scholarly journals Joint Discussion 8 Solar and stellar activity cycles

2006 ◽  
Vol 2 (14) ◽  
pp. 271-272
Author(s):  
Alexander G. Kosovichev ◽  
Klaus G. Strassmeier
Keyword(s):  
Magnetic Field ◽  
Time Scales ◽  
Tree Ring ◽  
Solar Magnetic Field ◽  
Sunspot Cycle ◽  
Magnetic Cycle ◽  
Stellar Activity ◽  
Tree Ring Data ◽  
Activity Cycles

The solar magnetic field and its associated atmospheric activity exhibits periodic variations on a number of time scales. The 11-year sunspot cycle and its underlying 22-year magnetic cycle are, besides the 5-minute oscillation, the most widely known. Amplitudes and periods range from a few parts per million (ppm) and 2–3 minutes for p-modes in sunspots, a few 10 ppm and 10 minutes for the granulation turn around, a few 100 ppm and weeks for the lifetime of plages and faculae, 1000 ppm and 27 days for the rotational signal from spots, to the long-term cycles of 90 yr (Gleissberg cycle), 200 - 300 yr (Wolf, Spörer, Maunder minima), 2,400 yr from 14C tree-ring data, and possibly in excess of 100,000 yr.

scholarly journals About long term modulation of cosmic rays in the 23-24 solar activity cycles

2021 ◽  
pp. 23-29
Author(s):  
Anatoly V. Belov ◽  
Raisa T. Gushchina ◽  
Victor Yanke
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
The Sun ◽  
Model Calculations ◽  
Activity Cycles ◽  
The Magnetic Field ◽  
Solar Activity Cycles

Recently, there has been a significant trend in magnetic fields on the Sun. The total magnetic field of the Sun from the end of the 22nd cycle of solar activity (SA) has more than halved and this decrease continues. Chan- ges in the magnetic field are the key to all the active phenomena occurring on the Sun and in the heliosphere and, accordingly, to processes in cosmic rays. In long-term CR variations in 23-24 cycles of SA the attenuation of the solar magnetic field is displayed and these variations turned out to be the smallest for the entire time of CR observations. Model calculations of CR modulation for 21-22 and 23-24 cycles of SA showed: with a slight difference in the regression characteristics obtained, the distribution of contributions to the generated CR modulation from the effects of various SA indices is strongly varies in the analyzed periods. Possible reasons for the features of the last two CA cycles are discussed.

A Clock in the Sun?

2019 ◽  
Vol 15 (S354) ◽  
pp. 127-133
Author(s):  
C. T. Russell ◽  
J. G. Luhmann ◽  
L. K. Jian
Keyword(s):  
Sunspot Number ◽  
Solar Minimum ◽  
Sunspot Cycle ◽  
Solar Dynamo ◽  
The Sun ◽  
Average Period ◽  
Magnetic Cycle ◽  
Number Cycle ◽  
As If

AbstractThe sunspot cycle is quite variable in duration and amplitude, yet in the long term, it seems to return to solar minimum on schedule, as if guided by a clock with an average period of close to 11.05 years for the sunspot number cycle and 22.1 years for the magnetic cycle. This paper provides a brief review of the sunspot number cycle since 1750, discusses some of the processes controlling the solar dynamo, and provides clues that may add to our understanding of what controls the cadence of the solar clock.

Regression Model for the 22-year Hale Solar Cycle Derived from High Altitude Tree-ring Data

1994 ◽  
Vol 11 (2) ◽  
pp. 157-163 ◽  
Author(s):  
J. O. Murphy ◽  
H. Sampson ◽  
T. T. Veblen ◽  
R. Villalba
Keyword(s):  
Solar Cycle ◽  
Regression Model ◽  
High Altitude ◽  
Tree Ring ◽  
Magnetic Cycle ◽  
Tree Ring Data ◽  
Highly Correlated ◽  
Successive Maximum ◽  
Index Time Series ◽  
Past 300 Years

AbstractInitially some simple analytical properties based on the annual Zürich relative sunspot number are established for the 22-year Hale solar magnetic cycle. Since about AD1850, successive maximum sunspot numbers in a Hale cycle are highly correlated. Also, a regression model for the reconstruction of the 22-year Hale cycle has been formulated from proxy tree-ring data, obtained from spruce trees growing at a high altitude site in White River National Forest in Colorado. Over a considerable fraction of the past 300 years to AD1986, the ring-index time series power spectrum exhibits a strong 22-year periodicity, and more recently a significant spectral peak (at the 95% confidence level) at approximately 11 years. The model shows that the greatest variation in ‘amplitude’ in the magnetic cycle occurs over the early decades of the eighteenth century, when the sample size is small. Thereafter, a nearly constant amplitude is maintained until about AD1880 when a break occurs in both phase correspondence and amplitude, extending over the next three cycles. From AD1950 the signal recovers phase with the solar cycle, with reduced but increasing amplitude.

scholarly journals Wavelet analysis of long-term variations in neutron monitor, sunspot number and interplanetary magnetic field data

2021 ◽  
pp. 39-42
Author(s):  
Fraser Baird ◽  
Alexander MacKinnon
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Solar Magnetic Field ◽  
Cosmic Ray ◽  
Negative Polarity ◽  
Neutron Monitors ◽  
Magnetic Field Data ◽  
First Time ◽  
Long Term Variations

For the first time, based on the experimental data of AMS-02, a three-parameter spectrum of variations of ga - lactic cosmic rays was obtained in the range of rigidity 1- 20 GV, to which neutron monitors are most sensitive. It was found that during the period of negative polarity of the solar magnetic field, a power-law spectrum of va - riations is observed with a strong exponential decay in the region of high rigidity. When the polarity changes to positive at the beginning of the new 24th solar cycle, the spectrum of cosmic ray variations becomes purely po- wer-law. The transition to the experimentally obtained spectrum of variations will make it possible to remove a number of uncertainties and increase the accuracy of the analysis of data from the ground network of detectors. This will make it possible to retrospectively obtain fluxes of galactic protons with an average monthly resolution for the period of the space era based on ground-based monitoring.

scholarly journals The Mount Wilson Program for Stellar Activity Cycles

1983 ◽  
Vol 102 ◽  
pp. 113-132
Author(s):  
Arthur H. Vaughan
Keyword(s):  
Stellar Mass ◽  
Present Review ◽  
Current Evidence ◽  
Stellar Activity ◽  
Activity Cycles

The present review will focus upon the incidence, form, and characteristic timescale of long-term chromospheric variations that, from the work of O.C. Wilson and his successors, can be descerned in records of CaII H and K emission now extending over 16 years, and the relation, if any, between properties of activity cycles and stellar mass, age, and rate of rotation, in the light of current evidence.

scholarly journals HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

2018 ◽  
Vol 620 ◽  
pp. A34 ◽  
Author(s):  
M. Flores ◽  
J. F. González ◽  
M. Jaque Arancibia ◽  
C. Saffe ◽  
A. Buccino ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Activity Cycle ◽  
Earth Planet ◽  
Stellar Activity ◽  
Balmer Lines ◽  
Solar Type ◽  
Activity Cycles ◽  
Novel Strategy ◽  
Solar Type Star

Context. The detection of chromospheric activity cycles in solar-analogue and twin stars can be used to place the solar cycle in a wider context. However, relatively few of these stars with activity cycles have been detected. It is well known that the cores of the Ca II H&K lines are modulated by stellar activity. The behaviour of the Balmer and other optical lines with stellar activity is not yet completely understood. Aims. We search for variations in the Ca II H&K, Balmer, and Fe II lines modulated by stellar activity. In particular, we apply a novel strategy to detect possible shape variations in the Hα line. Methods. We analysed activity signatures in HD 38858 using HARPS and CASLEO spectra obtained between 2003 and 2017. We calculated the Mount Wilson index (SMW), log(R′HK), and the statistical moments of the Ca II H&K, Balmer, and other optical lines. We searched for periodicities using the generalized Lomb-Scargle periodogram. Results. We detect a long-term activity cycle of 10.8 yr in Ca II H&K and Hα in the solar-analogue star HD 38858. In contrast, this cycle is marginally detected in the Fe II lines. We also detect a noticeable variation in radial velocity that seems to be produced by stellar activity. Conclusions. HD 38858 is the second solar-analogue star where we find a clear activity cycle that is replicated in the Balmer lines. Spectral indexes based on the shape of Hα line seem to be more reliable than the fluxes in the same line for detecting activity variations. The cyclic modulation we detected gives place to a variation in radial velocity that previously has been associated with a super-Earth planet. Finally, due to the similarity of HD 38858 with the Sun, we recommend to continue monitoring this star.

The large-scale solar magnetic field and 11-year activity cycles

2000 ◽  
Vol 44 (11) ◽  
pp. 759-764 ◽  
Author(s):  
V. I. Makarov ◽  
A. G. Tlatov
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Activity Cycles

scholarly journals Stellar Activity and Calcium Emission Variability

1983 ◽  
Vol 71 ◽  
pp. 195-199
Author(s):  
Sallie L. Baliunas
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Magnetic Activity ◽  
Small Scale ◽  
Physical Parameters ◽  
Stellar Activity ◽  
Ongoing Work ◽  
Chromospheric Emission ◽  
Activity Cycles

ABSTRACT.Time series analysis of fluctuations of Ca II H and K chromospheric emission has provided us with much information concerning stellar activity. On all timescales, events which parallel solar behavior can be observed: activity cycles, on timescales of years; rotation of stars and evolution of active areas on timescales of days to weeks; flare-like phenomena on timescales as short as minutes.We expect that the analogues of solar activity exist on other stars . By studying stellar counterparts to solar activity, we can hope to investigate the physical parameters which are thought to influence chromospheric and coronal activity. The stellar surfaces are usually spatially unresolvable; it is thus difficult to measure directly either small-scale surface inhomogeneities or the associated magnetic fields expected from spatially restricted areas.On the Sun, however, areas with strong surface magnetic fields show intense chromospheric Ca II H and K emission (Babcock and Babcock 1955; Skumanich et al 1975). Although indirect, the Ca II H and K features are good indicators of stellar magnetic activity. A major advantage of the Ca II features is their accessibility to ground-based observatories. Long-term synoptic programs are in progress to monitor stellar chromospheric activity, and this paper will highlight ongoing work at Mt. Wilson. Monitoring variations of Ca II H and K chromospheric emission over different timescales can reveal different physical phenomena: (1) Long-term (years) variations corresponding to stellar activity cycles; (2) intermediate term (days-months) variations indicating rotation or evolution of stellar active areas; (3) short-term (minutes-hours) variations resulting from impulsive and flare-like phenomena.

Long-term stellar magnetic field study at the Crimean Astrophysical Observatory

2018 ◽  
Vol 13 (S340) ◽  
pp. 35-38
Author(s):  
Varvara Butkovskaya ◽  
Sergei Plachinda ◽  
Dilyara Baklanova
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Study ◽  
Crimean Astrophysical Observatory ◽  
Activity Cycles ◽  
Magnetic Cycles ◽  
Long Term Monitoring ◽  
The Magnetic Field ◽  
Term Monitoring

AbstractThe long-term monitoring of magnetic cycles is a key diagnostic in understanding how dynamo generation and amplification of magnetic fields occur in solar-like stars. One of the current key problems is the establishment of the magnetic field behavior during the activity cycles for stars of different ages and evolutionary statuses. We present the experience of using own long-term datasets for study of activity cycles in selected stars at the Crimean Astrophysical Observatory.

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