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Extraction and analysis of Coronal High-temperature Components Based on Outlier Detection

Research in Astronomy and Astrophysics 2023年第6期23卷 143-152页

作者： Li-Yan Sun Kai-Fan Ji Jun-Chao Hong Hui Liu Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 101408China

The extraction of high-temperature regions in active regions(ARs)is an important means to help understand the mechanism of coronal *** important observational means of high-temperature radiation in ARs is the main emission line of Fe XVⅢin the 94?of the Atmospheric Imaging ***,the diagnostic algorithms for Fe XVⅢ,including the differential emission measure(DEM)and linear diagnostics proposed by Del based on the DEM,have been greatly limited for a long time,and the results obtained are different from the *** this paper,we use the outlier detection method to establish the nonlinear correlation between 94?and 171,193,211?based on the former researches by others.A neural network based on 171,193,211?is constructed to replace the low-temperature emission lines in the ARs of 94?.The predicted results are regarded as the low-temperature components of 94?,and then the predicted results are subtracted from 94?to obtain the outlier component of 94?,or Fe XVⅢ.Then,the outlier components obtained by neural network are compared with the Fe XVⅢobtained by DEM and Del's method,and a high similarity is found,which proves the reliability of neural network to obtain the high-temperature components of ARs,but there are still many *** order to analyze the differences between the Fe XVⅢobtained by the three methods,we subtract the Fe XVⅢobtained by the DEM and Del's method from the Fe XVⅢobtained by the neural network to obtain the residual value,and compare it with the results of Fe XIV in the temperature range of 6.1-6.45 *** is found that there is a great similarity,which also shows that the Fe XVⅢobtained by DEM and Del's method still has a large low-temperature component dominated by Fe XIV,and the Fe XVⅢobtained by neural network is relatively pure.

关键词： Sun:corona Sun:activity methods:statistical methods:data analysis techniques:image processing

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Testing the effect of solar wind parameters and geomagnetic storm indices on Galactic cosmic ray flux variation with automatically-selected Forbush decreases

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Research in Astronomy and Astrophysics 2021年第9期21卷 207-216页

作者： Jibrin Adejoh Alhassan Ogbonnaya Okike Augustine Ejikeme Chukwude Department of Physics and Astronomy University of NigeriaNsukka 400001Nigeria Department of Industrial Physics Ebonyi State UniversityAbakaliki 840001Nigeria

Forbush decrease(FD),discovered by Scott *** about 80 years ago,is referred to as the non-repetitive short-term depression in Galactic cosmic ray(GCR)flux,presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field(IMF).It is the most spectacular variability in the GCR intensity which appears to be the compass for investigators seeking solar-terrestrial *** method of selection and validation of FD events is very important to cosmic ray(CR)*** have deployed new computer software to determine the amplitude and timing of FDs from daily-averaged CR data at Oulu Neutron Monitor *** code selected 230 FDs between 1998 and *** an attempt to validate the new FD automated catalog,the relationship between the amplitude of FDs,and IMF,solar wind speed(SWS)and geomagnetic storm indices(Dst,kp,ap)is tested here.A two-dimensional regression analysis indicates significant linear relationship between large FDs(CR(%)≤-3)and solar wind data and geomagnetic storm indices in the present *** implications of the relationship among these parameters are discussed.

关键词： methods:data analysis methods:statistical Sun:coronal mass ejections(CMEs) (Sun:)solar-terrestrial relations (Sun:)solar wind (ISM:)cosmic rays

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Statefinder diagnostic and constraints on the Palatini f(R) gravity theories

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Research in Astronomy and Astrophysics 2018年第3期18卷 11-26页

作者： Shu-Lei Cao Song Li Hao-Ran Yu Tong-Jie Zhang Department of Astronomy Beijing Normal University Department of Physics Capital Normal University Tsung-Dao Lee Institute Shanghai Jiao Tong University School of Information Management School of Physics and Electric InformationShandong Provincial Key Laboratory of BiophysicsDezhou University

We focus on a series of f(R) gravity theories in Palatini formalism to investigate the probabilities of producing late-time acceleration for the flat Friedmann-Robertson-Walker(FRW) *** apply a statefinder diagnostic to these cosmological models for chosen series of parameters to see if they can be distinguished from one another. The diagnostic involves the statefinder pair{r,s},where r is derived from the scale factor a and its higher derivatives with respect to the cosmic time t,and s is expressed by r and the deceleration parameter q. In conclusion,we find that although two types of f(R) theories:(i) f(R) = R + αR~m-βR-nand(ii) f(R) = R + α lnR-β can lead to late-time acceleration,their evolutionary trajectories in the r-s and r-q planes reveal different evolutionary properties,which certainly justify the merits of the statefinder diagnostic. Additionally,we utilize the observational Hubble parameter data(OHD) to constrain these models of f(R) gravity. As a result,except for m = n = 1/2 in case(i),α = 0 in case(i) and case(ii) allow the ΛCDM model to exist in the 1σ confidence region. After applying the statefinder diagnostic to the best-fit models,we find that all the best-fit models are capable of going through the deceleration/acceleration transition stage with a late-time acceleration epoch,and all these models turn to the de Sitter point({r,s}={1,0}) in the future. Also,the evolutionary differences between these models are distinct,especially in the r-s plane,which makes the statefinder diagnostic more reliable in discriminating cosmological models.

关键词： dark energy cosmology:miscellaneous methods:data analysis

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A method to obtain the wind field characteristics of super-large aperture radio telescope site based on single-point wind tower and numerical simulation

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Research in Astronomy and Astrophysics 2020年第12期20卷 270-278页

作者： Fei-Long He Qian Xu Na Wang Chun-Hua Zhu School of Physics and Technology Xinjiang UniversityUrumqi 830046China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China

The influence of wind on the pointing accuracy of large aperture radio telescopes is becoming increasingly serious, especially at high observing frequency. Obtaining the wind field characteristics efficiently is very important to reduce the wind disturbance on antenna structure. In this paper, an error evaluation of numerical simulation method is established based on the measured data of single point wind tower, and the wind field characteristics are obtained from the evaluated numerical simulation results combined with the measured data for the 110 m aperture Qi Tai radio Telescope(QTT) site. According to the simulation results, compared with the measured data, the root mean square error(RMSE) of wind speed is less than 1 m s^-1, and the minimum wind speed RMSE is 0.2 m s^-1. An analysis of the wind field characteristics of the QTT site suggests that the active wind resistance design of the antenna periphery should focus on the SSW(south-south-west) direction.

关键词： telescopes site testing methods:data analysis

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Deconvolution with hybrid parameterizations for radio emission reconstruction

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Research in Astronomy and Astrophysics 2021年第4期21卷 287-296页

作者：张利 Long Xu Li-Gong Mi Ming Zhang Xiang Liu Feng Wang Yun-Jun Ruan Dan-Yang Li College of Big data and Information Engineering Guizhou UniversityGuiyang 550025China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China

Deconvolution is used to eliminate imperfections in the point spread function,such as sidelobes caused by incomplete sampling of radio telescopes,and is a key technology for radio synthesis *** telescopes have such high sensitivities that the observed celestial images may contain both compact and diffuse *** essentially requires deconvolution technology to have the ability to model *** this paper,a deconvolution algorithm based on hybrid parameterization is proposed for the rapid reconstruction of complex celestial *** this algorithm,scale-free parameterization is utilized to reconstruct compact emission,while multi-scale parameterization is employed to reconstruct diffuse *** data representing Square Kilometre Array(SKA)observations with realistic celestial brightness distributions are applied to test the performance of the *** experiments show that,compared with other state-of-the-art deconvolution algorithms,the algorithm proposed in this paper can reconstruct complex celestial structures well and provide competitive reconstruction results while greatly improving the reconstruction speed.

关键词： methods:data analysis techniques:image processing techniques:interferometric

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The influence of the observational strategies of pulsar timing on the properties of pulsar clocks

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Research in Astronomy and Astrophysics 2020年第12期20卷 323-329页

作者： Zhe-Hao Zhang Ming-Lei Tong Cheng-Shi Zhao Xing-Zhi Zhu Feng Gao National Time Service Center Chinese Academy of SciencesXi’an 710000China Key Laboratory of Time and Frequency Primary Standard Chinese Academy of SciencesXi’an 710600China University of Chinese Academy of Sciences Beijing 100049China Department of Applied Physics Xi’an University of Science and TechnologyXi’an 710054China

Pulsars are very stable spinning stars, which have the potential to application in the work of time-keeping and autonomous navigation in deep space. For time application, an individual pulsar can be regarded as a clock. The accuracy and stability of a pulsar clock are mainly determined by various timing noises and the measurement errors;however, they would be affected by the concrete observational *** four millisecond pulsars from the first data released by International Pulsar Timing Array(IPTA) as an example, we investigated the influences of different observational strategies on the properties of pulsar clocks by removing some data in various ways. We find that the long-term stabilities of pulsar clocks are nearly not affected by increasing the observational cadence with a fixed time span. It is also found that the capabilities of prediction by pulsar clocks are also hardly affected by different observational strategies,which is reflected by both the stable weighted root-mean-square(wrms) and the stability of the resulting pre-fit timing residuals, unless the data span is too short or the data period is too far from the start of prediction.

关键词： methods:data analysis time pulsars:general

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A GPU based single-pulse search pipeline(GSP)with database and its application to the Commensal Radio Astronomy FAST Survey(CRAFTS)

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Research in Astronomy and Astrophysics 2021年第12期21卷 488-498页

作者：游善平王培于徐红谢晓尧李菂刘志杰潘之辰岳友岭钱磊张彬陈宗浩 School of Computer Science and Technology Guizhou UniversityGuiyang 550025China Key Laboratory of Information and Computing Science Guizhou Province Guizhou Normal UniversityGuiyang 550001China CAS Key Laboratory of FAST NAOCChinese Academy of SciencesBeijing 100101China NAOC-UKZN Computational Astrophysics Centre University of Kwa Zulu-NatalDurban 4000South Africa

We developed a GPU based single-pulse search pipeline(GSP)with a candidate-archiving *** based upon the infrastructure of the open source PulsaR Exploration and Search Toolkit(PRESTO),GSP implements GPU acceleration of the de-dispersion and integrates a candidate-archiving *** applied GSP to the data streams from the Commensal Radio Astronomy FAST Survey(CRAFTS),which resulted in quasi-real-time *** integrated candidate database facilitates synergistic usage of multiple machine-learning tools and thus improves efficient identification of radio pulsars such as rotating radio transients(RRATs)and fast radio bursts(FRBs).We first tested GSP on pilot CRAFTS observations with the FAST Ultra-Wide Band(UWB)*** detected all pulsars known from the the Parkes multibeam pulsar survey in the corresponding sky area covered by the *** also discovered 13 new *** measured the computational efficiency of GSP to be~120 times faster than the original PRESTO and~60 times faster than an MPI-parallelized version of PRESTO.

关键词： methods:data analysis pulsars:general surveys:astronomical databases

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Propagating slow sausage waves in a sunspot observed by the New Vacuum Solar Telescope

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Research in Astronomy and Astrophysics 2020年第8期20卷 157-162页

作者： Song Feng Zheng Deng Ding Yuan Zhi Xu Xiao Yang Faculty of Information Engineering and Automation Kunming University of Science and TechnologyKunming 650500China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Institute of Space Science and Applied Technology Harbin Institute of TechnologyShenzhen 518055China Yunnan Observatories Chinese Academy of SciencesKunming 650011China

A sunspot is an ideal waveguide for a variety of magnetohydrodynamic waves,which carry a significant amount of energy to the upper atmosphere and could be used as a tool to probe the magnetic and thermal structure of a *** this study,we used the New Vacuum Solar Telescope and took highresolution image sequences simultaneously in both Ti O(7058±10?A)and Hα(6562±2.5?A)*** extracted the area and total emission intensity variations of sunspot umbra and analyzed the signals with synchrosqueezing *** found that the area and emission intensity varied with both three and five minute ***,the area and intensity oscillated in phase with each other,this fact hold in both Ti O and Hα*** interpret this oscillatory signal as a propagating slow sausage *** propagation speed is estimated at about 8 km s^-*** infer that this sunspot's umbra could have temperature as low as 2800–3500 K.

关键词： Sun:sunspot Sun:oscillations magnetohydrodynamics(MHD) methods:data analysis

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Pulsar timing observations with Haoping Radio Telescope

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Research in Astronomy and Astrophysics 2020年第7期20卷 187-192页

作者： Jin-Tao Luo Yu-Ping Gao Ting-Gao Yang Cheng-Shi Zhao Ming-Lei Tong Yong-Nan Rao Yi-Feng Li Bian Li Xing-Zhi Zhu Hai-Hua Qiao Xiao-Chun Lu National Time Service Center Chinese Academy of SciencesXi’an 710600China Key Lab of Precision Navigation&Timing Technology Chinese Academy of SciencesXi’an 710600China University of Chinese Academy of Sciences Beijing 100049China

We report pulsar timing observations carried out in L-band with NTSC’s 40-meter Haoping Radio Telescope(HRT),which was constructed in *** observations were carried out using the pulsar machine we *** observations toward millisecond pulsar J0437–4715 obtain a timing residual(r.m.s.)of 397 ns in the time span of 284 *** observations successfully detected Crab pulsar’s glitch that happened on 2019 July 23.

关键词： radio telescopes instrumentation:miscellaneous methods:data analysis pulsars:general

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Radio frequency interference detection based on the AC-UNet model

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Research in Astronomy and Astrophysics 2021年第5期21卷 168-178页

作者： Rui-Qing Yan Cong Dai Wei Liu Ji-Xia Li Si-Ying Chen Xian-Chuan Yu Shi-Fan Zuo Xue-Lei Chen College of Information Science and Technology Beijing Normal UniversityBeijing 100875China National Laboratory of Pattern Recognition Institute of AutomationChinese Academy of SciencesBeijing 100190China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Radio frequency interference(RFI)is a serious issue in radio *** paper proposes a U-Net network model with atrous convolution to detect *** the ability of convolutional neural networks to extract image features of RFI,and learning RFI distribution patterns,the detection model of the RFI is *** use observational data containing real RFIs obtained by the Tianlai telescope to train the model so that the model can detect *** the probability of a data point being RFI pixel by pixel,and set a *** the same time the dropout layer was added to avoid overfitting *** the predicted probability of a data point exceeds the threshold,it is considered that there is RFI,and if the predicted probability of a data point does not exceed the threshold,then it is considered that there is no RFI,so that the part of the image with RFI is *** results show that this approach can achieve satisfactory accuracy in the detection of radio observation images with a small amount of RFI.

关键词： methods:data analysis techniques:image processing methods:observational

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