Flare Activity of the Sun and Variations in its UV Emission During Cycle 24

Sunspots are temporary phenomena on the photosphere of the Sun which appear visibly as dark spots compared to surrounding regions. Sunspot populations usually rise fast but fall more slowly when observed for any particular solar cycle. The sunspot numbers for the current cycle 24 and the previous three cycles have been plotted for duration of first four years for each of them. It appears that the value of peak sunspot number for solar cycle 24 is smaller than the three preceding cycles. When regression analysis is made it exhibits a trend of slow rising phase of the cycle 24 compared to previous three cycles. Our analysis further shows that cycle 24 is approaching to a longer-period but with smaller occurrences of sunspot number.

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Dynamics of the circumpolar magnetic field of the Sun at a maximum of cycle 24

Kinematics and Physics of Celestial Bodies ◽

10.3103/s0884591316020069 ◽

2016 ◽

Vol 32 (2) ◽

pp. 78-85 ◽

Cited By ~ 2

Author(s):

M. I. Pishkalo ◽

U. M. Leiko

Keyword(s):

Magnetic Field ◽

The Sun ◽

Cycle 24

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X-Ray Flares and Activity Complexes on the Sun in Solar Cycle 24

Astronomy Reports ◽

10.1134/s1063772920010035 ◽

2020 ◽

Vol 64 (1) ◽

pp. 58-65 ◽

Cited By ~ 1

Author(s):

E. S. Isaeva ◽

V. M. Tomozov ◽

S. A. Yazev

Keyword(s):

Solar Cycle ◽

The Sun ◽

X Ray ◽

Solar Cycle 24 ◽

Cycle 24

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Synoptic maps in three wavelengths of the Chromospheric Telescope

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319004551 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 339-341

Author(s):

Andrea Diercke ◽

Carsten Denker

Keyword(s):

Time Series ◽

Solar Cycle ◽

Solar Disk ◽

The Sun ◽

Observational Period ◽

Quiet Sun ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Spectral Ranges ◽

Full Disk

Abstracthe Chromospheric Telescope (ChroTel) observes the entire solar disk since 2011 in three different chromospheric wavelengths: Hα, Ca ii K, and He i. The instrument records full-disk images of the Sun every three minutes in these different spectral ranges. The ChroTel observations cover the rising and decaying phase of solar cycle 24. We started analyzing the ChroTel time-series and created synoptic maps of the entire observational period in all three wavelength bands. The maps will be used to analyze the poleward migration of quiet-Sun filaments in solar cycle 24.

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IUE Observations of the Chromospheric Activity-Age Relation in Young Solar-Type Stars

Symposium - International Astronomical Union ◽

10.1017/s007418090002982x ◽

1983 ◽

Vol 102 ◽

pp. 161-164

Author(s):

Theodore Simon ◽

Ann Merchant Boesgaard

Keyword(s):

Magnetic Fields ◽

Flare Activity ◽

The Sun ◽

Late Type ◽

Cool Star ◽

Opportune Time ◽

Solar Type ◽

Age Relation ◽

Relationship Of ◽

The Relationship

The difficulties of measuring magnetic fields in late-type stars other than the sun are well known, as one is reminded by other contributions to these Proceedings. This Symposium nevertheless comes at a very opportune time, as we are now at the point where we can begin to explore the relationship of stellar magnetism to flare activity and quiescent cool star chromospheres, transition regions (TRs), and coronae.

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Super-active regions in solar cycle 24

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000223 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 309-314 ◽

Cited By ~ 1

Author(s):

Anqin Chen ◽

Jingxiu Wang

Keyword(s):

Solar Cycle ◽

Active Regions ◽

Total Solar Irradiance ◽

Flare Activity ◽

Solar Cycles ◽

Solar Cycle 24 ◽

Satisfactory Account ◽

Current Cycle ◽

Flare Index ◽

Cycle 24

AbstractComparing with solar cycles 21-23, the level of solar activity in the current cycle is very low. So far, there have been only five SARs and 45 X class flares. The monthly smoothed total solar irradiance decreased sharply by 0.09% from the maximum of cycle 23 to the minima between cycles 23 and 24. In this contribution, we present new studies on SARs in Cycle 24. The SARs in the current cycle have relatively smaller flare index (Iflare) and composite vector field index (Icom) comparing with the SARs in cycles 22 and 23. There is a clearly linear relationship between Iflare and Icom. The emphasis of this contribution is put on the similarity and different behaviors of vector magnetic fields of the SARs in the current solar cycle and the previous ones. We try to get a satisfactory account for the general characteristics and relatively lower level of solar flare activity in Cycle 24.

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Restructuring of the Solar Magnetic Fields and Flare Activity Centers in Cycle 24

Astronomy Reports ◽

10.1134/s106377292007001x ◽

2020 ◽

Vol 64 (6) ◽

pp. 540-546

Author(s):

A. V. Borovik ◽

A. V. Mordvinov ◽

E. M. Golubeva ◽

A. A. Zhdanov

Keyword(s):

Magnetic Fields ◽

Flare Activity ◽

Solar Magnetic Fields ◽

Cycle 24

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Photospheric activity of the Sun with VIRGO and GOLF

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731560 ◽

2017 ◽

Vol 608 ◽

pp. A87 ◽

Cited By ~ 13

Author(s):

D. Salabert ◽

R. A. García ◽

A. Jiménez ◽

L. Bertello ◽

E. Corsaro ◽

...

Keyword(s):

Solar Activity ◽

Radial Velocity ◽

Wavelength Dependence ◽

Solar Photosphere ◽

The Sun ◽

Solar Cycles ◽

Quasi Biennial Oscillation ◽

Photometric Observations ◽

Cycle 24 ◽

Biennial Oscillation

We study the variability of solar activity using new photospheric proxies originally developed for the analysis of stellar magnetism with the CoRoT and Kepler photometric observations. These proxies were obtained by tracking the temporal modulations in the observations associated with the spots and magnetic features as the Sun rotates. We analyzed 21 yr of observations, spanning solar cycles 23 and 24, collected by the space-based photometric VIRGO and radial velocity GOLF instruments on board the SoHO satellite. We then calculated the photospheric activity proxy Sph is for each of the three VIRGO photometers and the associated Svel proxy from the radial velocity GOLF observations. Comparisons with several standard solar activity proxies sensitive to different layers of the Sun demonstrate that these new activity proxies, Sph and Svel, provide a new manner to monitor solar activity. We show that both the long- and short-term magnetic variabilities respectively associated with the 11-yr cycle and the quasi-biennial oscillation are well monitored, and that the magnetic field interaction between the subsurface, photosphere, and chromosphere of the Sun was modified between Cycle 24 and Cycle 23. Furthermore, the photometric proxies show a wavelength dependence of the response function of the solar photosphere among the three channels of the VIRGO photometers, providing inputs for the study of the stellar magnetism of Sun-like stars.

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Statistical studies of low-power solar flares. Distribution of flares by area, brightness, and classes

Solnechno-Zemnaya Fizika ◽

10.12737/22486 ◽

2017 ◽

Vol 3 (1) ◽

pp. 34-45 ◽

Cited By ~ 3

Author(s):

Александр Боровик ◽

Aleksandr Borovik ◽

Антон Жданов ◽

Anton Zhdanov

Keyword(s):

Low Power ◽

Solar Flares ◽

Software Package ◽

Statistical Data ◽

Correlation Coefficients ◽

Flare Activity ◽

The Sun ◽

Electronic Database ◽

First Results ◽

Statistical Studies

An electronic database has been created for 123801 solar flares that occurred on the Sun over the period from 1972 to 2010. It is based on catalogs of the Solar Geophysical Data (SGD) and Quarterly Bulletin on Solar Activity. A software package has been used for statistical data preprocessing. The first results revealed a number of new features in the distribution of parameters of solar flares, which differ from those obtained previously. We have found that more than 90 % of all solar flares are low-power. The most numerous class comprises SF flares (64 %). Flare activity shows a pronounced cyclicity and high correlation with Wolf numbers. The highest correlation coefficients indicate S and 1 solar flares. There is also a high correlation between individual flare classes: S and 1, 1 and (2–4). The results obtained previously [Mitra et al., 1972] which provide evidence of the prevalence of SN solar flares (47 %) and the existence of significant peaks for SN and 1N flares, have not been confirmed. The distri-bution of the number of solar flares with increasing op-tical importance smoothly decreases without significant deviations. With increasing optical importance, solar flares are gradually redistributed toward an increase in brightness class. The excess of the number of SN and 1N solar flares present in the distributions obtained in [Mitra et al., 1972] are most likely associated with poor statistics.

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