Contributed by Chris Hanson. Posted on June 27, 2022
High-frequency inertial waves were detected inside the Sun, propagating retrograde relative to the solar rotation with a phase speed faster than equatorial Rossby waves. How these waves are generated is discussed but remains unclear.
Contributed by Fadil Inceoglu. Posted on November 3, 2021
Quasi-biennial oscillations are found in the Sun’s interior rotation-rate residuals. They appear differently at different depths and latitudes, and evolve with time.
Contributed by Junwei Zhao. Posted on March 28, 2021
A new method to derive the helioseismic sensitivity kernels for the Sun’s large-scale internal flows is developed. The new method is based on the idea of placing a small-volume flow perturbation inside the Sun’s model, simulating the wavefield in the photosphere, and then measuring the phase shifts caused by this internal perturbation.
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 Kyuhyoun Cho. Posted on September 28, 2019
What excites the sunspot umbral oscillations? Through analyzing two sunspots observed by FeI line, the authors found that the 3-minute umbral oscillations are likely excited by internal small-scale magnetoconvection associated with umbral dots.
Contributed by Abdanour Irbah. Posted on June 18, 2019
The Sun’s oblateness shows a variation with solar cycles, in phase with the solar activity level in Cycle 23 but in anti-phase with the activity level in Cycle 24. Such a trend of in-phase during odd cycles and anti-phase during even cycles is confirmed after examining past observations.
Contributed by Alexander Kosovichev. Posted on July 30, 2018
The Sun’s seismic radius, measured from the frequencies of f modes, is determined using both MDI and HMI data, covering a total of 21 years. It is found that the seismic radius is reduced by 1-2 km during the maxima, but the largest change of the radius happens at about 5 Mm beneath the surface.
Contributed by Bidya Binay Karak. Posted on May 27, 2014
Motivated by recent observations we have explored whether the flux-transport dynamo model can work with multi-cell meridional flow. We find that it can work when certain conditions are fulfilled.
Contributed by Tom Duvall. Posted on April 29, 2014
Analysis of a large number of supergranules observed with HMI and simulations with a convectively stabilized solar model imply that the average supergranular cell has a peak upflow of 240 m s-1 at a depth of 2.3 Mm and a corresponding peak outward horizontal flow of 700 m s-1 at a depth of 1.6 Mm.
Contributed by Mausumi Dikpati. Posted on February 11, 2014
Solar meridional circulation, if mechanically driven and thermally
braked, contains two cells in latitude; generating two cells in depth,
recently observed by SDO/HMI, is a new challenge to theory.