scholarly journals A magnetic cycle ofτBootis? The coronal and chromospheric view

2012 ◽  
Vol 333 (1) ◽  
pp. 26-29 ◽  
Author(s):  
K. Poppenhaeger ◽  
H.M. Günther ◽  
J.H.M.M. Schmitt
Keyword(s):  
Magnetic Cycle

scholarly journals 22 Year Solar Magnetic Cycle and its relation to Convection Zone Dynamics

2018 ◽  
Vol 13 (S340) ◽  
pp. 9-10 ◽  
Author(s):  
Kiran Jain ◽  
Sushanta Tripathy ◽  
Rudolf Komm ◽  
Frank Hill ◽  
Rosaria Simoniello
Keyword(s):  
Convection Zone ◽  
Magnetic Cycle ◽  
Solar Magnetic Cycle ◽  
Local Properties ◽  
Global And Local

AbstractUsing continuous observations for 22 years from ground-based network GONG and space-borne instruments MDI onboard SoHO and HMI onboard SDO, we report both global and local properties of the convection zone and their variations with time.

Chaotic modulation of the solar cycle

1994 ◽  
Vol 348 (1688) ◽  
pp. 445-447 ◽  
Keyword(s):  
Solar Cycle ◽  
Magnetic Fields ◽  
Active Regions ◽  
17Th Century ◽  
Magnetic Activity ◽  
Maunder Minimum ◽  
Magnetic Cycle ◽  
Sunspot Minimum ◽  
Proxy Records ◽  
Oriented Parallel

The Sun’s magnetic activity varies cyclically, with a well-defined mean period of about 11 years. At the beginning of a new cycle, spots appear at latitudes around ±30°; then the zones of activity expand and drift towards the equator, where they die away as the new cycle starts again at higher latitudes. Active regions are typically oriented parallel to the equator, with oppositely directed magnetic fields in leading and following regions. The sense of these fields is opposite in the two hemispheres and reverses at sunspot minimum. So the magnetic cycle has a 22-year period, with waves of activity that drift towards the equator. Sunspot records show that there was a dearth of spots in the late 17th century - the Maunder minimum - which can also be detected in proxy records.

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.

scholarly journals The RoPES project with HARPS and HARPS-N

2018 ◽  
Vol 612 ◽  
pp. A41 ◽  
Author(s):  
A. Suárez Mascareño ◽  
J. I. González Hernández ◽  
R. Rebolo ◽  
S. Velasco ◽  
B. Toledo-Padrón ◽  
...  
Keyword(s):  
Activity Pattern ◽  
Terrestrial Planets ◽  
Magnetic Cycle ◽  
Complex Activity ◽  
Stellar Activity ◽  
Chromospheric Activity ◽  
Analysis Technique ◽  
Short Period ◽  
Orbital Periods ◽  
Modest Level

We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars, which combines radial velocities (RVs) from the HARPS and HARPS-N spectrographs to search for short-period terrestrial planets. HD 176986 b and c are super-Earth planets with masses of 5.74 and 9.18 M⊕, orbital periods of 6.49 and 16.82 days, and distances of 0.063 and 0.119 AU in orbits that are consistent with circular. The host star is a K2.5 dwarf, and despite its modest level of chromospheric activity (log10 (RHK' = –4.90 ± 0.04), it shows a complex activity pattern. Along with the discovery of the planets, we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable for testing the available RV analysis technique and further our understanding of stellar activity.

scholarly journals Cyclic Period Changes in the Algol WW Cygni

2004 ◽  
Vol 194 ◽  
pp. 87-88
Author(s):  
R. T. Zavala ◽  
B. J. McNamara ◽  
T. E. Harrison ◽  
H. Bogue ◽  
H. L. Maness
Keyword(s):  
Orbital Period ◽  
Period Change ◽  
Close Binaries ◽  
Cyclic Change ◽  
Optical Interferometer ◽  
Third Body ◽  
Magnetic Cycle ◽  
Color Changes ◽  
The Third ◽  
Algol System

AbstractYear to decade-long cyclic period changes have been observed in many classes of close binaries. The Algol binary WW Cygni shows a cyclic change in its orbital period with an amplitude of slightly more than 0.02 days and a period of 56 years. A hypothetical third or fourth body does not satisfactorily explain the observed variation in the orbital period. The change in luminosity and color of the system at primary eclipse minimum are in agreement with the model proposed by Applegate for a magnetic cycle induced period change in WW Cygni. We have commenced monitoring 9 close binaries for evidence of the luminosity and color changes consistent with the magnetic cycle hypothesis. δ Librae is suggested as a case suitable for observation with an optical interferometer to test the third body proposed for this Algol system.

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