检索结果-南通市图书馆

Solar Flare Forecast Model Based on Resampling and Fusion Method

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第8期22卷 238-248页

作者： Jie Wan Jun-Feng Fu Dai-Min Tan Ke Han Meng-Yao Yu Peng E Laboratory for Space Environment and Physical Sciences Harbin Institute of TechnologyHarbin 150001China School of Electrical Engineering and Automation Harbin Institute of TechnologyHarbin 150001China School of Computer and Information Engineering Harbin University of CommerceHarbin 150028China

Predicting the activity of solar flares is of great significance for studying its physical mechanism and the impact on human production and life.Problems such as class imbalance,high time-series sensitivity,and over-localization of important features exist in the sample data used for flare forecasting.We design a solar flare fusion method based on resampling and the CNN-GRU algorithm to try to solve the above problems.In order to verify the effectiveness of this fusion method,first,we compared the forecast performance of different resampling methods by keeping the forecast model unchanged.Then,we used the resampling algorithm with high performance to combine some single forecast models and fusion forecast models respectively.We use the 2010-2017 sunspot data set to train and test the performance of the flare model in predicting flare events in the next 48 h.Through the conclusion of the above steps,we prove that the resampling method SMOTE and its variant SMOTE-ENN are more advantageous in class imbalance problem of flare samples.In addition,after the fusion of one-dimensional convolution and recurrent network with"forget-gate",combined with the SMOTE-ENN to achieve TSS=61%,HSS=61%,TP_(Rate)=77%and TN_(Rate)=83%.This proves that the fusion model based on resampling and the CNN-GRU algorithm is more suitable for solar flare forecasting.

关键词： (sun:)sunspots sun:flares sun:X-rays gamma-rays sun:magnetic fields sun:corona

Temperature Analysis of Flaring(AR 11283)and Non-flaring(AR 12194)coronal Loops

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第3期22卷 143-156页

作者： Narges Fathalian Seyedeh Somayeh Hosseini Rad Nasibeh Alipour Hossein Safari Department of Physics Payame Noor University(PNU)P.O.Box 19395-3697TehranIran Department of Physics Faculty of ScienceUniversity of ZanjanP.O.Box 45195-313ZanjanIran

Here,we study the temperature structure of flaring and non-flaring coronal loops,using extracted loops from images taken in six extreme ultraviolet channels recorded by Atmospheric Imaging Assembly/Solar Dynamics Observatory.We use data for loops of an X2.1-class-flaring active region(AR 11283)during 22:10 UT until 23:00 UT,on 2011 September 6;and a non-flaring active region(AR 12194)during 08:00:00 UT until 09:00:00 UT on2014 October 26.By using the spatially synthesized Gaussian differential emission measure(DEM)forward-fitting method,we calculate the peak temperatures for each strip of the loops.We apply the Lomb–Scargle method to compute the oscillation periods for the temperature series of each strip.The periods of the temperature oscillations for the flaring loops ranged from 7 to 28.4 minutes.These temperature oscillations show very close behavior to the slow-mode oscillation.We observe that the temperature oscillations in the flaring loops started at least around10 minutes before the transverse oscillations and continue for a long time duration even after the transverse oscillations ended.The temperature amplitudes increased during the flaring time(20 minutes)in the flaring loops.The periods of the temperatures obtained for the non-flaring loops ranged from 8.5 to 30 minutes,but their significances are less(below 0.5)in comparison with the flaring ones(near to one).Hence the detected temperature periods for the non-flaring loops’strips are less probable in comparison with the flaring ones,and maybe they are just fluctuations.Based on our confined observations,it seems that the flaring loops’periods show more diversity and their temperatures have wider ranges of variation than the non-flaring ones.More accurate commentary in this respect requires more extensive statistical research and broader observations.

关键词： sun:flares sun:corona sun:oscillations stars:imaging stars:solar-type

On the Relation Between coronal Green Line Brightness and Magnetic Fields Intensity

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第7期22卷 128-138页

作者： Xue-Fei Zhang Yu Liu Ming-Yu Zhao Teng-Fei Song Jing-Xing Wang Xiao-Bo Li Zi-Han Li Yunnan Observatories Chinese Academy of SciencesKunming 650011China University of Chinese Academy of Sciences Beijing 100049China Yunnan Normal University School of Physics and Electronic InformationKunming 650000China

Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the higher coronal magnetic field intensity may correspond to.To try to further reveal the relationship between coronal green line brightness and magnetic field intensity,we use the 2 D coronal images observed by Yunnan Observatories Greenline Imaging System(YOGIS) of the 10 cm Lijiang coronagraph and the coronal magnetic field maps calculated from the current-free extrapolations with the photospheric magnetograms taken by Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO) spacecraft.In our analysis,we identified the coronal loop structures and construct two-dimensional maps of the corresponding magnetic field intensity in the plane of the sky(POS) above the limb.We derive the correlation coefficients between the coronal brightness and the magnetic field intensity for different heights of coronal layers.We further use a linear combination of a Gaussian and a quadratic profile to fit the correlation coefficients distribution,finding a largest correlation coefficient of 0.82 near 1.1 R(solar radii) where is almost the top of the closed loop system.For the small closed loop system identified,the correlation coefficient distributions crossing and covering the loop are calculated.We also investigate the correlation with extended heliocentric latitude zones and long period of one whole Carrington Rotation,finding again that the maximum correlation coefficient occurs at the same height.It is the first time for us to find that the correlation coefficients are high(all are larger than 0.8) at the loop-tops and showing poor correlation coefficients with some fluctuations near the feet of the coronal loops.Our findings indicate that,for the heating of the low-latitude closed loops,both DC(dissipation of currents) and AC(dissipation of Alfvén and magnetosonic waves) mechanisms should act

关键词： sun:magnetic fields sun:corona Stars:coronae sun:activity sun:atmosphere sun:coronal mass ejections(CMEs) sun:fundamental parameters sun:heliosphere sun:UV radiation

Simultaneous Detection of Flare-related Decaying and Decayless Kink Oscillations Using Jerk-aware Motion Magnification

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第11期22卷 130-136页

作者： Xiaowei Guo Bo Liang Song Feng Wei Dai Yunfei Yang Faculty of Information Engineering and Automation Kunming University of Science and TechnologyKunming 650500China

Kink oscillations of coronal loops are often influenced by external events and this results in various changes of the oscillations.Studying the changes can provide valuable information for understanding kink oscillations.Our observation focuses on a flare region acquired by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory spacecraft on 2016 March 23.There are a bunch of arched loops and an open loop near the region.However,their oscillations show very low amplitudes.So we used the jerk-aware motion method to magnify the weak oscillations.We found that before the flare onset at 02:59 UT,there were some large loops above the arched loops being raised rapidly.The properties of the weak oscillations show clear changes.On the one hand,the oscillations in the arched loops were decayless initially,but both their amplitude and period increased after 02:30 UT and before the flare onset.Once enhanced,the oscillations decayed with time.On the other hand,the oscillations in the open loop were nearly constant before and after 02:30 UT,but their period increased.This means that the changes in periods and amplitudes of oscillations are likely associated with the loops raised before the flare.

关键词： sun:corona sun:oscillations sun:flares waves

Obtaining space-based SDO/AIA solar UV and EUV images from ground-based Hαobservations by deep learning

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第6期21卷 233-240页

作者：刘铁宿英娜徐黎明季海生 Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Jiangsu Urban and Rural Construction College Changzhou 213147China

In this work,we explore the mappings from solar images taken in Hα(6563 A)by the Global Oscillation Network Group(GONG)on the ground to those observed in eight different wavelengths(94,131,171,193,211,304,335 and 1600 A)by SDO/AIA in space.Eight mappings are built by training the conditional Generative Adversarial Networks(cGANs)on datasets with 500 paired images,which are[Hα,AIA94],[Hα,AIA131],[Hα,AIA171],[Hα,AIA193],[Hα,AIA211],[Hα,AIA304],[Hα,AIA335]and[Hα,AIA1600].We evaluate the eight trained cGANs models on validation and test datasets with 154-pair images and 327-pair images,respectively.The model generated fake AIA images match the corresponding observed AIA images well on large-scale structures such as large active regions and prominences.But the small-scale flare loops and filament threads are difficult to reconstruct.Four quantitative comparisons are carried out on the validation and test datasets to score the mappings.We find that the model-generated images in 304 and 1600 A match the corresponding observed images best.This exploration suggests that the cGANs are promising methods for mappings between ground-based Ha and space-based EUV/UV images,while some improvements are necessary.

关键词： methods:analytical techniques:image processing sun:corona sun:UV radiation

Magnetic flux ropes in the solar corona: structure and evolution toward eruption

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第10期20卷 287-328页

作者： Rui Liu CAS Key Laboratory of Geospace Environment Department of Geophysics and Planetary SciencesUniversity of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology Hefei 230026China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaMengcheng 233500China

Magnetic flux ropes are characterized by coherently twisted magnetic field lines,which are ubiquitous in magnetized plasmas.As the core structure of various eruptive phenomena in the solar atmosphere,flux ropes hold the key to understanding the physical mechanisms of solar eruptions,which impact the heliosphere and planetary atmospheres.The strongest disturbances in the Earth’s space environments are often associated with large-scale flux ropes from the sun colliding with the Earth’s magnetosphere,leading to adverse,sometimes catastrophic,space-weather effects.However,it remains elusive as to how a flux rope forms and evolves toward eruption,and how it is structured and embedded in the ambient field.The present paper addresses these important questions by reviewing current understandings of coronal flux ropes from an observer’s perspective,with an emphasis on their structures and nascent evolution toward solar eruptions,as achieved by combining observations of both remote sensing and in-situ detection with modeling and simulation.This paper highlights an initiation mechanism for coronal mass ejections(CMEs)in which plasmoids in current sheets coalesce into a’seed’flux rope whose subsequent evolution into a CME is consistent with the standard model,thereby bridging the gap between microscale and macroscale dynamics.

关键词： magnetic fields magnetic reconnection sun:magnetic fields sun:corona sun:coronal mass ejections(CMEs) sun:flares sun:filaments,prominences

Observational evidence of magnetic reconnection in a coronal bright point

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第9期20卷 171-182页

作者：宁宗军李东张擎旻 Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryNanjing 210033China

Magnetic reconnection is considered to be the fundamental process by which magnetic energy is converted into plasma or particle kinetic energy.Magnetic reconnection is a widely applied physics model to explain the solar eruption events,such as coronal bright points(CBPs).Meanwhile,it is an usual way of the solar physics research to look for the observational evidences of magnetic reconnection in the solar eruption events in order to support the model.In this paper,we have explored the evidences of magnetic reconnection in a CBP observed by the Atmospheric Imaging Assembly(AIA)onboard the Solar Dynamics Observatory(SDO)at NOAA No.11163 on 2011 March 5.Our observations show that this event is a small-scale loop system in active regions that have similar size as a traditional CBP and it might shed light on the physics of a traditional CBP.This CBP is bright in all nine AIA wavelengths and displays a flaring development with three bursts intermittently.Each burst exhibits a pair of bi-directional jets almost along a line.They originate from the same position(CBP core),then move in the opposite directions.Our findings are well consistent with the magnetic reconnection process by which the bi-directional plasma outflows are produced and radiate the bi-directional jets detected by SDO/AIA.These facts further support the conclusion that the CBP is produced by the magnetic reconnection process.

关键词： sun:UV radiation sun:corona sun:oscillation

Comparison of the coronal Green-line Intensities with the EUV Measurements from SDO/AIA

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第7期22卷 191-205页

作者： Xue-Fei Zhang Yu Liu Ming-Yu Zhao Ji-Hong Liu Abouazza Elmhamdi Teng-Fei Song Zi-Han Li Hong-Bo Li Fei-Yang Sha Jing-Xing Wang Xiao-Bo Li Yuan-Deng Shen Shun-Qing Liu Hong-Fei Liang R.M.Al-Shammari Yunnan Observatories Chinese Academy of SciencesKunming 650011China University of Chinese Academy of Sciences Beijing 100049China Shijiazhuang University Shijiazhuang 050035China School of Physical Science and Technology Southwest Jiaotong UniversityChengdu 610031China Department of Physics and Astronomy King Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia Yunnan Normal University School of Physics and Electronic InformationKunming 650500China Institute of Space Physics Luoyang Normal UniversityLuoyang 471934China

The intensity of the green line(Fe ⅩⅣ 5303 A) is the strongest in the visible spectrum of the solar corona,and this line has been used as long-term powerful diagnostic tools for studying the coronal configurations and hot plasma dynamics.However,it remains unclear and an open question whether there exists close relationship between the green line intensities and the coronal extreme ultraviolet(EUV) line emissions for various coronal structures.In this paper,we use the green-line data by the Lijiang YOGIS Lyot coronagraph and the EUV data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly instruments in order to perform direct comparisons and analyses,based on two algorithms developed to extract particular features in the low corona.It is found that,among the correlation coefficients obtained between the intensities of 5303 A and the EUV lines,the coefficients between the green line and the 211 A wavelength for different coronal structures and different limb locations always keep the highest values(ranging from 0.89 to 0.99),which has not been reported before.This result can be helpful and promising to link together the various physical processes involved at different heights in the corona by precisely tracking the bright loops or other features observed in 5303 A above the limb down to the correct surface locations revealed by the 211 A data.Furthermore,the ground-based observations of the coronal green line and the space-based EUV observations at 211 A can advantageously complement each other when there is a need.

关键词： sun:corona sun:magnetic fields stars:coronae

Recurrent coronal jets observed by SDO/AIA

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第10期21卷 213-220页

作者： Yan-Jie Zhang Qing-Min Zhang Jun Dai Zhe Xu Hai-Sheng Ji Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryCASNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China

In this paper,we carried out multiwavelength observations of three recurring jets on 2014November 7.The jets originated from the same region at the edge of AR 12205 and propagated along the same coronal loop.The eruptions were generated by magnetic reconnection,which is evidenced by continuous magnetic cancellation at the jet base.The projected initial velocity of jet2 is~402 km s^(-1).The accelerations in the ascending and descending phases of jet2 are not consistent,the former is considerably larger than the value of g_(⊙) at the solar surface,while the latter is lower than g_(⊙).There are two possible candidates of extra forces acting on jet2 during its propagation.One is the downward gas pressure from jet1when it falls back and meets with jet2.The other is the viscous drag from the surrounding plasma during the fast propagation of jet2.As a contrast,the accelerations of jet3 in the rising and falling phases are constant,implying that the propagation of jet3 is not significantly influenced by extra forces.

关键词： sun:corona sun:activity sun:magnetic fields