Solar Physics最新文献

{"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":"Prediction of the Maximum Amplitude of Solar Cycle 25 Using the Ascending Inflection Point","authors":"A. J. P. Aparicio,&nbsp;V. M. S. Carrasco,&nbsp;J. M. Vaquero","doi":"10.1007/s11207-023-02194-7","DOIUrl":"10.1007/s11207-023-02194-7","url":null,"abstract":"<div><p>In this work, we predict the maximum amplitude (using the 13-month smoothed Solar Influences Data Analysis Center (SILSO) Sunspot Number, version 2) of Solar Cycle 25 using as a predictor the slope of the inflection point during the ascending part of the cycle. After a description of the data and methodology employed in this work, we obtain a value of 131 ± 32 for the maximum amplitude of Solar Cycle 25. Finally, we discuss this result in the context of the current debate on the prediction of solar activity and compare it with other predictions of Solar Cycle 25 obtained by other methods.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02194-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47258877","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":"Solar Soft X-Ray Irradiance Variability, II: Temperature Variations of Coronal X-Ray Features","authors":"H. N. Adithya,&nbsp;Rangaiah Kariyappa,&nbsp;Kanya Kusano,&nbsp;Satoshi Masuda,&nbsp;Shinsuke Imada,&nbsp;Joe Zender,&nbsp;Luc Damé,&nbsp;Hegde Manjunath,&nbsp;Edward DeLuca,&nbsp;Mark Weber","doi":"10.1007/s11207-023-02190-x","DOIUrl":"10.1007/s11207-023-02190-x","url":null,"abstract":"<div><p>The temperature variations of the corona and its individual surface features as a function of the solar cycle are an interesting and important aspect of understanding the physics of the Sun. To study the temperature variations, we have used the full-disk soft X-ray images of the corona obtained from Hinode/X-Ray Telescope (XRT) in different filters. A sophisticated algorithm has been developed in Python to segment the different coronal features such as the active regions (ARs), coronal holes (CHs), background regions (BGs), and X-ray bright points (XBPs), derived the total intensity of all the features, and generated the temperature maps of the corona using the filter ratio method. Due to the XRT straylight issue in some filters and unavailability of a good pair of images, we used for our analysis the filter combinations of Ti-poly and Al-mesh for the period from February 01, 2008 to May 08, 2012 and Al-poly and Al-mesh for the period from May 09, 2012 to June 30, 2021, in total for 14 years which covers Solar Cycle 24. The first analysis in using the XRT intensity values of the coronal features from segmented solar disk and their relation to solar activity is presented. We discuss the temperature variations of a full-disk corona and all features (ARs, CHs, BGs, and XBPs). Our time series plots of the average temperature of the full-disk and all the features show temperature fluctuations synchronized with the solar cycle (sunspot number). Although the temperature of all features varies, but the mean temperature estimated for the whole observed period of the full-disk is around 1.29 ± 0.16 MK and active regions (ARs) are around 1.76 ± 0.32 MK, whereas BGs, CHs, and XBPs are 1.27 ± 0.15 MK, 1.23 ± 0.14 MK, and 1.37 ± 0.18 MK, respectively. In addition, we found that the mean temperature contribution estimated of the background regions (BGs) is around 93.2%, whereas ARs, CHs, and XBPs are 3.1%, 1.6% and 2.1%, respectively, to the average coronal temperature of the full-disk. The temperature values and their variations of all the features suggest that the features show a high variability in their temperature and that the heating rate of the emission features may be highly variable on solar cycle timescales. It is evident from the analysis that the filter-ratio method can be directly used for temperature analysis of coronal features and to study their surface temperature variability as a function of solar magnetic activity.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46953233","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":"Stokes Inversion Techniques with Neural Networks: Analysis of Uncertainty in Parameter Estimation","authors":"Lukia Mistryukova,&nbsp;Andrey Plotnikov,&nbsp;Aleksandr Khizhik,&nbsp;Irina Knyazeva,&nbsp;Mikhail Hushchyn,&nbsp;Denis Derkach","doi":"10.1007/s11207-023-02189-4","DOIUrl":"10.1007/s11207-023-02189-4","url":null,"abstract":"<div><p>Magnetic fields are responsible for a multitude of solar phenomena, including potentially destructive events such as solar flares and coronal mass ejections, with the number of such events rising as we approach the peak of the 11-year solar cycle in approximately 2025. High-precision spectropolarimetric observations are necessary to understand the variability of the Sun. The field of quantitative inference of magnetic field vectors and related solar atmospheric parameters from such observations has been investigated for a long time. In recent years, very sophisticated codes for spectropolarimetric observations have been developed. Over the past two decades, neural networks have been shown to be a fast and accurate alternative to classic inversion methods. However, most of these codes can be used to obtain point estimates of the parameters, so ambiguities, degeneracies, and uncertainties of each parameter remain uncovered. In this paper, we provide end-to-end inversion codes based on the simple Milne-Eddington model of the stellar atmosphere and deep neural networks to both parameter estimation and their uncertainty intervals. The proposed framework is designed in such a way that it can be expanded and adapted to other atmospheric models or combinations of them. Additional information can also be incorporated directly into the model. It is demonstrated that the proposed architecture provides high accuracy results, including a reliable uncertainty estimation, even in the multidimensional case. The models are tested using simulations and real data samples.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41955272","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":"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}

{"title":"Lifetime of Sunspots and Pores","authors":"Andrey G. Tlatov","doi":"10.1007/s11207-023-02186-7","DOIUrl":"10.1007/s11207-023-02186-7","url":null,"abstract":"<div><p>The lifetime of individual sunspots and pores is analyzed according to <i>Solar Dynamics Observatory/Helioseismic and Magnetic Imager</i> (SDO/HMI) data from the period 2010 – 2022. It is found that the lifetime of individual sunspots and pores differs from the Gnevyshev–Waldmeier rule formulated for groups of sunspots. The dependence of the lifetime has a different pattern for different types of spots. For pores, the lifetime does not depend on the polarity of the magnetic field and has a logarithmic dependence on the area <span>(T_{mathrm{pr}}=0.24(pm 0.01)+0.55(pm 0.14) {mathrm{log}}(S_{mathrm{mx}}))</span>. For regular sunspots with a developed penumbra, the dependence on the area has a linear form, but depends on the polarity of the magnetic field. For sunspots with a magnetic field of the leading polarity <span>(T^{mathrm{sp}}_{mathrm{ld}} =-0.62 (pm 0.2)+0.036 (pm 0.002) S_{mathrm{mx}})</span>. For sunspots of trailing polarity <span>(T^{mathrm{sp}}_{mathrm{tr}} =0.95 (pm 0.1)+0.01 (pm 0.001) S_{mathrm{mx}})</span>. The decay time and the total lifetime of sunspots is related to the rate of flow in sunspots. The average vertical speed in sunspots decreases with their increasing area. Moreover, the flow rate in the sunspots of the trailing polarity is higher than in the sunspots of the leading polarity. This difference in the velocity explains the difference in the lifetime of the sunspots of the leading and trailing magnetic polarity.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4723030","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}