Article
Astronomy & Astrophysics
S. Marchenko, S. Criscuoli, M. T. DeLand, D. P. Choudhary, G. Kopp
Summary: On solar rotation timescales, the upper Balmer line activity indices closely follow variations in the total solar irradiance, deviating from the behavior of the line activity indices that track chromospheric activity levels, especially during passages of big sunspot groups.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
K. Kosak, R. Kiefer, A-M Broomhall
Summary: This study investigates the variation of pseudo-mode frequencies with solar activity during the solar cycle. The results show that acoustic oscillation frequencies are correlated with the solar cycle, while pseudo-mode frequencies vary in antiphase. The analysis is based on data from different instruments, and the findings reveal differences in the frequency variations between the instruments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V. M. S. Carrasco, H. Hayakawa, C. Kuroyanagi, M. C. Gallego, J. M. Vaquero
Summary: The study compared the solar activity levels of the Maunder Minimum in 1709 with the Dalton Minimum and recent solar cycles, finding that 1709, while one of the most active years, was less active compared to other years in those periods. This provides robust evidence of low solar activity levels in the Maunder Minimum.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
I. O. I. Virtanen, A. A. Pevtsov, I. I. Virtanen, K. Mursula
Summary: Researchers constructed additional active regions and applied them to the far-side of the Sun in an SFT simulation to assess the possible effects and the magnitude of error that the missing far-side flux causes. The results showed that adding active regions with short lifetimes to the far-side of the Sun results in significantly stronger polar fields in minimum times and slightly delayed polarity reversals.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
X. J. Zhang, L. H. Deng, Y. Fei, C. Li, X. A. Tian, Z. J. Wan
Summary: Hemispheric asymmetry of solar magnetic structures is an important feature of solar cycles. A long-term study using data from the National Astronomical Observatory of Japan reveals a correlation between the sunspot relative numbers and international sunspot numbers, suggesting periodic variations in hemispheric asymmetry. The findings provide insights into the mechanism responsible for the generation and variation of hemispheric coupling in the Sun.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
I. Poljancic Beljan, R. Jurdana-Sepic, T. Jurkic, R. Brajsa, I. Skokic, D. Sudar, D. Ruzdjak, D. Hrzina, W. Poetzi, A. Hanslmeier, A. M. Veronig
Summary: This study examines the relationship between solar differential rotation and activity, revealing patterns of variation in different phases of the solar cycle and comparing these findings with previous theoretical studies.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
V. V. Zharkova, I Vasilieva, E. Popova, S. J. Shepherd
Summary: We study the relationship between the averaged sunspot numbers (SSN) and a modulus summary curve (MSC) obtained from principal component analysis of the solar background magnetic field (SBMF). The MSC is closely correlated with the whole set of SSN, except for discrepancies in a few cycles in the 18th and 19th centuries. Wavelet and Fourier analysis reveal a prominent 10.7-year cycle in both SSN and MSC series, but the SSN series also show a 101-year cycle while the MSC series show a 342-year cycle close to the red-noise level. The correlation coefficients between SSN and MSC vary depending on the data sets, indicating their close but not identical relationship representing different entities of solar activity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
V. N. Nived, E. Scullion, J. G. Doyle, R. Susino, P. Antolin, D. Spadaro, C. Sasso, S. Sahin, M. Mathioudakis
Summary: In this study, we investigate the properties of coronal loop foot-point heating with high resolution observations. We find that the number density near the foot-points in the active region is higher than in the quiet Sun region. Numerical simulations show that a certain number of spicules are required to reproduce the synthetic AIA 171 angstrom signatures.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Soumyaranjan Dash, Dibyendu Nandy, Ilya Usoskin
Summary: This study utilizes simulations and observational data to reveal the impact of magnetic fields generated by the Sun's internal dynamo mechanism on the variations of the solar corona and the state of the heliosphere, establishing causality between solar internal variations and the state of the heliosphere.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Mirkan Y. Kalkan, Diaa E. Fawzy, A. Talat Saygac
Summary: This study presents new prediction models for the 11-year solar activity cycles 25 and 26, using non-linear autoregressive exogenous neural network approach. The models are based on multiple activity indicator parameters, including sunspot number, flare occurrence frequency, solar radio flux, and total solar irradiance. The models accurately predict peak activity values with an accuracy of about 90%. The predicted solar peaks for cycles 25 and 26 are expected to occur in February 2025 and October 2036, respectively.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Valentina Abramenko
Summary: The observational evidence suggests that the turbulent component of the solar dynamo has a significant impact on the generation of solar flares, especially during the second peak and descending phase of a solar cycle. These irregular active regions contribute more to the flaring, indicating a pronounced influence of the turbulent component during specific phases of the solar cycle. This is in line with the concept of the essential role of non-linearities and turbulent intermittence in magnetic fields generation inside the convective zone.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
I. G. Usoskin, S. K. Solanki, N. A. Krivova, B. Hofer, G. A. Kovaltsov, L. Wacker, N. Brehm, B. Kromer
Summary: Using recently obtained C-14 data and state-of-the-art models, individual solar cycles for the last millennium were successfully reconstructed, more than doubling the number of known solar cycles, providing a solid basis for new studies of solar variability.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Engineering, Aerospace
Somayeh Taran, Edris Khodakarami, Hossein Safari
Summary: This study utilizes a complex network approach to investigate the asymmetric activity of solar flares in the two hemispheres. By constructing networks and analyzing node characteristics, it is found that there are central hubs of flare activity in the low latitudes of the southern hemisphere, while the northern hemisphere network exhibits more central hubs. The study reveals that flares form a self-organized criticality system, and each flare plays a significant role in the occurrence of subsequent flares on the solar surface.
ADVANCES IN SPACE RESEARCH
(2022)
Article
Astronomy & Astrophysics
V. N. Obridko, M. M. Katsova, D. D. Sokoloff
Summary: The cyclic activity on the Sun and stars, and the generation of magnetic field are primarily explained by a dynamo mechanism. An alternative view suggests that the gravitational influence of the planetary system, especially Jupiter, plays a role in field generation. However, comparisons between exoplanet characteristics and associated star activity variations did not show any relationship, leading to the belief that strong gravitational influence may eliminate cyclic variation in stellar activity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Manon Jarry, Alexis P. Rouillard, Illya Plotnikov, Athanasios Kouloumvakos, Alexander Warmuth
Summary: This study analyzes the geometrical and kinematic properties of coronal and interplanetary shock waves produced by CMEs. The results show the evolution of the shock wave's shape, expansion speeds, and their correlation with the underlying flare activity. These findings contribute to improving space weather forecasting and understanding the eruption process of CMEs.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Papaioannou, A. Kouloumvakos, A. Mishev, R. Vainio, I Usoskin, K. Herbst, A. P. Rouillard, A. Anastasiadis, J. Gieseler, R. Wimmer-Schweingruber, P. Kuehl
Summary: This study reports the first relativistic solar proton event of solar cycle 25, identifies the solar origin of the event through various observational methods, and demonstrates different time profiles with anisotropic characteristics. Notably, the event exhibits a moderately hard rigidity spectrum at high energies.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Geochemistry & Geophysics
Charlotte L. Pearson, Steven W. Leavitt, Bernd Kromer, Sami K. Solanki, Ilya Usoskin
Summary: Dendrochronology and radiocarbon (C-14) dating have been intertwined since the 1950s, with tree-ring date samples playing a crucial role in calibrating the C-14 timescale. These methods continue to shape and improve chronological frameworks worldwide, answering questions across various scientific fields.
Article
Chemistry, Multidisciplinary
Panagiota Makrantoni, Anastasia Tezari, Argyris N. Stassinakis, Pavlos Paschalis, Maria Gerontidou, Pantelis Karaiskos, Alexandros G. Georgakilas, Helen Mavromichalaki, Ilya G. Usoskin, Norma Crosby, Mark Dierckxsens
Summary: The ionization of the Earth's atmosphere induced by cosmic radiation during recent solar cycles was globally studied using the CRAC:CRII model. The study found that galactic cosmic rays constitute the main source of ionization in the Earth's atmosphere and significantly contribute to radiation exposure inside the atmosphere. Specific altitudes of interest, such as those commonly used by commercial aviation, were also focused on.
APPLIED SCIENCES-BASEL
(2022)
Article
Astronomy & Astrophysics
O. Raukunen, I Usoskin, S. Koldobskiy, G. Kovaltsov, R. Vainio
Summary: This study revisits the derivation of annual integral solar energetic particle (SEP) fluxes using in situ measurements from 1984 to 2019. The results show that solar cycle 24 had significantly weaker SEP fluence compared to cycles 22 and 23. The cumulative occurrence probability of SEP fluence above a certain value is perfectly described by the Weibull distribution, providing a projection for the occurrence of solar extreme eruptive events on longer timescales.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Meteorology & Atmospheric Sciences
K. Golubenko, E. Rozanov, G. Kovaltsov, I Usoskin
Summary: This study computed the production of cosmogenic isotopes in the Earth's atmosphere using the CRAC model, providing zonal mean production rates for different latitudinal zones in the stratosphere and troposphere. The results indicate that isotope production by solar energetic particles in the tropical zone is small and can be neglected.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Astronomy & Astrophysics
Soumyaranjan Dash, Dibyendu Nandy, Ilya Usoskin
Summary: This study utilizes simulations and observational data to reveal the impact of magnetic fields generated by the Sun's internal dynamo mechanism on the variations of the solar corona and the state of the heliosphere, establishing causality between solar internal variations and the state of the heliosphere.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Astronomy & Astrophysics
Akash Biswas, Bidya Binay Karak, Ilya Usoskin, Eckhard Weisshaar
Summary: Solar activity has a cyclic nature, with the 11-year Schwabe cycle dominating its variability on the interannual timescale. However, solar cycles can vary significantly in length, shape, and magnitude, from grand minima to grand maxima. The limited length and inhomogeneous quality of direct sunspot-number series necessitates the use of cosmogenic-isotope proxy to study long-term solar variability. This article provides a brief overview of the long-term variability of solar activity at centennial - millennial timescales, discussing the occurrence of grand minima and maxima, as well as quasi-periodicities such as the Gleissberg, Suess/de Vries, and Hallstatt cycles. It also reviews theoretical perspectives on the observed features in the context of dynamo models, highlighting the importance of nonlinearities and stochastic fluctuations.
SPACE SCIENCE REVIEWS
(2023)
Review
Astronomy & Astrophysics
Ilya G. Usoskin
Summary: In this article, the authors review the current understanding of long-term solar activity on a multi-millennial timescale through indirect proxy methods. The concept of solar activity is explained, along with an overview of indices used to quantify different aspects of variable solar activity, with a focus on sunspot numbers. The historical development and modern state of proxy-based reconstructions of past solar activity are discussed, emphasizing the use of cosmogenic isotopes C-14 and Be-10. The article concludes with the main features of long-term solar magnetic activity and their implications for solar/stellar dynamo theory.
LIVING REVIEWS IN SOLAR PHYSICS
(2023)
Article
Astronomy & Astrophysics
Nicholas Larsen, Alexander Mishev, Ilya Usoskin
Summary: We introduce a new open-source tool OTSO for modeling cosmic ray propagation in the Earth's geomagnetosphere and demonstrate its application in several events. Comparison with widely used tools and validation show good agreement. The tool is also used to provide necessary background for analyzing two notable ground-level enhancements.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Sergey Koldobskiy, Florian Mekhaldi, Gennady Kovaltsov, Ilya Usoskin
Summary: Extreme solar particle events (ESPEs) are rare and powerful processes of solar eruptive activity. This study presents a new method to reconstruct ESPE fluence based on advanced modeling techniques, combining different cosmogenic isotope (CI) data. The reconstructed ESPE fluences have a smoother spectral shape and significantly higher estimates of low-energy fluence, making ESPEs even more dangerous for modern technological systems than previously believed. The fitted modified Band function allows for the application of the obtained results in different fields.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Pauli Vaisanen, Ilya Usoskin, Riikka Kahkonen, Sergey Koldobskiy, Kalevi Mursula
Summary: Galactic cosmic rays (GCRs) collide with atmospheric constituents, generating showers of secondary particles in the Earth's atmosphere. The flux of GCRs near Earth is influenced by solar magnetic activity and geomagnetic shielding. A global network of ground-based neutron monitors (NMs) has continuously monitored the variability of GCR flux since the 1950s. This study provides an updated and extended reconstruction of the heliospheric modulation potential using a new method and measurements from high-latitude NMs.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Review
Astronomy & Astrophysics
Aimee Norton, Rachel Howe, Lisa Upton, Ilya Usoskin
Summary: This article describes the defining observations of the solar cycle and their constraints on the dynamo processes within the Sun. It covers topics such as sunspot numbers, active region flux ranges and lifetimes, bipolar magnetic region tilt angles, Hale and Joy's law, and various other aspects.
SPACE SCIENCE REVIEWS
(2023)
Article
Astronomy & Astrophysics
Sanja Panovska, Stepan Poluianov, Jiawei Gao, Monika Korte, Alexander Mishev, Yuri Y. Shprits, Ilya Usoskin
Summary: The production rates of cosmogenic radionuclides in the Earth's atmosphere vary with the Earth's geomagnetic field and solar activity. This study estimated the production rates of several cosmogenic nuclides for the past 100,000 years based on global, time-dependent geomagnetic field models and moderate solar activity. The results showed that the production rates were high during the Laschamps geomagnetic excursion, with no notable latitudinal dependence. Hemispheric asymmetry and persistent overall time ranges were observed in the production rates predicted by the geomagnetic field models.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Environmental Sciences
Thomas Reddmann, Miriam Sinnhuber, Jan Maik Wissing, Olesya Yakovchuk, Ilya Usoskin
Summary: A possible impact of an extreme solar particle event (ESPE) on the middle atmosphere has been studied, considering present-day climate and geomagnetic conditions. The study reveals that the impact of ESPE on the atmosphere is greater compared to an extreme geomagnetic storm (GMS). This research is important in revealing the potential hazards of solar particle events on the atmosphere.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2023)
Article
Astronomy & Astrophysics
Leon Kocharov, Alexander Mishev, Esa Riihonen, Rami Vainio, Ilya Usoskin
Summary: Major solar eruptions can generate solar particle events that can be detected by neutron monitors worldwide. This study analyzes the similarities between two events with similar time profiles and explores the relationship between the events and their progenitor solar flares and coronal mass ejections. The results suggest that a single solar eruption can contribute to multiple components of solar energetic particles.
ASTROPHYSICAL JOURNAL
(2023)
