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Universe
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Solar and Stellar Activity: Exploring the Cosmic Nexus
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Solar and Stellar Activity: Exploring the Cosmic Nexus

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Space Science".

Deadline for manuscript submissions: closed (31 May 2024) | Viewed by 8746

Special Issue Editors

Dr. Emese Forgacs-Dajka

E-Mail Website
Guest Editor
Department of Astronomy, Eötvös University, H-1117 Budapest, Hungary
Interests: astrophysical HD/MHD; solar physics; planetary systems
Dr. Zsofia Bebesi

E-Mail Website
Guest Editor
Department of Space Physics and Technology, Wigner Research Centre for Physics, H-1121 Budapest, Hungary
Interests: space plasma physics; space weather

Special Issue Information

Dear Colleagues,

Sun and the star activity is closely related to the cosmic environment in which they exist. This Special Issue on “Solar and Stellar Activity: Exploring the Cosmic Nexus” provides an opportunity to present the latest research on our Sun, its immediate environment (the heliosphere) and the activity of stars and its effects. Hence, the topic of this Special Issue is to review the variation and variability in various phenomena in space sciences. Sophisticated theoretical and numerical modeling techniques present a unique opportunity to combine several space and ground-based observations to understand the changes and connections in the surrounding space, from the nearest star (our Sun) to distant stars.

This following topics can be found in this Special Issue:

  • The observation of magnetic phenomena in our Sun and other stars and their origin and evolution;
  • The heating of solar and stellar coronae;
  • The impact of activity phenomena on their environment in the heliosphere or in the astrospheres;
  • Space weather prediction using coordinated observations of various spacecraft in the inner heliosphere, the vicinity of Earth and ongoing space missions at other planets;
  • The effects of space weather on planets, comets and exoplanets.

The aim of this comprehensive Special Issue is to introduce exciting new solar and stellar research that has been gaining ground in recent years. The papers published here present new directions and highlight recent advances in the field, offering deeper insights into the role of space weather in relation with the complexity of stellar dynamics.

Dr. Emese Forgacs-Dajka
Dr. Zsofia Bebesi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • astrophysical HD/MHD
  • solar and stellar activity
  • space weather
  • solar and stellar dynamo

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Published Papers (10 papers)

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Research

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11 pages, 535 KiB  
Article
Predicting Solar Cycles with a Parametric Time Series Model
by Kristof Petrovay
Universe 2024, 10(9), 364; https://doi.org/10.3390/universe10090364 - 11 Sep 2024
Viewed by 542
Abstract
The objective of this paper is to reproduce and predict the series of solar cycle amplitudes using a simple time-series model that takes into account the variable time scale of the Gleissberg oscillation and the absence of clear evidence for odd–even alternation prior [...] Read more.
The objective of this paper is to reproduce and predict the series of solar cycle amplitudes using a simple time-series model that takes into account the variable time scale of the Gleissberg oscillation and the absence of clear evidence for odd–even alternation prior to Solar Cycle 9 (SC9). It is demonstrated that the Gleissberg oscillation can be quite satisfactorily modelled as a sinusoidal variation of constant amplitude with a period increasing linearly with time. Subtracting this model from the actual cycle amplitudes, a clear even–odd alternating pattern is discerned in the time series of the residuals since SC9. For this period of time, the mean value of the residuals for odd-numbered cycles is shown to exceed the value for even-numbered cycles by more than 4σ, providing the clearest evidence yet for a persistent odd–even–odd alternation in cycle amplitudes. Random deviations from these means are less than half the standard deviation of the raw cycle amplitude time series for the same period, which allows the use of these regularities for solar cycle prediction with substantially better confidence than the simple climatological average. Predicted cycle amplitudes are found to be robust against the addition or omission of some data points from the input set, and the method correctly hindcasts SC23 and SC24. The potential physical background of the regularities is also discussed. Our predictions for the amplitudes of SC25, SC26, and SC27 are 155.8±20.7, 96.9±25.1 and 140.8±20.7, respectively. This suggests that the amplitude of SC26 will be even lower than that of SC24, making it the weakest cycle since the Dalton Minimum. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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22 pages, 10210 KiB  
Article
Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe
by Kitti Alexandra Berényi, Loredana Perrone, Dario Sabbagh, Carlo Scotto, Alessandro Ippolito, Árpád Kis and Veronika Barta
Universe 2024, 10(9), 344; https://doi.org/10.3390/universe10090344 - 27 Aug 2024
Viewed by 697
Abstract
A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16–20 March 2015 for the ICME-driven storm and [...] Read more.
A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16–20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h’F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N2 ratio. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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17 pages, 1724 KiB  
Article
Slow Body MHD Waves in Inhomogeneous Photospheric Waveguides
by Istvan Ballai, Fisal Asiri, Viktor Fedun, Gary Verth, Emese Forgács-Dajka and Abdulrahman B. Albidah
Universe 2024, 10(8), 334; https://doi.org/10.3390/universe10080334 - 21 Aug 2024
Viewed by 553
Abstract
The present study deals with the investigation of the oscillatory morphology of guided slow body MHD modes in inhomogeneous magnetic waveguides that appear in the solar photospheric plasmas in the forms of pores or sunspots. The eigenvalues and eigenfunctions related to these waves [...] Read more.
The present study deals with the investigation of the oscillatory morphology of guided slow body MHD modes in inhomogeneous magnetic waveguides that appear in the solar photospheric plasmas in the forms of pores or sunspots. The eigenvalues and eigenfunctions related to these waves in an isothermal plasma are obtained numerically by solving a Sturm-Liouville problem with Dirichlet boundary conditions set at the boundary of the waveguide. Our results show that the inhomogeneities in density (pressure) and magnetic field have a strong influence on the morphology of waves, and higher-order more are sensitive to the presence of inhomogeneity. Our results suggest that he identification of modes just by a simple visual inspection can lead to a misinterpretation of the nature of modes. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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22 pages, 3326 KiB  
Article
CME Forecasting System: Event Selection Algorithm, Dimming Data Application Limitations, and Analysis of the Results for Events of the Solar Cycle 24
by Ksenia Kaportseva, Yulia Shugay, Anna Vakhrusheva, Vladimir Kalegaev, Anton Shiryaev and Valeriy Eremeev
Universe 2024, 10(8), 321; https://doi.org/10.3390/universe10080321 - 9 Aug 2024
Viewed by 851
Abstract
The modeling of coronal mass ejections (CMEs) arrival to Earth was carried out using a one-dimensional drag-based model (DBM) over the period from 2010 to 2018. The CME propagation model includes a simulation of the interaction of the CME with background solar wind [...] Read more.
The modeling of coronal mass ejections (CMEs) arrival to Earth was carried out using a one-dimensional drag-based model (DBM) over the period from 2010 to 2018. The CME propagation model includes a simulation of the interaction of the CME with background solar wind via the quasi-stationary solar wind (QSW) model. An analysis of the results of forecasting CME speed and time of arrival to Earth was performed. Input data were obtained from the CACTus database. To ensure real-time operation, a new algorithm was established to select events that can reach Earth more likely. Coronal dimming data were used to obtain coordinates of the CME source location. Forecasting results have been compared with interplanetary CME (ICME) catalogs. The system has predicted 189 of 280 events (68%), with a tolerance of 48 h for the period of maximum solar activity (from 2010 to 2015). The average absolute error of predicted CME arrival speed is about 90 km/s. Our system has predicted 80% of ICMEs associated with extreme geomagnetic storms (Dstmin ≤ −100 nT) within a tolerance of 24 h. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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24 pages, 801 KiB  
Article
Lifetime of Long-Lived Sunspot Groups
by Judit Muraközy
Universe 2024, 10(8), 318; https://doi.org/10.3390/universe10080318 - 5 Aug 2024
Viewed by 645
Abstract
Studies of active region (AR) lifetimes are mostly restricted to short-lived ARs. The aim of this paper is to include recurrent ARs, which should be identified unambiguously. The first step is the algorithmic listing of possible returns; then, the candidates are visually checked [...] Read more.
Studies of active region (AR) lifetimes are mostly restricted to short-lived ARs. The aim of this paper is to include recurrent ARs, which should be identified unambiguously. The first step is the algorithmic listing of possible returns; then, the candidates are visually checked using the unique HTML-feature of the Debrecen sunspot database. The final step is application of an asymmetric Gaussian function, introduced in previous articles, for short-lived ARs. This function has a surprisingly good fit to the data on correctly identified recurrent sunspot groups over several rotations enabling the reconstruction of the development on the far side of the sun. The Gnevyshev–Waldmeier rule for the area–lifetime relationship is not applicable for recurrent ARs; however, as a novel approach, a linear regression analysis extended to long lifetimes made it possible to recognize two populations of sizes for which two different area–lifetime relationships can be obtained. The lifetimes exhibit weak dependencies on the heliographic latitude and solar cycle phase. If an asymmetric Gaussian cannot be fit to the data, then they presumably belong to consecutive members of an active nest. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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18 pages, 5090 KiB  
Article
Altitude Heterogeneity of Magnetic Fields and Doppler Velocities in the Area of Seismic Source of a Strong Solar Flare from Data in Helium, Sodium, and Nickel Lines
by Ivan I. Yakovkin, Natalia I. Lozitska and Vsevolod G. Lozitsky
Universe 2024, 10(6), 262; https://doi.org/10.3390/universe10060262 - 14 Jun 2024
Viewed by 740
Abstract
Measurements of magnetic fields near seismic sources during solar flares are vital for understanding the dynamics of solar activity. We used spectropolarimetric observations of the X17.2/4B solar flare on 28 October 2003, over a wavelength interval of 43 Å, including the D3, D2, [...] Read more.
Measurements of magnetic fields near seismic sources during solar flares are vital for understanding the dynamics of solar activity. We used spectropolarimetric observations of the X17.2/4B solar flare on 28 October 2003, over a wavelength interval of 43 Å, including the D3, D2, D1, and Ni I 5892.88 Å lines, to analyze the Stokes I ± V profiles. Effective magnetic fields within 0.5–1.5 kG were measured in the D1, D2, and D3 lines at different flare locations, with the photospheric Ni I 5892.88 Å line showing a weaker field of below 0.5 kG. The D3 line showed rapid plasma descents of up to 11 km/s, in contrast to the slower velocities within 2.3 km/s observed in other lines. The differing amplitudes in the I + V and I − V profiles indicated potential non-Zeeman polarization effects. Secondary Stokes V peaks were also detected up to 8 Å from the D3 emission core. Significant altitudinal inhomogeneity in the magnetic field strengths was detected, possibly indicating the local magnetic collapse, facilitating the Lorentz-force driven mechanism of the seismic source excitation. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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16 pages, 1464 KiB  
Article
Classification of Major Solar Flares from Extremely Imbalanced Multivariate Time Series Data Using Minimally Random Convolutional Kernel Transform
by Kartik Saini, Khaznah Alshammari, Shah Muhammad Hamdi and Soukaina Filali Boubrahimi
Universe 2024, 10(6), 234; https://doi.org/10.3390/universe10060234 - 24 May 2024
Cited by 3 | Viewed by 1108
Abstract
Solar flares are characterized by sudden bursts of electromagnetic radiation from the Sun’s surface, and are caused by the changes in magnetic field states in active solar regions. Earth and its surrounding space environment can suffer from various negative impacts caused by solar [...] Read more.
Solar flares are characterized by sudden bursts of electromagnetic radiation from the Sun’s surface, and are caused by the changes in magnetic field states in active solar regions. Earth and its surrounding space environment can suffer from various negative impacts caused by solar flares, ranging from electronic communication disruption to radiation exposure-based health risks to astronauts. In this paper, we address the solar flare prediction problem from magnetic field parameter-based multivariate time series (MVTS) data using multiple state-of-the-art machine learning classifiers that include MINImally RandOm Convolutional KErnel Transform (MiniRocket), Support Vector Machine (SVM), Canonical Interval Forest (CIF), Multiple Representations Sequence Learner (Mr-SEQL), and a Long Short-Term Memory (LSTM)-based deep learning model. Our experiment is conducted on the Space Weather Analytics for Solar Flares (SWAN-SF) benchmark data set, which is a partitioned collection of MVTS data of active region magnetic field parameters spanning over nine years of operation of the Solar Dynamics Observatory (SDO). The MVTS instances of the SWAN-SF dataset are labeled by GOES X-ray flux-based flare class labels, and attributed to extreme class imbalance because of the rarity of the major flaring events (e.g., X and M). As a performance validation metric in this class-imbalanced dataset, we used the True Skill Statistic (TSS) score. Finally, we demonstrate the advantages of the MVTS learning algorithm MiniRocket, which outperformed the aforementioned classifiers without the need for essential data preprocessing steps such as normalization, statistical summarization, and class imbalance handling heuristics. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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20 pages, 3351 KiB  
Article
Combining Empirical and Physics-Based Models for Solar Wind Prediction
by Rob Johnson, Soukaina Filali Boubrahimi, Omar Bahri and Shah Muhammad Hamdi
Universe 2024, 10(5), 191; https://doi.org/10.3390/universe10050191 - 24 Apr 2024
Cited by 1 | Viewed by 1190
Abstract
Solar wind modeling is classified into two main types: empirical models and physics-based models, each designed to forecast solar wind properties in various regions of the heliosphere. Empirical models, which are cost-effective, have demonstrated significant accuracy in predicting solar wind at the L1 [...] Read more.
Solar wind modeling is classified into two main types: empirical models and physics-based models, each designed to forecast solar wind properties in various regions of the heliosphere. Empirical models, which are cost-effective, have demonstrated significant accuracy in predicting solar wind at the L1 Lagrange point. On the other hand, physics-based models rely on magnetohydrodynamics (MHD) principles and demand more computational resources. In this research paper, we build upon our recent novel approach that merges empirical and physics-based models. Our recent proposal involves the creation of a new physics-informed neural network that leverages time series data from solar wind predictors to enhance solar wind prediction. This innovative method aims to combine the strengths of both modeling approaches to achieve more accurate and efficient solar wind predictions. In this work, we show the variability of the proposed physics-informed loss across multiple deep learning models. We also study the effect of training the models on different solar cycles on the model’s performance. This work represents the first effort to predict solar wind by integrating deep learning approaches with physics constraints and analyzing the results across three solar cycles. Our findings demonstrate the superiority of our physics-constrained model over other unconstrained deep learning predictive models. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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Review

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30 pages, 2416 KiB  
Review
Stellar Flares, Superflares, and Coronal Mass Ejections—Entering the Big Data Era
by Krisztián Vida, Zsolt Kővári, Martin Leitzinger, Petra Odert, Katalin Oláh, Bálint Seli, Levente Kriskovics, Robert Greimel and Anna Mária Görgei
Universe 2024, 10(8), 313; https://doi.org/10.3390/universe10080313 - 31 Jul 2024
Cited by 1 | Viewed by 883
Abstract
Flares, sometimes accompanied by coronal mass ejections (CMEs), are the result of sudden changes in the magnetic field of stars with high energy release through magnetic reconnection, which can be observed across a wide range of the electromagnetic spectrum from radio waves to [...] Read more.
Flares, sometimes accompanied by coronal mass ejections (CMEs), are the result of sudden changes in the magnetic field of stars with high energy release through magnetic reconnection, which can be observed across a wide range of the electromagnetic spectrum from radio waves to the optical range to X-rays. In our observational review, we attempt to collect some fundamental new results, which can largely be linked to the Big Data era that has arrived due to the expansion of space photometric observations over the last two decades. We list the different types of stars showing flare activity and their observation strategies and discuss how their main stellar properties relate to the characteristics of the flares (or even CMEs) they emit. Our goal is to focus, without claiming to be complete, on those results that may, in one way or another, challenge the “standard” flare model based on the solar paradigm. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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19 pages, 6411 KiB  
Review
The Hearth of the World: The Sun before Astrophysics
by Gábor Kutrovátz
Universe 2024, 10(6), 256; https://doi.org/10.3390/universe10060256 - 7 Jun 2024
Viewed by 865
Abstract
This paper presents a historical overview of conceptions about the Sun in Western astronomical and cosmological traditions before the advent of spectroscopy and astrophysics. Rather than studying general cultural ideas, we focus on the concepts developed by astronomers or by natural philosophers impacting [...] Read more.
This paper presents a historical overview of conceptions about the Sun in Western astronomical and cosmological traditions before the advent of spectroscopy and astrophysics. Rather than studying general cultural ideas, we focus on the concepts developed by astronomers or by natural philosophers impacting astronomy. The ideas we investigate, from the works of Plato and Aristotle to William Herschel and his contemporaries, do not line up into a continuous and integrated narrative, since the nature of the Sun was not a genuine scientific topic before the nineteenth century. However, the question recurringly arose as embedded in cosmological and physical contexts. By outlining this heterogeneous story that spreads from transcendence to materiality, from metaphysics to physics, from divinity to solar inhabitants, we receive insight into some major themes and trends both in the general development of astronomical and cosmological thought and in the prehistory of modern solar science. Full article
(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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