Contributed by Junwei Zhao. Posted on July 31, 2022
Analysis on high-spectral resolution data shows that oscillations in the higher atmosphere lead those in the lower atmosphere by an order of 1 s when their frequencies are below about 3.0 mHz, and lags behind by about 1 s when their frequencies are above 3.0 mHz. These phase shifts in the evanescent waves pose great challenges to the interpretation of some local helioseismic measurements that involve data acquired at different atmospheric heights.
Contributed by Sushant Mahajan. Posted on September 29, 2021
A time variable center-to-limb effect in photospheric velocity measurements through local correlation tracking is identified, and a robust methodology to correct for it is developed.
Contributed by Andrey M. Stejko. Posted on May 24, 2021
Helioseismic wavefields are simulated using different meridional-circulation models. Time-distance helioseismic measurements applied on the simulated data indicate that it may be difficult to distinguish between single- or double-cell meridional circulation profiles.
Contributed by B. Lekshmi. Posted on October 28, 2019
Subsurface meridional flows from ring-diagram analysis showed a clear hemispheric asymmetry in last 18 years. Interestingly, this flow asymmetry leads the magnetic flux and sunspot number asymmetry by 3.1 – 3.6 years.
Contributed by Chia-Hsien Lin. Posted on May 18, 2018
Meridional flows during the solar minimum and maximum years are derived using 14 years of SOHO/MDI data. The flows changed significantly from the minimum to the maximum, and major changes were associated with the active latitudes.
Contributed by Valery Pipin. Posted on March 19, 2018
It is demonstrated that when taking into account of the radial inhomogeneity of the Coriolis number, the solar-like differential rotation and the double-cell meridional circulation can both be reproduced by the mean-field model.
Contributed by Simon Wing. Posted on March 15, 2018
Various observable, such as polar field, meridional flow, and sunspot number, are examined to identify information flow, causality, and time delay between them during solar cycles. It is expected that this analysis can provide observational constraints on solar cycle models and theories.
Contributed by Ruizhu Chen. Posted on February 27, 2018
The systematic Center-to-Limb effect in time-distance helioseismic measurements is found to be significantly frequency dependent. The dependence further varies with disk-centric distance but not with travel distance.
Contributed by Gopal Hazra. Posted on December 19, 2017
The Sun’s meridional flow varies with the solar cycle, and this is possibly caused by the back-reaction of the dynamo-generated magnetic field on the meridional flow due to the Lorentz force.
Contributed by Derek Lamb. Posted on May 22, 2017
A new method tracking individual features in a long time series of magnetograms yields new measurements of solar differential rotation and meridional circulation rate.