DECIPHERING SOLAR MAGNETIC ACTIVITY. I. ON THE RELATIONSHIP BETWEEN THE SUNSPOT CYCLE AND THE EVOLUTION OF SMALL MAGNETIC FEATURES

Knowledge of the solar sunspot cycle extends back to the mid-19th century with the work of Schwabe (1843) and Wolf (1856). The mean cycle period of the Sun is 11 years, however, individual cycle lengths range from 7 to 13 years (Eddy 1977). In this century, however, the length of the solar cycle has been closer to 10 years (Donahue and Baliunas 1992a). A complete explanation of the solar magnetic activity and its variations has not yet been produced, although a hydromagnetic dynamo is frequently posited as the source of solar (and therefore stellar) magnetic activity. Empirical measurements of those stars in the H-R Diagram which have convective zones and surface magnetic activity provide the boundary conditions and the range of behavior which must be explained by any all-encompassing theory explaining stellar magnetic activity, and activity cycles.

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Double sunspot-cycle variation in terrestrial magnetic activity, 1884-1963

Journal of Geophysical Research Atmospheres ◽

10.1029/jz071i003p00965 ◽

1966 ◽

Vol 71 (3) ◽

pp. 965-974 ◽

Cited By ~ 67

Author(s):

Edwin J. Chernosky

Keyword(s):

Sunspot Cycle ◽

Magnetic Activity ◽

Cycle Variation

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Relative phase asynchrony and long-range correlation of long-term solar magnetic activity

10.1117/12.2281943 ◽

2017 ◽

Author(s):

Linhua Deng

Keyword(s):

Long Range ◽

Relative Phase ◽

Magnetic Activity ◽

Range Correlation ◽

Solar Magnetic Activity

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‘Sumer’ – Solar Ultraviolet Measurements of Emitted Radiation

International Astronomical Union Colloquium ◽

10.1017/s0252921100026178 ◽

1994 ◽

Vol 144 ◽

pp. 619-624 ◽

Cited By ~ 1

Author(s):

K. Wilhelm ◽

W. Curdt ◽

A. H. Gabriel ◽

M. Grewing ◽

M. C. E. Huber ◽

...

Keyword(s):

Spectral Resolution ◽

Extreme Ultraviolet ◽

Flow Characteristics ◽

Magnetic Activity ◽

High Accuracy ◽

The Sun ◽

Lower Corona ◽

Doppler Shifts ◽

Solar Magnetic Activity ◽

Solar Ultraviolet

AbstractThe experiment Solar Ultraviolet Measurements of Emitted Radiation (SUMER) is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. Specifically, SUMER will measure profiles and intensities of extreme ultraviolet (EUV) lines emitted in the solar atmosphere ranging from the upper chromosphere to the lower corona; determine line broadenings, spectral positions and Doppler shifts with high accuracy; provide stigmatic images of selected areas of the Sun in the EUV with high spatial, temporal and spectral resolution and obtain full images of the Sun and the inner corona in selectable EUV lines, corresponding to a temperature range from 104to more than 1.8 x 106K. The spatial and spectral resolution capabilities of the instrument will be considered in this contribution in some detail, and a new detector concept will be introduced.

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The generation of solar magnetic activity: Photospheric flows and coronal fields

Advances in Space Research ◽

10.1016/0273-1177(93)90451-g ◽

1993 ◽

Vol 13 (9) ◽

pp. 15-22

Author(s):

Gerard Van Hoven

Keyword(s):

Magnetic Activity ◽

Solar Magnetic Activity

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Radio Flare Activity of RS CVn Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900065219 ◽

1980 ◽

Vol 88 ◽

pp. 403-403

Author(s):

Paul A. Feldman

Keyword(s):

Binary Star ◽

Quantitative Model ◽

Magnetic Activity ◽

Flare Activity ◽

Radio Observatory ◽

X Ray ◽

Rs Cvn Stars ◽

Solar Magnetic Activity ◽

Radio Flare ◽

Systematic Program

For several years, a systematic program to observe RS CVn and similar binaries has been undertaken with the 46-m telescope of the Algonquin Radio Observatory. A number of large radio outbursts at 2.8 cm wavelength has been found from HR 1099, AR Lac, SZ Psc, UX Ari, and HR 5110. In several cases, simultaneous, or nearly simultaneous, observations of these stars were made by cooperating observers at (other) radio, optical, UV, and X-ray wavelengths. It is now clearly established that the mechanism responsible for the cm-wavelength radio emission is nonthermal gyrosynchrotron radiation in a volume whose characteristic dimension is comparable with the binary star separation. More generally, a semi-quantitative model for the radio flare activity of these stars seems to be possible using greatly scaled-up analogues of solar magnetic activity.

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Non-axisymmetrical distributions of solar magnetic activity and irradiance

Advances in Space Research ◽

10.1016/s0273-1177(02)00248-x ◽

2002 ◽

Vol 29 (12) ◽

pp. 1941-1946 ◽

Cited By ~ 4

Author(s):

E.E. Benevolenskaya

Keyword(s):

Magnetic Activity ◽

Solar Magnetic Activity

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Magnetic activity in the HARPS M dwarf sample

Astronomy and Astrophysics ◽

10.1051/0004-6361/201527078 ◽

2017 ◽

Vol 600 ◽

pp. A13 ◽

Cited By ~ 59

Author(s):

N. Astudillo-Defru ◽

X. Delfosse ◽

X. Bonfils ◽

T. Forveille ◽

C. Lovis ◽

...

Keyword(s):

Monitoring Program ◽

Rotation Period ◽

Magnetic Activity ◽

Spectral Lines ◽

M Dwarfs ◽

Low Mass Stars ◽

The Galaxy ◽

Low Mass ◽

M Dwarf ◽

The Relationship

Context. Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the Ca ii H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The Ca ii emission is traditionally quantified through the R'HK-index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs – the most numerous stars of the Galaxy – were left out of these analyses and no calibration of their Ca ii H and K emission to an R'HK exists to date. Aims. We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the R'HK-index that extends to the realm of M dwarfs, and by evaluating the relationship between R'HK and the rotation period. Methods. We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the Ca ii H and K lines to a close spectral continuum) into the R'HK. We monitored magnetic activity through the Ca ii H and K emission lines in the HARPS M dwarf sample. Results. The R'HK index, like the fractional X-ray luminosity LX/Lbol, shows a saturated correlation with rotation, with saturation setting in around a ten days rotation period. Above that period, slower rotators show weaker Ca ii activity, as expected. Under that period, the R'HK index saturates to approximately 10-4. Stellar mass modulates the Ca ii activity, with R'HK showing a constant basal activity above 0.6 M⊙ and then decreasing with mass between 0.6 M⊙ and the fully-convective limit of 0.35 M⊙. Short-term variability of the activity correlates with its mean level and stars with higher R'HK indexes show larger R'HK variability, as previously observed for earlier spectral types.

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