scholarly journals An Estimation of Global p-mode Frequencies and Splittings from the IRIS Network Data: 1989–1996

2001 ◽  
Vol 203 ◽  
pp. 97-100 ◽  
Author(s):  
Sh. A. Ehgamberdiev ◽  
A. V. Serebryanskiy ◽  
Sh. S. Khalikov ◽  
E. Fossat ◽  
B. Gelly ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Activity Cycle ◽  
Data Bank ◽  
Magnetic Activity ◽  
Network Data ◽  
Frequency Table ◽  
Solar Magnetic Activity ◽  
Iris Data

The IRIS network has accumulated low-l p-modes data since July, 1989, i.e. one complete solar cycle. Since the last publication of a frequency table (Gelly et al. 1997) the IRIS data bank was not only filled with new data, but also has been supplemented with data from other helioseismology instruments, through cooperative programs. The results of a new estimations of frequencies and splitting obtained from IRIS++ data (Gelly et al. 1998) for period 1989-1996, as well as their variation along the solar magnetic activity cycle are presented.

scholarly journals Solar-cycle irradiance variations over the last four billion years

2020 ◽  
Vol 636 ◽  
pp. A83 ◽  
Author(s):  
Anna V. Shapiro ◽  
Alexander I. Shapiro ◽  
Laurent Gizon ◽  
Natalie A. Krivova ◽  
Sami K. Solanki
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Solar Irradiance ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Magnetic Activity ◽  
The Sun ◽  
Earth’S Atmosphere ◽  
Solar Magnetic Activity ◽  
Earth's Atmosphere

Context. The variability of the spectral solar irradiance (SSI) over the course of the 11-year solar cycle is one of the manifestations of solar magnetic activity. There is strong evidence that the SSI variability has an effect on the Earth’s atmosphere. The faster rotation of the Sun in the past lead to a more vigorous action of solar dynamo and thus potentially to larger amplitude of the SSI variability on the timescale of the solar activity cycle. This could lead to a stronger response of the Earth’s atmosphere as well as other solar system planets’ atmospheres to the solar activity cycle. Aims. We calculate the amplitude of the SSI and total solar irradiance (TSI) variability over the course of the solar activity cycle as a function of solar age. Methods. We employed the relationship between the stellar magnetic activity and the age based on observations of solar twins. Using this relation, we reconstructed solar magnetic activity and the corresponding solar disk area coverages by magnetic features (i.e., spots and faculae) over the last four billion years. These disk coverages were then used to calculate the amplitude of the solar-cycle SSI variability as a function of wavelength and solar age. Results. Our calculations show that the young Sun was significantly more variable than the present Sun. The amplitude of the solar-cycle TSI variability of the 600 Myr old Sun was about ten times larger than that of the present Sun. Furthermore, the variability of the young Sun was spot-dominated (the Sun being brighter at the activity minimum than in the maximum), that is, the Sun was overall brighter at activity minima than at maxima. The amplitude of the TSI variability decreased with solar age until it reached a minimum value at 2.8 Gyr. After this point, the TSI variability is faculae-dominated (the Sun is brighter at the activity maximum) and its amplitude increases with age.

scholarly journals The future of helioseismology

2009 ◽  
Vol 5 (H15) ◽  
pp. 352-353
Author(s):  
Alexander G. Kosovichev
Keyword(s):  
Solar Cycle ◽  
Physical Properties ◽  
Active Regions ◽  
Magnetic Activity ◽  
Solar Dynamo ◽  
Current Status ◽  
The Sun ◽  
Interior Structure ◽  
Structure And Dynamics ◽  
Solar Magnetic Activity

AbstractHelioseismology has provided us with the unique knowledge of the interior structure and dynamics of the Sun, and the variations with the solar cycle. However, the basic mechanisms of solar magnetic activity, formation of sunspots and active regions are still unknown. Determining the physical properties of the solar dynamo, detecting emerging active regions and observing the subsurface dynamics of sunspots are among the most important and challenging problems. The current status and perspectives of helioseismology are briefly discussed.

scholarly journals What can the annual 10Be solar activity reconstructions tell us about historic space weather?

2018 ◽  
Vol 8 ◽  
pp. A23 ◽  
Author(s):  
Luke Barnard ◽  
Ken G. McCracken ◽  
Mat J. Owens ◽  
Mike Lockwood
Keyword(s):  
Solar Cycle ◽  
Space Weather ◽  
Geomagnetic Storms ◽  
Solar Energetic Particle ◽  
Ground Level ◽  
Magnetic Activity ◽  
Cycle Phase ◽  
Large Space ◽  
Weather Events ◽  
Solar Magnetic Activity

Context: Cosmogenic isotopes provide useful estimates of past solar magnetic activity, constraining past space climate with reasonable uncertainty. Much less is known about past space weather conditions. Recent advances in the analysis of 10Be by McCracken & Beer (2015, Sol Phys 290: 305–3069) (MB15) suggest that annually resolved 10Be can be significantly affected by solar energetic particle (SEP) fluxes. This poses a problem, and presents an opportunity, as the accurate quantification of past solar magnetic activity requires the SEP effects to be determined and isolated, whilst doing so might provide a valuable record of past SEP fluxes. Aims: We compare the MB15 reconstruction of the heliospheric magnetic field (HMF), with two independent estimates of the HMF derived from sunspot records and geomagnetic variability. We aim to quantify the differences between the HMF reconstructions, and speculate on the origin of these differences. We test whether the differences between the reconstructions appear to depend on known significant space weather events. Methods: We analyse the distributions of the differences between the HMF reconstructions. We consider how the differences vary as a function of solar cycle phase, and, using a Kolmogorov-Smirnov test, we compare the distributions under the two conditions of whether or not large space weather events were known to have occurred. Results: We find that the MB15 reconstructions are generally marginally smaller in magnitude than the sunspot and geomagnetic HMF reconstructions. This bias varies as a function of solar cycle phase, and is largest in the declining phase of the solar cycle. We find that MB15's excision of the years with very large ground level enhancement (GLE) improves the agreement of the 10Be HMF estimate with the sunspot and geomagnetic reconstructions. We find no statistical evidence that GLEs, in general, affect the MB15 reconstruction, but this analysis is limited by having too few samples. We do find evidence that the MB15 reconstructions appear statistically different in years with great geomagnetic storms.

scholarly journals Deciphering Solar Magnetic Activity: 140 Years Of The ‘Extended Solar Cycle’ – Mapping the Hale Cycle

2021 ◽  
Author(s):  
Scott William McIntosh ◽  
Robert J Leamon ◽  
Ricky Egeland ◽  
Mausumi Dikpati ◽  
Richard C Altrock ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Magnetic Activity ◽  
Magnetic Cycle ◽  
Fundamental Feature ◽  
Superposed Epoch Analysis ◽  
Consistent Picture ◽  
Solar Magnetic Activity ◽  
Epoch Analysis ◽  
Observational Record ◽  
Sunspot Record

Abstract We investigate the occurrence of the ``extended solar cycle'' (ESC) as it occurs in a host observational data spanning 140 years. Investigating coronal, chromospheric, photospheric and interior diagnostics we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) using previously identified Hale cycle termination events as the key time for the SEA. Our analysis shows that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same SEA method to the sunspot record confirms that Maunder's butterfly pattern is a subset of the underlying Hale cycle, strongly suggesting that the production of sunspots is not the fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern highlights the importance of 55\degree\ latitude in the evolution, and possible production, of solar magnetism.

scholarly journals Modelling solar cycle length based on Poincaré maps for Lorenz-type equations

2010 ◽  
Vol 28 (4) ◽  
pp. 993-1002 ◽  
Author(s):  
H. Lundstedt ◽  
T. Persson
Keyword(s):  
Dynamical Systems ◽  
Solar Cycle ◽  
Dynamic System ◽  
Cycle Length ◽  
Fractal Structure ◽  
Magnetic Activity ◽  
Long Tail ◽  
Solar Magnetic Activity ◽  
General Relations ◽  
Solar Cycle Length

Abstract. Two systems of Lorenz-type equations modelling solar magnetic activity are studied: Firstly a low order dynamic system in which the toroidal and poloidal fields are represented by x- and y-coordinates respectively, and the hydrodynamical information is given by the z coordinate. Secondly a complex generalization of the three ordinary differential equations studied by Lorenz. By studying the Poincaré map we give numerical evidence that the flow has an attractor with fractal structure. The period is defined as the time needed for a point on a hyperplane to return to the hyperplane again. The periods are distributed in an interval. For large values of the Dynamo number there is a long tail toward long periods and other interesting comet-like features. These general relations found for periods can further be physically interpreted with improved helioseismic estimates of the parameters used by the dynamical systems. Solar Dynamic Observatory is expected to offer such improved measurements.

scholarly journals Spatial distribution of quasi-biennial oscillations in high-latitude solar activity

2020 ◽  
Vol 494 (4) ◽  
pp. 4930-4938 ◽  
Author(s):  
L H Deng ◽  
Y Fei ◽  
H Deng ◽  
Y Mei ◽  
F Wang
Keyword(s):  
Spatial Distribution ◽  
Activity Cycle ◽  
Magnetic Activity ◽  
Time Interval ◽  
High Latitudes ◽  
Time Frequency ◽  
Analysis Technique ◽  
Solar Magnetic Activity ◽  
Main Components ◽  
Schwabe Cycle

ABSTRACT Quasi-biennial oscillations (QBOs) are considered to be a fundamental mode of solar magnetic activity at low latitudes (≤50°). However, the evolutionary aspect and the hemispheric distribution of solar QBOs at high latitudes (≥60°) are rarely studied. Here, we apply a relatively novel time-frequency analysis technique, called the synchrosqueezed wavelet transform, in order to extract the main components of the polar faculae in the Northern and Southern hemispheres for the time interval from 1951 August to 1998 December. We note the following. (i) Apart from the 22-yr Hale cycle, the 17-yr extended activity cycle and the 11-yr Schwabe cycle, QBOs have been estimated as a prominent time-scale of solar magnetic activity at high latitudes. (ii) The QBOs of the polar faculae are coherent in the two hemispheres, but the temporal (phase) and the spatial (amplitude) variations of solar QBOs occur unevenly on both hemispheres. (iii) For the 11-yr period mode, this begins in the Northern hemisphere three months earlier than in the Southern hemisphere. Moreover, the spatial and temporal distributions of the hemispheric QBOs differ from those of the 11-yr Schwabe cycle mode in the two hemispheres. Our findings could be helpful to improve our knowledge of the physical origin of the spatial distribution of solar QBOs at high latitudes, and could also provide more constraints on solar dynamo models introduced to characterize the different components of the solar magnetic activity cycle.

scholarly journals C I 5380 Å: A SPECTRAL LINE WITH LOW INFLUENCE FROM STARSPOTS DYNAMICS AND MAGNETIC CYCLES

2012 ◽  
Vol 18 ◽  
pp. 178-181
Author(s):  
D. SOUTO ◽  
J. D. DO NASCIMENTO
Keyword(s):  
Radial Velocity ◽  
Activity Cycle ◽  
Magnetic Activity ◽  
Spectral Lines ◽  
The Sun ◽  
Total Irradiance ◽  
Modulation Signal ◽  
Solar Magnetic Activity ◽  
Activity Cycles ◽  
Magnetic Cycles

In the Sun-as-a-star Project, the sun was observed spectroscopically and photometrically for more than 25 years in order to determine variability and luminosity changes. This project detected systematic longterm decrease in the total irradiance as a consequence of the solar magnetic activity cycle (scale of years) and variability on solar activity from a time scale of days-months. The solar magnetic activity cycles could mimic the radial velocity modulation signal of a long-period companion in several spectral lines. This effect is an important limitation for the exoplanet searches programs using the radial velocity technique. The Lomb-Scargle periodogram analysis of the Sun-as-a-star spectroscopic data shows that the photospheric line C I 5380 Å and other 11 lines seems to not show significant influence from the rotational or cromospheric magnetic activity modulation. Thus, our analysis suggest that C I 5380 Å line could be used in programs that require extremely line stability.

scholarly journals The variations of solar magnetic networks over the solar cycle 23

2012 ◽  
Vol 8 (S294) ◽  
pp. 151-152
Author(s):  
Chong Huang ◽  
Yihua Yan ◽  
Yuanyong Deng ◽  
Yin Zhang ◽  
Baolin Tan ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Solar Cycle ◽  
Magnetic Activity ◽  
Watershed Algorithm ◽  
Heliospheric Observatory ◽  
Solar Cycle 23 ◽  
Solar Magnetic Activity ◽  
Doppler Interferometer

AbstractThis work analyzed the morphologic properties of magnetic networks during Carrington Rotations (CRs) 1955 to 2091 by applying the watershed algorithm to magnetograms observed by the Michelson Doppler Interferometer on board the Solar and Heliospheric Observatory spacecraft. We found that the magnetic networks are of fractal and the average fractal dimension is Df=1.253±0.011. We also find that both the fractal dimension and the size of magnetic networks are anti-correlated with the solar magnetic activity.

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