Solar Physics最新文献

{"title":"Cyclical Behaviors of Sunspot-Group Tilt Angles in Solar Cycles 21 – 23","authors":"Peng-Xin Gao","doi":"10.1007/s11207-023-02117-6","DOIUrl":"10.1007/s11207-023-02117-6","url":null,"abstract":"<div><p>Based on the Debrecen Photoheliographic Data (DPD) sunspot catalog, we investigate the cyclical behaviors of tilt angles of all sunspot groups (SGs) and SGs with angular separation constraint <span>(S &gt; 2.5^{circ})</span> in Solar Cycles (SCs) 21 – 23. It is found that, the cyclical behaviors of tilt angles during SC 23 are different from those of SCs 21 and 22, confirmed by using the SDD sunspot catalog where possible, which are embodied in the following five aspects: (i) For all SGs (SGs with separation constraint), the percentage of SGs with larger absolute values of tilt angles in the declining phase than during the maximum phase is about 80% (60%) in SCs 21 and 22. In SC 23, the percentage of SGs with larger absolute values of tilt angles during the declining phase is about 1.10 times (at least not lower than) that during the maximum. (ii) During SCs 21 – 23, the yearly mean of tilt angles decreases with time for all SGs (SGs with separation constraint) and the slopes of the linear regression lines are negative: −0.404, −0.910, and −0.740/−1.005 (−0.500, −1.138, and −0.764/−0.576). (iii) During SCs 21 and 22, the yearly mean of the absolute value of tilt angles generally decreases with time for all SGs (SGs with separation constraint) and the slopes of the linear regression lines also are negative: −0.347 and −0.451 (−0.504 and −0.397). (iv) During SC 23, for all SGs, the yearly mean of the absolute value of tilt angles generally increases with time and the slope of the linear regression line is positive: 0.281/0.429. For SGs with separation constraint, the linear regression line to the yearly mean of the absolute value of tilt angles is almost horizontal and its slope is −0.008/0.014. (v) The yearly mean of latitude of SGs decreases steadily with time during each SC.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4535932","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":"Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24","authors":"Munetoshi Tokumaru,&nbsp;Ken’ichi Fujiki,&nbsp;Kazumasa Iwai","doi":"10.1007/s11207-023-02116-7","DOIUrl":"10.1007/s11207-023-02116-7","url":null,"abstract":"<div><p>Interplanetary scintillation (IPS) analysis is an effective technique for remotely sensing solar-wind disturbances, such as stream-interaction regions (SIRs) and coronal mass ejections (CMEs), which are the main drivers of space weather. Here, we employed 327-MHz IPS observations conducted at the Institute of Space–Earth Environmental Research, Nagoya University for the period of 1997 – 2019 to determine IPS indices that represent the density-fluctuation level of the inner heliosphere. We then compared these indices with the solar-wind density and speed measured near the Earth. Consequently, we found weak but significant positive correlations between the IPS indices and both the solar-wind density and speed gradient at a time lag of 0 days. This suggests that an increase in IPS indices corresponds to the arrival of the compression region associated with SIR or CME at the Earth, which is consistent with model calculations. Significant negative correlations were observed between the IPS and disturbance storm time (Dst) indices at a time lag of a few days; however, the correlations were too weak to enable reliable predictions of space weather. Possible reasons for these weak correlations are also discussed. Using the IPS indices, we determined the solar-cycle variation in the occurrence rate of solar-wind disturbances for the analysis period. The occurrence rates exhibited two maxima corresponding to the solar maximum and minimum, which are generally consistent with the combined effects of CME and SIR. The lower occurrence rates in Cycle 24 than in Cycle 23 reflect a weaker solar activity. These results suggest that the proposed IPS indices are useful for studying the long-term characteristics of solar-wind disturbances.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4535158","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":"Analysis of Front Side Halo CMEs and Their Solar Source Active Region and Flare Ribbon Properties","authors":"P. Vijayalakshmi,&nbsp;A. Shanmugaraju,&nbsp;M. Bendict Lawrance,&nbsp;Y.-J. Moon,&nbsp;Hyeonock Na,&nbsp;E. Ebenezer","doi":"10.1007/s11207-023-02113-w","DOIUrl":"10.1007/s11207-023-02113-w","url":null,"abstract":"<div><p>Halo coronal mass ejections (CMEs) from the Sun are the subset of CMEs, which are more energetic than the normal CMEs. Only the more energetic CMEs are observable in white-light coronagraphs when they are traveling along the line of sight (LOS) and a CME is better observed when it is traveling perpendicularly to the LOS. We investigated the flare associated front side halo CMEs, their active regions (ARs) and flare ribbon properties observed during the period of 2010 – 2016 in Solar Cycle 24. The aim of this study is to investigate the statistical relationship between the kinematic properties of CMEs and their source active region and flare ribbon properties. The properties of the solar source region (sunspot classification according to Hale and McIntosh, sunspot area, and the number of spots) and flare ribbons (total unsigned magnetic flux, total unsigned reconnection flux, active region area, and ribbon area) are obtained for the selected events and analyzed to find the dependence of the halo CME properties (linear speed, kinetic energy, space speed, and mass) on the source region characteristics. From the preliminary analysis, 13% of halo CMEs are found to be associated with X-class flares, 52% with M-class flares, and 35% with C-class flares. It is found that many events (45/60) were produced by <span>(upbeta upgamma updelta )</span> and <span>(upbeta upgamma )</span> Hale-type sunspot groups and Ekc/Dkc/Fkc McIntosh sunspot classes, which implies a degree of complexity of the involved sunspots. We found moderate correlations between the active region properties and CME properties, but strong correlation between the flare ribbons and CME properties. This result indicates that the kinematics of CMEs are determined by the role of magnetic reconnection and the flux related to it. We estimated the synthetic CME mass (using a synthetic CME generated based on a full ice-cream cone structure proposed recently by Na et al., <i>Astrophys. J.</i> <b>906</b>, 46, 2021). It is demonstrated that the estimated mass of halo CMEs is 1.44 times (without occulted area) and 2 times (with occulted area) that of the observed CME mass. Further, the relations between the halo CME synthetic mass with the active region and flare ribbon properties have been obtained.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02113-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4297716","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":"A New Global Nonlinear Force-Free Coronal Magnetic-Field Extrapolation Code Implemented on a Yin–Yang Grid","authors":"Argyrios Koumtzis,&nbsp;Thomas Wiegelmann","doi":"10.1007/s11207-023-02109-6","DOIUrl":"10.1007/s11207-023-02109-6","url":null,"abstract":"<div><p>The solar magnetic field dominates and structures the solar coronal plasma. Detailed insights into the coronal magnetic field are important to understand most physical phenomena there. While direct, routine measurements of the coronal magnetic field are not available, field extrapolation of the photospheric vector-field measurements into the corona is the only way to study the structure and dynamics of the coronal field. Here we focus on global coronal structures traditionally modeled using spherical grids and synoptic vector magnetograms as boundary conditions. We developed a new code that performs nonlinear force-free magnetic-field extrapolations in spherical geometry. Our new implementation is based on a well-established optimization principle on a Cartesian grid and a single spherical finite-difference grid. In the present work, for the first time, the algorithm is able to reconstruct the magnetic field in the entire corona, including the polar regions. The finite-difference numerical scheme that was employed in previous spherical-code versions suffered from numerical inefficiencies because of the convergence of those grids on the poles. In our new code, we implement the so-called Yin–Yang overhead grid, the structure of which addresses this difficulty. Consequently, both the speed and accuracy of the optimization algorithm are improved compared to the previous implementations. We tested our new code using the well known semi-analytical model (Low and Lou solution). This is a commonly used benchmark for nonlinear force-free extrapolation codes.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02109-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4617198","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 Irradiance Spectra from the Compact SOLSTICE (CSOL) Experiment: Instrument Design, FUV Calibration, Measurements, and Comparison of the 2018 Rocket Flight","authors":"Edward Thiemann,&nbsp;Jerald Harder,&nbsp;Thomas Woods,&nbsp;Martin Snow,&nbsp;Michael Klapetzky,&nbsp;Matthew Triplett,&nbsp;Alan Sims,&nbsp;Steven Penton,&nbsp;Mitchell Furst","doi":"10.1007/s11207-023-02107-8","DOIUrl":"10.1007/s11207-023-02107-8","url":null,"abstract":"<div><p>The <i>Compact SOLSTICE</i>, a compact far and mid ultraviolet (FUV and MUV) spectrograph, flew on a sounding rocket on 18 June 2018 to validate and potentially calibrate the <i>SOLar STellar Irradiance Comparison Experiment</i> (SOLSTICE) onboard the <i>Solar Radiation Climate Experiment</i> (SORCE) spacecraft. This article reports the instrument design, the calibration of the FUV channel, and the FUV irradiance measurements. Irradiance measurements are compared to SOLSTICE showing agreement within the combined instrumental uncertainties at most wavelengths, including the H Lyman-<span>(alpha )</span> emission at 121.6 nm. Some unexplained differences in line ratios between 130.5 nm and 147.5 nm are observed.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02107-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4081386","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":"Explosive Events in the Quiet Sun Near and Beyond the Solar Limb Observed with the Interface Region Imaging Spectrograph (IRIS)","authors":"C. E. Alissandrakis,&nbsp;J.-C. Vial","doi":"10.1007/s11207-023-02111-y","DOIUrl":"10.1007/s11207-023-02111-y","url":null,"abstract":"<div><p>We study point-like explosive events (EE), characterized by emission in the far wings of spectral lines, in a quiet region near the South Pole, using <i>Interface Region Imaging Spectrograph</i> (IRIS) spectra at two slit positions, slit-jaw (SJ) observations, and <i>Atmospheric Imaging Assembly</i> (AIA) images. The events were best visible in Si <span>iv</span> spectra; they were weak in SJs, occasionally visible in 1600 Å and 304 Å AIA images, and invisible in higher temperature AIA images. We identified EEs from position–time images in the far wings of the Si <span>iv</span> lines and measured their distance from the limb. A Gaussian model of the height distribution showed that EEs occur in a narrow (0.9^′′) height range, centered at 3.2^′′ above the continuum limb at 2832.0 Å. On the disk, we found that they occur in network boundaries. Further, we studied the line profiles of two bright EEs above the limb and one on the disk. We found that what appears as broad-band emission is actually a superposition of 2 – 3 narrow-band Gaussian components with well-separated line profiles, indicating that material is expelled towards and/or away from the observer in discrete episodes in time and in space. The expelled plasma accelerates quickly, reaching line-of-sight (LOS) velocities up to 90 km s⁻¹. Overall, the motion was practically along the LOS, as the velocity on the plane of the sky was small. In some cases, tilted spectra were observed that could be interpreted in terms of rotating motions of up to 30 km s⁻¹. We did not find any strong absorption features in the wing of the Si <span>iv</span> lines, although in one case, a very weak absorption feature was detected. No motions indicative of jets were detected in SJ or AIA images. Reconnection in an asymmetric magnetic-field geometry, in the middle or near the top of small loops, is a plausible explanation of their observational characteristics.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02111-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4425817","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 Solar Ultra-Violet Imaging Telescope (SUIT) Onboard Intelligence for Flare Observations","authors":"Manoj Varma,&nbsp;Sreejith Padinhatteri,&nbsp;Sakya Sinha,&nbsp;Anurag Tyagi,&nbsp;Mahesh Burse,&nbsp;Reena Yadav,&nbsp;Ghanshyam Kumar,&nbsp;Anamparambu Ramaprakash,&nbsp;Durgesh Tripathi,&nbsp;K. Sankarasubramanian,&nbsp;Krishnappa Nagaraju,&nbsp;Koushal Vadodariya,&nbsp;Srikar Tadepalli,&nbsp;Rushikesh Deogaonkar,&nbsp;Manjunath Olekar,&nbsp;Mohamed Azaruddin,&nbsp;Amrita Unnikrishnan","doi":"10.1007/s11207-023-02108-7","DOIUrl":"10.1007/s11207-023-02108-7","url":null,"abstract":"<div><p><i>Aditya</i>-L1 is India’s first observatory-class solar space mission to study the Sun from the Lagrange L₁ point. The <i>Solar Ultra-Violet Imaging Telescope</i> (SUIT) is one of the payloads onboard <i>Aditya</i>-L1. SUIT is an off-axis Ritchey–Chrétien (RC) telescope, which images the Sun onto a 4k×4k CCD covering a field-of-view of 1.5 R_⊙ with a plate scale of <span>(0.7'')</span> pixel⁻¹. One of the primary objectives of SUIT is to study the early evolution of solar flares with high temporal cadence in the near-UV wavelengths (200 – 400 nm). The SUIT onboard intelligence was developed to achieve this objective. The complete intelligence algorithm is divided into several sub-modules, each working on a specific aspect of intelligence. These are: the HEL1OS flare-trigger module: generates flare trigger using HEL1OS hard X-ray data, the flare-localization module: locates the flare on the SUIT full-disc images, the Region of Interest (RoI) tracking module: accounts for the shift in RoI coordinates caused by rotation of the Sun, auto-exposure control module: adjusts the exposure time depending upon the flare intensity for better contrast. In this article, these onboard-intelligence modules are explained in detail. The working principles of these modules are tested using available data from various existing missions and also using synthetic data, and the obtained results are presented. The modules are implemented in hardware using an Actel RTAX 2000S FPGA and are tested using a laboratory setup. From the testing, it is found that flares are successfully localized in a mean time of 40 seconds from the GOES soft X-ray catalog start time. Also, a temporal cadence of under three seconds for a single-filter flare RoI image is achieved.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-023-02108-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5173369","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":"Image Quality Specification for Solar Telescopes","authors":"Saraswathi Kalyani Subramanian,&nbsp;Sridharan Rengaswamy","doi":"10.1007/s11207-022-02105-2","DOIUrl":"10.1007/s11207-022-02105-2","url":null,"abstract":"<div><p>Modern large ground-based solar telescopes are invariably equipped with adaptive optics systems to enhance the high angular resolution imaging and spectroscopic capabilities in the presence of Earth’s atmospheric turbulence. The quality of the images obtained from these telescopes cannot be quantified with the Strehl ratio or other metrics that are used for nighttime astronomical telescopes directly. In this paper, we propose to use the root mean square (rms) granulation contrast as a metric to quantify the image quality of ground-based solar telescopes. We obtain semi-logarithmic plots indicating the correspondence between the Strehl ratio and the rms granulation contrast, for most practical values of the telescope diameters (<span>(D)</span>) and the atmospheric coherence diameters (<span>(r_{0})</span>), for various levels of adaptive optics compensation. We estimate the efficiency of a few working solar adaptive optics systems by comparing the results of our simulations with the Strehl ratio and rms granulation contrast published by these systems. Our results can be used in conjunction with a plausible 50% system efficiency to predict the lower bound on the rms granulation contrast expected from ground-based solar telescopes.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5039384","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":"Editorial Appreciation","authors":"Iñigo Arregui,&nbsp;John Leibacher,&nbsp;Cristina H. Mandrini,&nbsp;Lidia van Driel-Gesztelyi","doi":"10.1007/s11207-023-02110-z","DOIUrl":"10.1007/s11207-023-02110-z","url":null,"abstract":"","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5002550","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":"How Hot Can Small Solar Flares Get?","authors":"Louise Harra,&nbsp;Andrea F. Battaglia,&nbsp;Krzysztof Barczynski,&nbsp;Hannah Collier,&nbsp;Säm Krucker,&nbsp;Katharine K. Reeves,&nbsp;George Doschek","doi":"10.1007/s11207-022-02106-1","DOIUrl":"10.1007/s11207-022-02106-1","url":null,"abstract":"<div><p>The temperature reached by solar flares is a key parameter to understanding the physical process that causes the energy release. In this work, we analysed data from a Hinode Observing Programme that focused on high cadence measurement of the flaring plasma. This was carried out when the X-ray imager and spectrometer (STIX) on Solar Orbiter was observing. We analysed 3 small microflares, and determined their evolution and temperature. The temperature of the B2.8 microflare reached 16 MK. There was evidence in the smaller B1.4 flare of Fe <span>xxiv</span> emission, indicating that hot plasma of 15 MK can be reached.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"298 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-022-02106-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5001783","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}