139 citations · 986 across the 53 of their papers we have counts for
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Reconstructing solar magnetic fields from historical observations X. Effect of magnetic field inclination and boundary structure on AIA 1600 Å emission
Ismo Tähtinen, Alexei A. Pevtsov, Timo Asikainen +1
The relation between the intensity of chromospheric emissions and the photospheric magnetic field strength has been examined in several studies, but the effect of the magnetic fiel…
Transition to a weaker Sun: Changes in the solar atmosphere during the decay of the Modern Maximum
K. Mursula, A. A. Pevtsov, T. Asikainen +2
The Sun experienced a period of unprecedented activity during the 20th century, now called the Modern Maximum (MM). The decay of the MM after cycle 19 has changed the Sun, the heli…
A Universal Method for Solar Filament Detection from H-alpha Observations using Semi-supervised Deep Learning
Andrea Diercke, Robert Jarolim, Christoph Kuckein +7
Filaments are omnipresent features in the solar atmosphere. Their location, properties and time evolution can provide information about changes in solar activity and assist the ope…
Ground-based Solar Observations for Space Weather Forecasting
A. G. Tlatov, A. A. Pevtsov
The possibilities of organizing an observation service for solar activity in order to provide space weather forecasting are considered. The most promising at this stage is the crea…
Variation of small scale magnetic fields over a century using Ca-K images as proxy
Jagdev Singh, Muthu Priyal, B. Ravindra +2
A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory (KO), Mount Wilson Observatory (MWO), and Mauna Loa Solar Observatory (MLSO) were used to ide…
Re-calibration of the Sunspot Number: Status Report
F. Clette, L. Lefèvre, T. Chatzistergos +18
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and Group sunspot number (GN) following the release of version 2.0 of SN in 2015. This report consti…
Reconstructing solar magnetic fields from historical observations VIII. AIA 1600 Å contrast as a proxy of solar magnetic fields
Ismo Tähtinen, Ilpo Virtanen, Alexei A. Pevtsov +1
The bright regions in the solar chromosphere and temperature minimum have a good spatial correspondence with regions of intense photospheric magnetic field. Their observation start…
Continuous Solar Observations from the Ground -- Assessing Duty Cycle from GONG Observations
Kiran Jain, Sushant C. Tripathy, Frank Hill +1
Continuous observations play an important role in the studies of solar variability. While such observations can be achieved from space with almost 100% duty cycle, it is difficult…
On a limitation of Zeeman polarimetry and imperfect instrumentation in representing solar magnetic fields with weaker polarization signal
Alexei A. Pevtsov, Yang Liu, Ilpo Virtanen +4
Full disk vector magnetic fields are used widely for developing better understanding of large-scale structure, morphology, and patterns of the solar magnetic field. The data are al…
The intensity and evolution of the extreme storms in January 1938
Hisashi Hayakawa, Kentaro Hattori, Alexei A. Pevtsov +7
Major solar eruptions occasionally direct interplanetary coronal mass ejections (ICMEs) to Earth and cause significant geomagnetic storms and low-latitude aurorae. While single ext…
The effect of telescope aperture, scattered light, and human vision on early measurements of sunspot and group numbers
Nina V. Karachik, Alexei A. Pevtsov, Yury A. Nagovitsyn
Early telescopic observations of sunspots were conducted with instruments of relatively small aperture. These instruments also suffered from a higher level of scattered light, and…
Evolution of Magnetic Helicity in Solar Cycle 24
Valery V. Pipin, Alexei A. Pevtsov, Yang Liu +1
We propose a novel approach to reconstruct the surface magnetic helicity density on the Sun or sun-like stars. The magnetic vector potential is determined via decomposition of vect…
Extended statistical analysis of emerging solar active regions
A. S. Kutsenko, V. I. Abramenko, A. A. Pevtsov
We use observations of line-of-sight magnetograms from Helioseismic and Magnetic Imager (HMI) on board of Solar Dynamics Observatory (SDO) to investigate polarity separation, magne…
Roadmap for Reliable Ensemble Forecasting of the Sun-Earth System
Gelu Nita, Rafal Angryk, Berkay Aydin +44
The authors of this report met on 28-30 March 2018 at the New Jersey Institute of Technology, Newark, New Jersey, for a 3-day workshop that brought together a group of data provide…
Search for a Signature of Twist-Removal in the Magnetic Field of Sunspots in Relation with Major Flares
Olga Burtseva, Sanjay Gosain, Alexei A. Pevtsov
We investigate the restructuring of the magnetic field in sunspots associated with two flares: the X6.5 flare on 6 December 2006 and the X2.2 flare on 15 February 2011. The observe…
Ca II K 1-A Emission Index Composites
Luca Bertello, Andrew R. Marble, Alexei A. Pevtsov
We describe here a procedure to combine measurements in the 393.37 nm Ca II K spectral line taken at different observatories. Measurements from the National Solar Observatory (NSO)…
The Mount Wilson Observatory S-index of the Sun
Ricky Egeland, Willie Soon, Sallie Baliunas +3
The most commonly used index of stellar magnetic activity is the instrumental flux scale of singly-ionized calcium H & K line core emission, S, developed by the Mount Wilson Observ…
Dynamo Sensitivity in Solar Analogs with 50 Years of Ca II H & K Activity
Ricky Egeland, Willie Soon, Sallie Baliunas +3
The Sun has a steady 11-year cycle in magnetic activity most well-known by the rising and falling in the occurrence of dark sunspots on the solar disk in visible bandpasses. The 11…
Long-term variations in sunspot magnetic field - area relation
Yury A. Nagovitsyn, Alexei A. Pevtsov, Aleksandra A. Osipova
Using observations of sunspot magnetic field strengths (H) from the Crimean Astrophysical Observatory (CrAO) and area (S) of sunspots from the Kislovodsk Mountain Astronomical Stat…
Correlation Between Sunspot Number and ca II K Emission Index
Luca Bertello, Alexei A. Pevtsov, Andrey Tlatov +1
Long-term synoptic observations in the resonance line of Ca II K constitute a fundamental database for a variety of retrospective analyses of the state of the solar magnetism. Syno…
The Minimum of Solar Cycle 23: As Deep as It Could Be?
Andrés Muñoz-Jaramillo, Ryan R. Senkpeil, Dana W. Longcope +5
In this work we introduce a new way of binning sunspot group data with the purpose of better understanding the impact of the solar cycle on sunspot properties and how this defined…
Hard X-ray Emission During Flares and Photospheric Field Changes
O. Burtseva, J. C. Martínez-Oliveros, G. J. D. Petrie +1
We study the correlation between abrupt permanent changes of magnetic field during X-class flares observed by the GONG and HMI instruments, and the hard X-ray (HXR) emission observ…
Application of Mutual Information Methods in Time-Distance Helioseismology
Dustin Keys, Shukur Kholikov, Alexei Pevtsov
We apply a new technique, the mutual information (MI) from information theory, to time-distance helioseismology, and demonstrate that it can successfully reproduce several classic…
SOLIS: reconciling disk-integrated and disk-resolved spectra from the Sun
Alexei Pevtsov, Luca Bertello, Brian Harker +2
Unlike other stars, the surface of the Sun can be spatially resolved to a high degree of detail. But the Sun can also be observed as if it was a distant star. The availability of s…