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  • Sunspot Records by Antonio Colla Just After the Dalton Minimum
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-11
    V. M. S. Carrasco, C. Bertolin, F. Domínguez-Castro, L. de Ferri, M. C. Gallego, J. M. Vaquero

    Antonio Colla was a meteorologist and astronomer who made sunspot observations at the Meteorological Observatory of the Parma University (Italy). He carried out his sunspot observations from 1830 to 1843, just after the Dalton Minimum. We have recovered 71 observation days for this observer. Unfortunately, many of these records are qualitative and we could only obtain the number of sunspot groups and/or

    更新日期:2020-08-11
  • Coronal Electron Density Fluctuations Inferred from Akatsuki Spacecraft Radio Observations
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-11
    D. Wexler, T. Imamura, A. Efimov, P. Song, L. Lukanina, H. Ando, E. Jensen, J. Vierinen, A. Coster

    Trans-coronal radio observations were taken during the 2011 observing campaign of the Akatsuki spacecraft through superior conjunction. The observed X-band (8.4 GHz) signals exhibit frequency fluctuations (FF) that are produced by temporal variations in electron density along the radio ray path. A two-component model for interpretation of the FF is proposed: FF scales largely with acoustic wave amplitude

    更新日期:2020-08-11
  • Comparative Study and Development of Two Contour-Based Image Segmentation Techniques for Coronal Hole Detection in Solar Images
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-07
    Sanmoy Bandyopadhyay, Saurabh Das, Abhirup Datta

    The study of solar coronal holes (CHs) is important in the understanding of solar physics and the prediction of space weather events, which have significant impact on space-based instruments, communication and navigation systems. With the availability of the multi-wavelength Atmospheric Imaging Assembly (AIA) instrument on board Solar Dynamics Observatory (SDO) satellite, a large volume of high-resolution

    更新日期:2020-08-08
  • A High-Efficiency and High-Accuracy Polarimeter for Solar Magnetic Field Measurements
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-06
    Deqing Ren, Zijian Han, Jing Guo

    Solar activity is dominated by the magnetic field. Nowadays, a polarimeter is a mandatory tool to measure solar magnetic fields, which are generally faint and correspond to a polarization of an order of \(10^{-2}\)–\(10^{-4}\). As such, polarization measurements of high efficiency with a high accuracy are crucial to investigate faint magnetic fields. Here we propose a high-efficiency and high-accuracy

    更新日期:2020-08-06
  • On the Expansion Speed of Coronal Mass Ejections: Implications for Self-Similar Evolution
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-04
    L. A. Balmaceda, A. Vourlidas, G. Stenborg, O. C. St. Cyr

    A proper characterization of the kinematics of coronal mass ejections (CMEs) is important not only for practical purposes, i.e. space weather forecasting, but also to improve our current understanding of the physics behind their evolution in the middle corona and into the heliosphere. The first and core step toward this goal is the estimation of the three main components of the CME speeds, namely the

    更新日期:2020-08-04
  • Dependence of Major Geomagnetic Storm Intensity ( Dst ≤ − 100 $\mathrm{Dst}\le -100$ nT) on Associated Solar Wind Parameters
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-04
    Gui-Ming Le, Gui-Ang Liu, Ming-Xian Zhao

    We investigate the influence of various solar wind parameters on the intensity of the associated major geomagnetic storm. SYM-Hmin was used to indicate the intensity of major geomagnetic storms, while \(I(B_{s})\), \(I(E_{y})\) and \(I(Q)\) were used to indicate the time integrals of the southward interplanetary magnetic field component (\(B_{s}\)), the solar wind electric field (\(E_{y}\)), and Q

    更新日期:2020-08-04
  • Magnetic and Velocity Field Topology in Active Regions of Descending Phase of Solar Cycle 23
    Sol. Phys. (IF 2.503) Pub Date : 2020-08-03
    R. A. Maurya, A. Ambastha

    We analyze the topology of photospheric magnetic fields and sub-photospheric flows of several active regions (ARs) that are observed during the peak to descending phase of Solar Cycle 23. Our analysis shows clear evidence of hemispheric preferences in all the topological parameters such as the magnetic, current and kinetic helicities, and the ‘curl-divergence’. We found that 68%(67%) ARs in the northern

    更新日期:2020-08-03
  • Identifying 8 mm Radio Brightenings During the Solar Activity Minimum
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-29
    Juha Kallunki, Merja Tornikoski, Irene Björklund

    Strong solar radio brightenings have been extensively studied in the past, and their correlation to the sunspots and active regions are already well known. But even when the Sun is ostensibly quiet, there is practically always some activity that can be detected in the radio domain. In this article we investigate these semi-active features at 8 mm using the radio telescope at Aalto University Metsähovi

    更新日期:2020-07-30
  • Editorial: Solar Wind at the Dawn of the Parker Solar Probe and Solar Orbiter Era
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-29
    Giovanni Lapenta, Andrei Zhukov, Lidia van Driel-Gesztelyi

    Solar Wind 15 brought together almost 250 experts from all continents of the world to discuss the current trends and future perspectives of the research on the Sun and its solar wind. The present article collection recaptures some of the highlights of their contributions.

    更新日期:2020-07-29
  • Evolution of Coronal Mass Ejections and the Corresponding Forbush Decreases: Modeling vs. Multi-Spacecraft Observations
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-29
    Mateja Dumbović, Bojan Vršnak, Jingnan Guo, Bernd Heber, Karin Dissauer, Fernando Carcaboso, Manuela Temmer, Astrid Veronig, Tatiana Podladchikova, Christian Möstl, Tanja Amerstorfer, Anamarija Kirin

    One of the very common in situ signatures of interplanetary coronal mass ejections (ICMEs), as well as other interplanetary transients, are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owes its specific morphology to the fact that the measuring instrument passed through the ICME head

    更新日期:2020-07-29
  • Investigation of the Middle Corona with SWAP and a Data-Driven Non-Potential Coronal Magnetic Field Model
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-27
    Karen A. Meyer, Duncan H. Mackay, Dana-Camelia Talpeanu, Lisa A. Upton, Matthew J. West

    The large field-of-view of the Sun Watcher using Active Pixel System detector and Image Processing (SWAP) instrument onboard the PRoject for Onboard Autonomy 2 (PROBA2) spacecraft provides a unique opportunity to study extended coronal structures observed in the EUV in conjunction with global coronal magnetic field simulations. A global non-potential magnetic field model is used to simulate the evolution

    更新日期:2020-07-27
  • Small Size Ground Level Enhancements During Solar Cycle 24
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-27
    Leonty I. Miroshnichenko, Chuan Li, Victor G. Yanke

    We continue the systematical empirical search for small size ground level enhancements (GLEs) (also called “hidden” or sub-GLEs) using data from ground-based instruments for Solar Cycle 24. The starting point of this research is the hypothesis that small size GLEs may be indicative of the acceleration of solar energetic particles (SEPs) by shocks driven by coronal mass ejections (CMEs). A crucial parameter

    更新日期:2020-07-27
  • Investigation of the Hemispheric Asymmetry in Solar Flare Index During Solar Cycle 21 – 24 from the Kandilli Observatory
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-23
    Soumya Roy, Amrita Prasad, Koushik Ghosh, Subhash Chandra Panja, Sankar Narayan Patra

    The hemispheric asymmetry of the solar-flare index during 1976 – 2018 from the Kandilli Observatory is studied in this investigation. The temporal duration covers Solar Cycles 21 – 23 and almost the whole of Solar Cycle 24. Different methodologies, such as cross-correlation analysis, rescaled-range analysis, empirical mode decomposition, and date-compensated discrete Fourier transform, have been used

    更新日期:2020-07-23
  • The Evolution over Time and North–South Asymmetry of Sunspots and Solar Plages for the Period 1910 to 1937 Using Data from Ebro Catalogues
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-23
    V. de Paula, J. J. Curto

    In this work, we analysed both the evolution over time and the north–south (N-S) asymmetry of certain solar features with regards to their morphological type and area. We examined and compared simultaneously 4212 photospheric sunspot groups and 5781 chromospheric solar plage groups using data from the Ebro Observatory catalogues for the period 1910–1937. We found that the most frequently recorded groups

    更新日期:2020-07-23
  • Forward Synthesis of Polarized Emission in Target DKIST Coronal Lines Applied to 3D MURaM Coronal Simulations
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-20
    Thomas Schad, Gabriel Dima

    Self-consistent magnetohydrodynamic simulations of the solar corona with fine (\(\lesssim10\) km) grid scales are now being realized in parallel to advancements in high-resolution coronal spectropolarimetry provided by the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). We investigate the synthesis of polarized emission in the presence of apparent coronal fine structure exhibited

    更新日期:2020-07-20
  • Self-consistent Nonlinear Force-Free Field Reconstruction from Weighted Boundary Conditions
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-17
    A. Mastrano, K. E. Yang, M. S. Wheatland

    Photospheric vector magnetogram data are often used as boundary conditions for force-free coronal magnetic field extrapolations. In general, however, vector magnetogram data are not consistent with the force-free assumption. In this article, we demonstrate a way to deal with inconsistent boundary data, by generalizing the “self-consistency procedure” of Wheatland and Régnier (Astrophys. J. Lett.700

    更新日期:2020-07-17
  • Magnetic Field, Electron Density and Their Spatial Scales in Zebra Pattern Radio Sources
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-15
    L. V. Yasnov, M. Karlický

    Zebra patterns (zebras) play an important role in the plasma diagnostics during solar flares. Considering their double plasma resonance (DPR) model, we present an improved method for the determination of the gyro-harmonic numbers of the zebra stripes that are essential in determining the electron density and magnetic field strength in zebra sources. Furthermore, we present the magnetic field and density

    更新日期:2020-07-16
  • Synoptic Measurements of Electron Temperature and Speed in the Solar Corona with Next Generation White-Light Coronagraph
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-15
    Nelson Reginald, Jeffrey Newmark, Lutz Rastaetter

    Current white-light coronagraphs measure polarized brightness (pB) of the solar corona using a single bandpass filter to measure the density of electrons. However, future coronagraphs can be modified to take pB images through four bandpass filters to measure density, temperature and speed of electrons. In this article, we use a spherical three dimensional coronal model of the Bastille Day coronal mass

    更新日期:2020-07-15
  • Solar Flare Forecasting Using Time Series and Extreme Gradient Boosting Ensembles
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-14
    T. Cinto, A. L. S. Gradvohl, G. P. Coelho, A. E. A. da Silva

    Space weather events may cause damage to several types of technologies, including aviation, satellites, oil and gas industries, and electrical systems, leading to economic and commercial losses. Solar flares belong to the most significant events, and refer to sudden radiation releases that can affect the Earth’s atmosphere within a few hours or minutes. Therefore, it is worth designing high-performance

    更新日期:2020-07-14
  • Multilevel Observations of the Oscillations in the First Active Region of the New Cycle
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-14
    A. A. Chelpanov, N. I. Kobanov

    For the first time, a multiwavelength investigation of the oscillation dynamics in a solar facula from its birth to decay was carried out. We performed spectral observations of active region NOAA 12744 at the Horizontal Solar Telescope of the Sayan Solar Observatory in the H\(\alpha \), He i 10830 Å, and Si i 10827 Å lines. We used Solar Dynamics Observatory (SDO) line-of-sight magnetic field data

    更新日期:2020-07-14
  • New Types of the Chromospheric Anemone Microflares: Case Study
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-13
    Yurii V. Dumin, Boris V. Somov

    Chromospheric anemone microflares (AMFs) are transient solar phenomena whose emission regions have a multi-ribbon configuration. As distinct from the so-called “atypical” solar flares, also possessing a few ribbons, the temporal and spatial scales of AMFs are a few times less, and the configuration of their ribbons is more specific (star-like). The previously reported AMFs had typically three or, less

    更新日期:2020-07-13
  • Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008 – 2014
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-09
    D. Maričić, B. Vršnak, A. M. Veronig, M. Dumbović, F. Šterc, D. Roša, M. Karlica, D. Hržina, I. Romštajn

    A sample of isolated Earth-impacting interplanetary coronal mass ejections (ICMEs) that occurred in the period January 2008 to August 2014 is analyzed to study in detail the ICME in situ signatures, with respect to the type of filament eruption related to the corresponding CME. Observations from different vantage points provided by the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial

    更新日期:2020-07-09
  • The STIX Aspect System (SAS): The Optical Aspect System of the Spectrometer/Telescope for Imaging X-Rays (STIX) on Solar Orbiter
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-03
    A. Warmuth, H. Önel, G. Mann, J. Rendtel, K. G. Strassmeier, C. Denker, G. J. Hurford, S. Krucker, J. Anderson, S.-M. Bauer, W. Bittner, F. Dionies, J. Paschke, D. Plüschke, D. P. Sablowski, F. Schuller, V. Senthamizh Pavai, M. Woche, D. Casadei, S. Kögl, N. G. Arnold, H.-P. Gröbelbauer, D. Schori, H. J. Wiehl, A. Csillaghy, O. Grimm, P. Orleanski, K. R. Skup, W. Bujwan, K. Rutkowski, K. Ber

    The Spectrometer/Telescope for Imaging X-rays (STIX) is a remote sensing instrument on Solar Orbiter that observes the hard X-ray bremsstrahlung emission of solar flares. This paper describes the STIX Aspect System (SAS), a subunit that measures the pointing of STIX relative to the Sun with a precision of \(\pm 4''\), which is required to accurately localize the reconstructed X-ray images on the Sun

    更新日期:2020-07-03
  • Coronal Photopolarimetry with the LASCO-C2 Coronagraph over 24 Years [1996 – 2019]
    Sol. Phys. (IF 2.503) Pub Date : 2020-07-01
    Philippe Lamy, Antoine Llebaria, Brice Boclet, Hugo Gilardy, Michael Burtin, Olivier Floyd

    We present an in-depth characterization of the polarimetric channel of the Large-Angle Spectrometric COronagraph/LASCO-C2 onboard the Solar and Heliospheric Observatory (SOHO). The polarimetric analysis of the white-light images makes use of polarized sequences composed of three images obtained though three polarizers oriented at \(+60^{\circ }\), \(0^{\circ }\), and \(-60^{\circ }\), complemented

    更新日期:2020-07-01
  • Nonaxisymmetric Component of Solar Activity: the Vector of the Longitudinal Asymmetry
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-30
    E. S. Vernova, M. I. Tyasto, D. G. Baranov, O. A. Danilova

    The vector representation of sunspots is used to study the nonaxisymmetric features of the solar activity distribution (sunspot data from Greenwich–USAF/NOAA, 1874–2016). Each sunspot is represented by a polar vector with modulus equal to the sunspot area and the phase equal to the sunspot heliolongitude. The vector sum of these individual vectors defines both the magnitude of the longitudinal asymmetry

    更新日期:2020-06-30
  • Observation of Differential Rotation Within a Sunspot Umbra During an X-Class Flare
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-30
    Richard Grimes, Balázs Pintér, Huw Morgan

    Sunspots and their dynamics dominate the magnetic topology and evolution of both the photosphere and the overlying coronal active regions. Thus a comprehensive understanding of their behaviour is essential to understanding the solar magnetic field. A new technique is presented for applying multiple ellipse fits as a method for rotation tracking of sunspot umbrae. The method is applied to a sunspot

    更新日期:2020-06-30
  • Randomness in Sunspot Number: A Clue to Predict Solar Cycle 25
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-30
    Bharati Kakad, Raj Kumar, Amar Kakad

    Forecasting of solar activity is extremely important, due to its impact on our space-based technology. In recent years, we have observed a continuous decline in the peak sunspot number for Solar Cycles (SCs) 21 to 24. We are more curious about peak activity of SC 25 because if the solar activity weakens further, then it may be an indication of new extended minima. So far, the daily sunspot-number data

    更新日期:2020-06-30
  • Validity of Nonlinear Force-Free Field Optimization Reconstruction
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-29
    G. V. Rudenko, I. S. Dmitrienko

    We evaluate the validity of Nonlinear Force Free Field (NLFFF) reconstruction performed with Optimization class (OPTI) codes. We present a postprocessing method that removes the inevitable non-solenoidality of the magnetic field calculated by OPTI codes, which is caused by the noticeable role played by the gradient of the gas pressure in the force balance at photospheric heights, and by some of the

    更新日期:2020-06-29
  • Long- and Short-Term Evolutions of Magnetic Field Fluctuations in High-Speed Streams
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-23
    Gilbert Pi, Alexander Pitňa, Zdenek Němeček, Jana Šafránková, Jih-Hong Shue, Ya-Hui Yang

    High-speed streams (HSSs) are believed to be only slightly affected by different interactions on their path from the Sun to Earth and thus the analysis of their observations can provide information on the structure and temporal variations of the magnetic field and plasma parameters at the source region. We have chosen three coronal holes supplying 14 HSSs recorded by Wind in 2008. For each HSS, we

    更新日期:2020-06-23
  • EMD and LSTM Hybrid Deep Learning Model for Predicting Sunspot Number Time Series with a Cyclic Pattern
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-22
    Taesam Lee

    The prediction of a time series such as climate indices and the sunspot number (SSN) with long-term oscillatory behaviors has been a challenging task due to the complex combination of oscillations. Frequency extraction algorithms have been developed to separate a time series into different oscillation components according to frequency, such as empirical model decomposition (EMD) and wavelet analysis

    更新日期:2020-06-23
  • Short-Term Periodicities Observed in Neutron Monitor Counting Rates
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-22
    A. López-Comazzi, J. J. Blanco

    Neutron monitor counting rates and solar wind velocity, interplanetary magnetic field, sunspot number and total solar irradiance measurements from 2013 to 2018 corresponding to the end of solar maximum and the decreasing phase of the Solar Cycle 24 have been used. The main objective is to check whether the periodicities observed in the cosmic rays are affected by the magnetic rigidity or the height

    更新日期:2020-06-23
  • Model Fitting of Wind Magnetic Clouds for the Period 2004 – 2006
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-22
    R. P. Lepping, C.-C. Wu, D. B. Berdichevsky, A. Szabo

    We give the results of parameter fitting of the magnetic clouds (MCs) observed by the Wind spacecraft for the three year period – 2004 to the end of 2006 (the “Present period”) using the force-free MC model of Lepping, Jones, and Burlaga (J. Geophys. Res.95, 11957, 1990). There were 19 MCs identified in the Present period, which was mainly in the declining phase of the solar cycle. The long-term occurrence

    更新日期:2020-06-23
  • Radio Sounding Measurements of the Solar Corona Using Giant Pulses of the Crab Pulsar in 2018
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-19
    Munetoshi Tokumaru, Kaito Tawara, Kazuhiro Takefuji, Mamoru Sekido, Toshio Terasawa

    Observations of the Crab pulsar at 327 MHz were made at the Toyokawa Observatory of the Institute for Space-Earth Environmental Research, during the solar occultation in mid-June 2018 to investigate the coronal plasma density in the weak sunspot cycle, Cycle 24. The dispersion measurements (DMs) were determined using giant pulses detected from observations of the Crab pulsar. The systematic increase

    更新日期:2020-06-19
  • A New Tool for Predicting the Solar Cycle: Correlation Between Flux Transport at the Equator and the Poles
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-18
    Susanta Kumar Bisoi, P. Janardhan

    Magnetic flux cancellation on the Sun plays a crucial role in determining the way in which the net magnetic flux changes in every solar cycle, affecting the large scale evolution of the coronal magnetic field and heliospheric environment. We have investigated the correlation between the solar magnetic flux cancelled at the equator and the solar magnetic flux transported to the poles by comparing the

    更新日期:2020-06-18
  • Recursive Integer Sequences, Detected in Solar-Cycle Periodicities Measured in Numbers of Rigid Rotations of the Sun
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-17
    Jean-Guillaume Richard

    Consecutive integers in the recursive number sequences, the Fibonacci sequence (Fn) and the Lucas sequence (Ln), are detected in the lengths of solar-activity variations from ≈ 1 yr to ≈ 12 yr, measured in rigid rotations of the Sun at the helioseismologically determined frequency in the radiative zone, \(433 \pm 3\) nHz. One rotation is denoted by the symbol \(\Omega \). Firstly, in the new international

    更新日期:2020-06-17
  • On the Emission Region of Type II Radio Bursts in Interplanetary Shock Fronts
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-16
    E. Aguilar-Rodriguez, P. Corona-Romero

    We analyze Type II radio emissions observed by the Radio and Plasma Waves instrument onboard Wind to determine the emission region in shock fronts, using the blast wave reconstruction technique. Our results suggest that the processes of emission of a Type II radio burst occur not only in the upstream region of the shock, i.e. the region that precedes the collision, but also that there must be an emission

    更新日期:2020-06-16
  • Thermodynamic Structure of the Solar Corona: Tomographic Reconstructions and MHD Modeling
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-10
    Diego G. Lloveras, Alberto M. Vásquez, Federico A. Nuevo, Cecilia Mac Cormack, Nishtha Sachdeva, Ward Manchester, Bartholomeus Van der Holst, Richard A. Frazin

    We carry out a study of the global three-dimensional (3D) structure of the electron density and temperature of the quiescent inner solar corona (\(r<1.25\,\mathrm{R_{\odot }}\)) by means of tomographic reconstructions and magnetohydrodynamic simulations. We use differential emission measure tomography (DEMT) and the Alfvén Wave Solar Model (AWSoM), in their latest versions. Two target rotations were

    更新日期:2020-06-10
  • Development of a Confined Circular-Cum-Parallel Ribbon Flare and Associated Pre-Flare Activity
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-08
    Pooja Devi, Bhuwan Joshi, Ramesh Chandra, Prabir K. Mitra, Astrid M. Veronig, Reetika Joshi

    We study a complex GOES M1.1 circular ribbon flare and related pre-flare activity on 26 January 2015 [SOL2015-01-26T16:53] in the solar active region NOAA 12268. This flare activity was observed by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The examination of photospheric magnetograms during

    更新日期:2020-06-08
  • On the Relationship Between the Transit Time of ICMEs and Strength of the Initiated Geomagnetic Storms
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-08
    I. M. Chertok

    More than 140 isolated non-recurrent geomagnetic storms (GMSs) of various intensities from extreme to weak are considered; these are reliably identified with solar eruptive sources (coronal mass ejections, CMEs). The analysis aims to obtain a possibly complete picture of the relationship between the transit time of propagation of CMEs and interplanetary coronal mass ejections (ICMEs) from the Sun to

    更新日期:2020-06-08
  • Inferring the Magnetic Field Asymmetry of Solar Flares from the Degree of Polarisation at Millimetre Wavelengths
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-04
    D. F. Silva, P. J. A. Simões, R. F. Hidalgo Ramírez, A. Válio

    Polarisation measurements of solar flares at millimetre-waves were used to investigate the magnetic field configuration of the emitting sources. We analyse two solar flares (SOL2013-02-17 and SOL2013-11-05) observed by the POlarisation Emission of Millimetre Activity at the Sun (POEMAS) at 45 and 90 GHz, at microwaves from 1 – 15 GHz by the Radio Solar Telescope Network (RSTN), and at high frequencies

    更新日期:2020-06-04
  • Recalculation of the Wolf Series from 1877 to 1893
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-02
    Thomas K. Friedli

    Homogeneity is considered as the most important property of the Wolf series of sunspot relative numbers, or Wolf numbers, since without a stable scale no valid conclusions about variations in the long-term progress of solar activity can be drawn. However, the homogeneity testing of the Wolf series is a difficult task, since the raw data entering the series and the methods of data-reduction and interpolation

    更新日期:2020-06-02
  • Deconstructing Sunlight – A Community Enterprise
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-02
    J. W. Harvey

    Good fortune allowed me to have a career in solar research. With the aid of many generous and gifted colleagues, I have tried to learn more about the Sun’s magnetic and velocity fields through observation and instrumentation development. These interests captured me early and remain strong. In this memoir I describe my path through 60 years of solar research that was sometimes random but did not deviate

    更新日期:2020-06-02
  • Sunspot Observations by Barnaba Oriani (1778 – 1779)
    Sol. Phys. (IF 2.503) Pub Date : 2020-06-02
    J. M. Nogales, V. M. S. Carrasco, R. Arlt, F. Domínguez-Castro, J. M. Vaquero

    We present the sunspot observations made by Barnaba Oriani in 1778 and 1779 at the Brera Observatory (Milan, Italy). We have computed the number of sunspot groups and individual sunspots and extracted the positions of all individual sunspots recorded by Oriani. It must be highlighted that the observations made by Oriani in 1779 are not included in the current sunspot-group number database. The observations

    更新日期:2020-06-02
  • Ring of Stations Method in Cosmic Rays Variations Research
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-29
    M. A. Abunina, A. V. Belov, E. A. Eroshenko, A. A. Abunin, V. G. Yanke, A. A. Melkumyan, N. S. Shlyk, I. I. Pryamushkina

    For over 60 years, neutron monitors have been the main standard and high precision detectors for measuring cosmic rays with energy from 400 MeV to hundreds GeV. In order to obtain sufficiently complete information about the distribution of cosmic rays outside the magnetosphere, it is necessary to have a network of detectors spaced evenly enough around the globe. The ring of stations method is one of

    更新日期:2020-05-29
  • Modeling the Time Delay Problem of Galactic Cosmic Ray Flux in Solar Cycles 21 and 23
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-25
    M. Siluszyk, K. Iskra

    We present a 2-dimensional time-dependent simulation based on Parker’s transport equation (PTE) describing the propagation of energetic astroparticles – cosmic rays (CR) in the heliosphere. PTE is a second order partial differential equation containing four major processes: diffusion, convection, drift, and adiabatic cooling responsible for modulation of the CR flux in the heliosphere. We implement

    更新日期:2020-05-25
  • The Hidden Cycle of the Solar Tesseral-Quadrupole Magnetic Field
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-22
    V. P. Mikhaylutsa

    Based on the Stanford harmonic coefficients of the solar magnetic fields and on the results of Shannon entropy transfer technique applied to magnetic mode intensities (Mikhaylutsa in J. Astrophys. Astron.40, 22, 2019), we have found that most of the medium and small-scale solar magnetic modes (order \(l > 3\); degree \(m > 0\)) must be interdependent. The features and physical sense of these dependencies

    更新日期:2020-05-22
  • Long-Term Evolution of the Solar Corona Using PROBA2 Data
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-20
    Marilena Mierla, Jan Janssens, Elke D’Huys, Laurence Wauters, Matthew J. West, Daniel B. Seaton, David Berghmans, Elena Podladchikova

    We use The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) imager onboard the Project for Onboard Autonomy 2 (PROBA2) mission to study the evolution of large-scale EUV structures in the solar corona observed throughout Solar Cycle 24 (from 2010 to 2019). We discuss the evolution of the on-disk coronal features and at different heights above the solar surface based on EUV intensity

    更新日期:2020-05-20
  • Magnetic Flux Emergence in a Coronal Hole
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-19
    Judith Palacios, Dominik Utz, Stefan Hofmeister, Kilian Krikova, Peter Gömöry, Christoph Kuckein, Carsten Denker, Meetu Verma, Sergio Javier González Manrique, Jose Iván Campos Rozo, Július Koza, Manuela Temmer, Astrid Veronig, Andrea Diercke, Ioannis Kontogiannis, Consuelo Cid

    A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (Hinode Observing Plan 338, 20 – 30 September 2017), the GREGOR solar telescope, and the Vacuum Tower Telescope (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24 September 2017, a very extended

    更新日期:2020-05-19
  • Forecasting Solar Cycle 25 Using Deep Neural Networks
    Sol. Phys. (IF 2.503) Pub Date : 2020-05-19
    B. Benson, W. D. Pan, A. Prasad, G. A. Gary, Q. Hu

    With recent advances in the field of machine learning, the use of deep neural networks for time series forecasting has become more prevalent. The quasi-periodic nature of the solar cycle makes it a good candidate for applying time series forecasting methods. We employ a combination of WaveNet and Long Short-Term Memory neural networks to forecast the sunspot number using the years 1749 to 2019 and

    更新日期:2020-05-19
  • Simulating White-Light Images of Coronal Structures for Parker Solar Probe/WISPR: Study of the Total Brightness Profiles
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-29
    Giuseppe Nisticò, Volker Bothmer, Angelos Vourlidas, Paulett C. Liewer, Arnaud F. Thernisien, Guillermo Stenborg, Russell A. Howard

    The Wide-field Imager for Parker Solar Probe (WISPR) captures unprecedented white-light images of the solar corona and inner heliosphere. Thanks to the uniqueness of the Parker Solar Probe’s (PSP) orbit, WISPR is able to image “locally” coronal structures at high spatial and time resolutions. The observed plane of sky, however, rapidly changes because of the PSP’s high orbital speed. Therefore, the

    更新日期:2020-04-29
  • Relationships between Interplanetary Coronal Mass Ejection Characteristics and Geoeffectiveness in the Declining Phase of Solar Cycles 23 and 24
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-24
    M. Bendict Lawrance, Y.-J. Moon, A. Shanmugaraju

    In this paper, we have examined the relationships between the characteristics of interplanetary coronal mass ejections (ICMEs) and geoeffectiveness in the declining phase of Solar Cycles 23 and 24. We discuss the results in comparison with those of the rising phase. Major results of this study are as follows: The ICMEs in the declining phase of Cycle 23 have generated higher storm strength than those

    更新日期:2020-04-24
  • ICME Evolution in the Inner Heliosphere
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-23
    J. G. Luhmann, N. Gopalswamy, L. K. Jian, N. Lugaz

    ICMEs (interplanetary coronal mass ejections), the heliospheric counterparts of what is observed with coronagraphs at the Sun as CMEs, have been the subject of intense interest since their close association with geomagnetic storms was established in the 1980s. These major interplanetary plasma and magnetic field transients, often preceded and accompanied by solar energetic particles (SEPs), interact

    更新日期:2020-04-23
  • Formation of Two Homologous Transequatorial Loops
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-22
    Jie Chen, Alexei A. Pevtsov, Jiangtao Su, Robertus Erdélyi, Yuanyong Deng, Shangbin Yang, Yongliang Song

    The formation mechanism of two homologous transequatorial loops (TLs) of July 7–8, 1999 (SOL1999-07-07) is studied. The TLs connected active region AR 8614 from the northern hemisphere to AR 8626 in the southern hemisphere. The first TL appeared as a distinct structure at 12:49 UT on July 7, the second TL appeared at 06:21 UT, on July 8. Important results are obtained in this analysis: (i) The configuration

    更新日期:2020-04-23
  • Comparative Study of a Sunspot at Two Different Instances of Time
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-22
    Hashem Hamedivafa

    We investigate the evolutionary effects on the brightness of a sunspot as well as on the properties of its fine-structures using two sets of time series of G-band images of a single sunspot in NOAA 10944 recorded at two symmetric locations on the solar disc by Hinode/SOT (Solar Optical Telescope). The second time series (phase W) was recorded 2.5 d after recording the first time series (phase E). Both

    更新日期:2020-04-23
  • Physical Characteristics of Umbral Dots Derived from a High-Resolution Observations
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-21
    Ali Kilcik, Volkan Sarp, Vasyl Yurchyshyn, Jean-Pierre Rozelot, Atila Ozguc

    The aim of this study is to revisit the physical parameters of umbral dots (UDs) with the latest high-resolution observations and contribute to the scientific understanding of their formation and evolution. In this study, we applied a particle tracking algorithm for detecting UDs in NOAA AR 12384 observed on June 14, 2015 by the Goode Solar Telescope (GST). We analyzed average position distributions

    更新日期:2020-04-22
  • HATS: A Ground-Based Telescope to Explore the THz Domain
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-20
    C. Guillermo Giménez de Castro, Jean-Pierre Raulin, Adriana Valio, Guilherme Alaia, Vinicius Alvarenga, Emilio Carlos Bortolucci, Silvia Helena Fernandes, Carlos Francile, Tiago Giorgetti, Amauri Shossei Kudaka, Fernando Marcelo López, Rogério Marcon, Adolfo Marun, Márcio Zaquela

    The almost unexplored frequency window from submillimeter to mid-infrared (mid-IR) may bring new clues about the particle acceleration and transport processes and the atmospheric thermal response during solar flares. Because of its technical complexity and the special atmospheric environment needed, observations at these frequencies are very sparse. The High Altitude THz Solar Photometer (HATS) is

    更新日期:2020-04-22
  • A Survey of Computational Tools in Solar Physics
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-20
    Monica G. Bobra, Stuart J. Mumford, Russell J. Hewett, Steven D. Christe, Kevin Reardon, Sabrina Savage, Jack Ireland, Tiago M. D. Pereira, Bin Chen, David Pérez-Suárez

    The SunPy Project developed a 13-question survey to understand the software and hardware usage of the solar-physics community. Of the solar-physics community, 364 members across 35 countries responded to our survey. We found that \(99\pm 0.5\)% of respondents use software in their research and 66% use the Python scientific-software stack. Students are twice as likely as faculty, staff scientists, and

    更新日期:2020-04-22
  • A Geoeffective CME Caused by the Eruption of a Quiescent Prominence on 29 September 2013
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-17
    V. V. Grechnev, I. V. Kuzmenko

    The eruption of a large prominence that occurred away of active regions in the SOL2013-09-29 event produced a fast coronal mass ejection (CME) and a shock wave. The event caused considerable geospace disturbances, including a proton enhancement that have been addressed in previous studies. Continuing with the analysis of this event, we focus on the development of the CME and shock wave, assess an expected

    更新日期:2020-04-22
  • Large-Scale Solar Magnetic Fields Observed with the Infrared Spectro-Polarimeter IRmag at the National Astronomical Observatory of Japan: Comparison of Measurements Made in Different Spectral Lines and Observatories
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-15
    M. L. Demidov, Y. Hanaoka, T. Sakurai, X. F. Wang

    This study presents the results of a quantitative analysis of IRmag (infrared Stokes spectro-polarimeter, National Astronomical Observatory of Japan, (NAOJ)/Mitaka) observations in three spectral lines Fe i 1564.8 nm, Si i 1082.72 nm, He i 1083.0 nm, and comparison between IRmag magnetograms and ones from the Solar Dynamic Observatory/Helioseismic and Magnetic Imager (SDO/HMI), Global Oscillation Network

    更新日期:2020-04-22
  • Temporal and Spatial Scales in Coronal Rain Revealed by UV Imaging and Spectroscopic Observations
    Sol. Phys. (IF 2.503) Pub Date : 2020-04-07
    Ryohtaroh T. Ishikawa, Yukio Katsukawa, Patrick Antolin, Shin Toriumi

    Coronal rain corresponds to cool and dense clumps in the corona accreting towards the solar surface; it is often observed above solar active regions. These clumps are generally thought to be produced by a thermal instability in the corona and their lifetime is limited by the time they take to reach the chromosphere. Although the rain usually fragments into smaller clumps while falling down, their specific

    更新日期:2020-04-22
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