (n=1.06pm 1.25) and (H_{0})= (70.37pm 0.65) with the BAO data set, (B_{s})=(0.05pm 0.000), (n=1.46pm 0.23) and (H_{0})= (70.21pm 0.57) with the H(z) data set and (B_{s})=(0.20pm 0.11), (n=1.25pm 1.17) and (H_{0})= (70.37pm 0.64) with the GRB data set. A good agreement for (H_{0}) is observed from these data sets.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"369 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Trajectory optimization of flybys of multiple irregular satellites of Jupiter with Galilean moons gravity assist 利用伽利略卫星的重力辅助优化飞越木星多颗不规则卫星的轨迹

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-04-19 DOI: 10.1007/s10509-024-04305-7

Quan Jing, Zhixin Hao, Mingtao Li

引用次数: 0

Thrust continuation of time-optimal orbital transfers with soft terminal conditions 具有软终端条件的时间最优轨道转移的推力延续

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2024-04-12 DOI: 10.1007/s10509-024-04303-9

Yang Wang, Xiyun Hou, Francesco Topputo

引用次数: 0