E-Print Archive

There are 3914 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Solar Cycle Variations of Rotation and Asphericity in the Near-Surface Shear Layer View all abstracts by submitter

Alexander Kosovichev   Submitted: 2018-05-25 11:55

The precise shape of the Sun is sensitive to the influence of gravity, differential rotation, local turbulence and magnetic fields. It has been previously shown that the solar shape exhibits asphericity that evolves with the 11-year cycle. Thanks to the capability of the SoHO/MDI and SDO/HMI instruments to observe with an unprecedented accuracy the surface gravity oscillation (f) modes, it is possible to extract information concerning the coefficients of rotational frequency splitting, a1, a3 and a5, that measure the differential rotation, together with the a2, a4 and a6 asphericity coefficients. Analysis of these helioseismology data for almost two solar cycles, from 1996 to 2017, reveals a close correlation of the a1 and a5 coefficients with the solar activity, whilst a3 exhibits a long-term trend and a weak correlation in the current cycle indicating a substantial change of the global rotation, potentially associated with a long-term evolution of the solar cycles. Looking in more details, the asphericity coefficients, a2, a4 and a6 are more strongly associated with the solar cycle when applying a time lag of respectively 0.1, 1.6 and -1.6 years. The magnitude of a6-coefficient varies in phase with the sunspot number (SN), but its amplitude is ahead of the SN variation. The last measurements made in mid 2017 indicate that the magnitude of a6-coefficient has probably reached its minimum; therefore, the next solar minimum can be expected by the end of 2018 or in the beginning of 2019. The so-called seismic radius in the range of f-mode angular degree: l=137-299 exhibits a temporal variability in anti-phase with the solar activity; its relative value decreased by 2.3E-05 in Solar Cycle 23 and 1.7E-05 in Cycle 24. Such results will be useful for better understanding the physical mechanisms which act inside the Sun, and so, better constrain dynamo models for forecasting the solar cycles

Authors: A. G. Kosovichev, J. -P. Rozelot
Projects: SDO-HMI,SoHO-MDI

Publication Status: to appear in Journal of Atmospheric and Solar-Terrestrial Physics (JASTP)
Last Modified: 2018-05-26 17:25
Go to main E-Print page  Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017   Solar coronal loop dynamics near the null point above active region NOAA 2666  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Linear Polarization Features in the Quiet-Sun Photosphere: Structure and Dynamics
Solar Microflares Observed by SphinX and RHESSI
Two Kinds of Dynamic Behavior in a Quiescent Prominence Observed by the NVST
Resistively-limited current sheet implosions in planar anti-parallel (1D) and null-point containing (2D) magnetic field geometries
Is It Small-scale Weak Magnetic Activity That Effectively Heats the Upper Solar Atmosphere?
Self-Similar Approach for Rotating Magnetohydrodynamic Solar and Astrophysical Structures
Spectroscopic and imaging observations of small-scale reconnection events
A Study of Magnetic Field Characteristics of Flaring Active Region Based on Nonlinear Force-free Field Extrapolation
A Study of a Compound Solar Eruption with Two Consecutive Erupting Magnetic Structures
Non-potential magnetic helicity ratios at the onset of eruptions
Solar Cycle Observations of the Neon Abundance in the Sun-as-a-star
Subresolution Activity in Solar and Stellar Coronae from Magnetic Field Line Tangling
A Model of Zebra Patterns in Solar Radio Emission
Three-dimensional magnetic reconnection in a collapsing coronal loop system
On the Synthesis of GOES Light Curves from Numerical Models
Efficient Calculation of Non-Local Thermodynamic Equilibrium Effects in Multithreaded Hydrodynamic Simulations of Solar Flares
2D solar wind speeds from 6 to 26 solar radii in solar cycle 24 by using Fourier filtering
Non-damping oscillations at flaring loops
An Event-Based Verification Scheme for the Real-Time Flare Detection System at Kanzelhöhe Observatory
Computation of Relative Magnetic Helicity in Spherical Coordinates

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2003 Solar Physics Group - Montana State University