Solar Physics最新文献

{"title":"A New Solar Hard X-ray Image Reconstruction Algorithm for ASO-S/HXI Based on Deep Learning","authors":"Yuehan Xia,&nbsp;Yang Su,&nbsp;Hui Liu,&nbsp;Wenhui Yu,&nbsp;Zhentong Li,&nbsp;Wei Chen,&nbsp;Yu Huang,&nbsp;Weiqun Gan","doi":"10.1007/s11207-024-02399-4","DOIUrl":"10.1007/s11207-024-02399-4","url":null,"abstract":"<div><p>Most solar hard X-ray (HXR) imagers in the past and current solar missions obtain X-ray images via Fourier transform imaging technology, which requires proper imaging algorithms to reconstruct images from spatially-modulated or temporally-modulated signals. A variety of algorithms have been developed during the last 50 years for the characteristics of respective instruments. In this work, we present a new imaging algorithm developed based on deep learning for the Hard X-ray Imager (HXI) onboard the Advanced Space-based Solar Observatory (ASO-S) and the preliminary test results of the algorithm with both simulated data and observations. We first created a training dataset by obtaining modulation data from simulated HXR images of single, double and loop-shaped sources, respectively, and the patterns of HXI sub-collimators. Then, we introduced machine-learning algorithm to develop a pattern-based deep learning network model: HXI_DLA, which can directly produce an image from modulation counts. After training the model with simple sources, we tested DLA for simple sources, extended sources, and double sources for imaging dynamic range. Finally, we compared CLEAN and DLA images reconstructed from HXI observations of three flares. Overall, these imaging tests revealed that the current HXI_DLA method produces comparable image result to those from the widely used imaging method CLEAN. In some cases, DLA images are even slightly better. Besides, HXI_DLA is super fast for imaging and parameter-free. Although this is only the first step towards a fully developed and practical DLA method, the tests have shown the potential of deep learning in the field of solar hard X-ray imaging.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"299 11","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645684","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}

{"title":"Evaluation of Sunspot Areas Derived by Automated Sunspot-Detection Methods","authors":"Yoichiro Hanaoka","doi":"10.1007/s11207-024-02402-y","DOIUrl":"10.1007/s11207-024-02402-y","url":null,"abstract":"<div><p>Sunspot-area measurements using digital images captured by two telescopes at the Mitaka campus of the National Astronomical Observatory of Japan are conducted using automated sunspot detection. A comparison between sunspot areas derived from Mitaka and those from the reference data by Mandal et al. (<i>Astron. Astrophys.</i> <b>640,</b> A78, 2020), who compiled a crosscalibrated daily sunspot-area catalog, revealed that the correlation coefficients between them are high (0.96 – 0.97), whereas the areas in the Mitaka data are 70 – 83% of those of Mandal et al. The correlation is limited by the differences in observation times and detection capabilities of spots near the limb, with discrepancies in areas arising from different definitions of spot outlines. Given the high correlation and the ease of calibrating area discrepancies with a correction factor, automated sunspot detection appears promising for future sunspot-area measurements. Furthermore, we addressed the measurements of brightness deficit caused by sunspots.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"299 11","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636644","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}

{"title":"Calibration and Performance of the Full-Disk Vector MagnetoGraph (FMG) on Board the Advanced Space-Based Solar Observatory (ASO-S)","authors":"Xianyong Bai,&nbsp;Yuanyong Deng,&nbsp;Haiying Zhang,&nbsp;Jianfeng Yang,&nbsp;Fu Li,&nbsp;Jiangtao Su,&nbsp;Suo Liu,&nbsp;Yongliang Song,&nbsp;Kaifan Ji,&nbsp;Yu Huang,&nbsp;Xiao Yang,&nbsp;Dongguang Wang,&nbsp;Jiaben Lin,&nbsp;Junfeng Hou,&nbsp;Yingzi Sun,&nbsp;Wei Duan,&nbsp;Qian Song,&nbsp;Yang Bai,&nbsp;Xiaofan Wang,&nbsp;Haiqing Xu,&nbsp;Jie Chen,&nbsp;Ziyao Hu,&nbsp;Zhaoying Zheng,&nbsp;Houkun Ni,&nbsp;Yizhong Zeng,&nbsp;Zhen Wu,&nbsp;Jianing Wang,&nbsp;Wei Ge,&nbsp;Juan Lv,&nbsp;Lun Shen,&nbsp;Nange Wang,&nbsp;Jiawei He,&nbsp;Chenjie Wang","doi":"10.1007/s11207-024-02400-0","DOIUrl":"10.1007/s11207-024-02400-0","url":null,"abstract":"<div><p>We present the ground calibration and on-orbit performance of the Full-disk vector MagnetoGraph (FMG) payload on board the Advanced Space-Based Solar Observatory (ASO-S), which is China’s first spaceborne magnetograph. FMG has the ability to acquire the full-disk Stokes I, Q/I, U/I, and V/I maps with a spatial resolution of about 1.5 arcsec. The Lyot filter for the flight model has a full width at half maximum of 0.01 nm. Using two calibration lenses, we measure the non-uniform wavelength drift across the entire field of view, with a maximum value of 0.003 nm. The on-orbit polarization sensitivity is approximately 0.00039 and 0.0009 for the deep integration and routine modes, corresponding to a cadence of 18 and 2 minutes, respectively. The corresponding sensitivity of the longitudinal magnetic field is 8.5 G and 20 G with the current linear calibration coefficient of 21,913. Since 1 April 2023, FMG has released Level 2 filtergram and longitudinal magnetic field data products for active regions. Furthermore, line-of-sight Carrington synoptic magnetograms spanning a 27-day solar rotation can be generated, which have been released to the public since February 2024. The longitudinal magnetic field obtained by FMG is consistent with that of the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory and the Solar Magnetism and Activity Telescope at Huairou Solar Observing Station for the regions without magnetic saturation.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"299 11","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636643","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}

{"title":"Helioseismic Constraints: Past, Current, and Future Observations","authors":"Thierry Appourchaux","doi":"10.1007/s11207-024-02403-x","DOIUrl":"10.1007/s11207-024-02403-x","url":null,"abstract":"<div><p>I will review the history of the helioseismic observations since the beginning of the field. I will explain how each instrument was designed based upon the required observables, and to which modes these instruments are sensitive. The impact of these sensitivities on the rotation and structure inversion will be developed. I will conclude with what remains to be done in this field for the future of detection.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"299 11","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636924","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}

{"title":"Acoustic Waves in a High-Temperature Plasma II. Damping and Instability","authors":"B. B. Mikhalyaev,&nbsp;S. B. Derteev,&nbsp;N. K. Shividov,&nbsp;M. E. Sapraliev,&nbsp;D. B. Bembitov","doi":"10.1007/s11207-023-02196-5","DOIUrl":"10.1007/s11207-023-02196-5","url":null,"abstract":"<div><p>In this article we study the properties of acoustic waves in the rarefied high-temperature plasma of the solar corona, assuming that the heating and cooling of the plasma has a well-defined description. We consider a constant heating function supposing that the heating processes are generally established. For the radiative-loss function, a number of values are taken, which have been found using the CHIANTI code. On their basis, an analytical expression of the function in the form of a cubic interpolation has been worked out. We analyze the dispersion relation for linear acoustic waves. The heating and cooling function, introduced along with the classical expression of the thermal conductivity, allows us to obtain some specific results about their properties. In other words, a model of non-adiabatic acoustic waves with field-aligned thermal conduction, CHIANTI-based radiative cooling and constant heating function is constructed. Using the available observational data on compression waves, we can set the problem of finding the parameters of the coronal plasma. The model allows to specify the temperature range at which the thermal instability of waves is possible and to draw some conclusions about their damping. The coronal temperatures considered can be divided into intervals from 0.5 to 0.98 MK and from 4.57 to 8.38 MK, where the radiation function increases, and intervals from 0.98 to 4.57 MK and from 8.38 to 10 MK, where the radiation function decreases. With constant heating, at large wavelengths, acoustic waves can be unstable in the decreasing interval from 1.38 to 3.15 MK. In the increasing intervals, they may have a zero real part of the oscillation frequency and thus become non-propagating, also subject to a large wavelength. In some cases, the plasma density has a significant effect on the damping of acoustic oscillations due to heating and cooling. A change in density within the same order can lead to the fact that the heating and cooling effects prevail over the effect of thermal conductivity on long-wave perturbations.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 9","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02196-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4525174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"The Effect of Mass Flow on Slow MHD Oscillations of Curved Solar Coronal Loops","authors":"Igor Lopin","doi":"10.1007/s11207-023-02197-4","DOIUrl":"10.1007/s11207-023-02197-4","url":null,"abstract":"<div><p>Slow-mode standing waves are examined in the model of a bent magnetic slab with a plasma flow directed along curved magnetic field lines. The dispersion relation is obtained and studied both numerically and analytically regarding the principal slow mode. It is found that flow decreases the longitudinal oscillating motions and increases the radial kink-like motions, both produced by the principal slow mode. This feature may result in the development of Kelvin-Helmholtz instability when the flow speed exceeds the critical value, and this threshold depends on the azimuthal number <span>(m)</span>. When flow exists, a quasi-stationary wave structure that satisfies the footpoint boundary conditions has the form of a propagating wave modulated by a sinusoidal envelope. The corresponding eigenfrequencies of oscillations are found to decrease with increasing flow speed until <span>(u&lt; c_{Ti})</span>. The results obtained are used for seismological estimation of a plasma flow speed in coronal fan loops experiencing slow mode oscillations.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 9","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02197-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4526528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Helio-latitude Dependence of the Solar Wind Parameters and the Magneto-Gravitational Dragging of the Solar Wind","authors":"Babur M. Mirza","doi":"10.1007/s11207-023-02191-w","DOIUrl":"10.1007/s11207-023-02191-w","url":null,"abstract":"<div><p>A theoretical model of the magnetic-field coupling to the background gravitational field of a rotating Sun-like star is used here to calculate the solar-wind parameters dependence on the helio-latitude. In the measurements of the solar-wind parameters in <i>Ulysses</i>’ first full polar orbit (McComas et al.: <i>J. Geophys. Res.</i> <b>105</b>, 10419, 2000), the solar-wind parameters display a uniform behavior in the high-latitude regions compared with the slow variability in the low latitudes during solar minimum. Also the long-term variations in the solar-wind parameters reported in <i>Ulysses</i>’ second and third orbits (McComas et al.: <i>Geophys. Res. Lett.</i> <b>35</b>, L18103, 2008) are interpreted in terms of the magnetic-field variations during the solar cycle. The solar-wind acceleration due to the magneto-gravitational field around the Sun is shown to lead to mass flux and speed distribution as functions of the helio-latitude that exhibit the observed distinction between the solar-wind parameters in low and high latitudes. The calculated proton density, solar-wind temperature variation, and the momentum-flux profiles over the solar surface are found to be consistent with <i>Ulysses</i>’ first full-polar-orbit data.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4749083","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}

{"title":"Interpretable ML-Based Forecasting of CMEs Associated with Flares","authors":"Hemapriya Raju,&nbsp;Saurabh Das","doi":"10.1007/s11207-023-02187-6","DOIUrl":"10.1007/s11207-023-02187-6","url":null,"abstract":"<div><p>Coronal mass ejections (CMEs) that cause geomagnetic disturbances on the Earth can be found in conjunction with flares, filament eruptions, or independently. Though flares and CMEs are understood as triggered by the common physical process of magnetic reconnection, the degree of association is challenging to predict. From the vector magnetic field data captured by the <i>Helioseismic and Magnetic Imager</i> (HMI) onboard the <i>Solar Dynamics Observatory</i> (SDO), active regions are identified and tracked in what is known as Space Weather HMI Active Region Patches (SHARPs). Eighteen magnetic field features are derived from the SHARP data and fed as input for the machine-learning models to classify whether a flare will be accompanied by a CME (positive class) or not (negative class). Since the frequency of flare accompanied by CME occurrence is less than flare alone events, to address the class imbalance, we have explored the approaches such as undersampling the majority class, oversampling the minority class, and synthetic minority oversampling technique (SMOTE) on the training data. We compare the performance of eight machine-learning models, among which the Support Vector Machine (SVM) and Linear Discriminant Analysis (LDA) model perform best with True Skill Score (TSS) around 0.78?±?0.09 and 0.8?±?0.05, respectively. To improve the predictions, we attempt to incorporate the temporal information as an additional input parameter, resulting in LDA achieving an improved TSS of 0.92?±?0.04. We utilize the wrapper technique and permutation-based model interpretation methods to study the significant SHARP parameters responsible for the predictions made by SVM and LDA models. This study will help develop a real-time prediction of CME events and better understand the underlying physical processes behind the occurrence.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4369579","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}

{"title":"Turbulence in Sources of Decimetric Flare Continua","authors":"Marian Karlický","doi":"10.1007/s11207-023-02188-5","DOIUrl":"10.1007/s11207-023-02188-5","url":null,"abstract":"<div><p>Decimetric continua are commonly observed during long-lasting solar flares. Their frequency boundaries vary with time. We studied frequency boundary variations using the power spectrum analysis. Analyzing five decimetric continua, we found that their power spectra have a power-law form with the power-law index close to the Kolmogorov turbulence index ?5/3. The same power index was also found in the power spectra of radio flux variations at frequencies in the range of the frequency boundary variations. Moreover, these frequency boundary variations were highly correlated with the radio flux ones. We interpret these results to be due to turbulent density variations in the reconnection plasma outflow to the termination shock formed above flare loops. In three cases of decimetric continua, we estimated the level of the plasma density turbulence to be 7.6?–?11.2% of the mean plasma density. We think that the analysis of variations of decimetric continua can be used in studies of the plasma turbulence in solar flares.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02188-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4112462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Does the Time Resolution of the Geoeffective IMF Component Influence Its Annual, Semiannual and Diurnal Patterns?","authors":"Slaviša Živković,&nbsp;Giuliana Verbanac,&nbsp;Mario Bandić","doi":"10.1007/s11207-023-02184-9","DOIUrl":"10.1007/s11207-023-02184-9","url":null,"abstract":"<div><p>The geoeffective interplanetary magnetic field (IMF) component <span>(B_{mathrm{s}})</span>, <span>(B_{mathrm{s}} = B_{z, {mathrm{GSM}}})</span> when <span>(B_{z, {mathrm{GSM}}}&lt;0)</span>, is the most commonly used at 1-hour resolution for studying solar wind–magnetosphere coupling. In this way, the fluctuation of both <span>(B_{z,mathrm{GSM}})</span> (and thus <span>(B_{mathrm{s}})</span>) and IMF polarity within the hour are not taken into account. We investigate whether the global patterns of <span>(B_{mathrm{s}})</span> and <span>(B_{mathrm{s}})</span> sorted by IMF polarity (<span>(B_{mathrm{s}})</span> fields) change when these fluctuations are considered with respect to those based on hourly data. We have obtained <span>(B_{mathrm{s}})</span> fields at the high 16-second resolution. In this way, the information about the existence of <span>(B_{mathrm{s}})</span> fields within an hour is retained. The present study has shown that the initial resolution of the IMF data used to obtain <span>(B_{mathrm{s}})</span> fields (16-seconds or 1-hour) does not affect their characteristic patterns: diurnal, annual, and semiannual variations. Regardless of the initial IMF resolution, the <span>(B_{mathrm{s}})</span> sorted by the IMF polarity exists in all seasons. They show the two annual sinusoidal-like variations of opposite phase, the “pair of spectacles” pattern. The initial resolution affects only slightly the absolute values of <span>(B_{mathrm{s}})</span> fields. The results have shown that hourly values of IMF data are suitable for studying their global behavior within the year and also for investigating their relationship with magnetospheric quantities.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5007195","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}