Tag Archives: solar interior

231. Oscillatory Phase and Acoustic Travel-Time Inconsistencies Measured Between SDO/HMI and GONG Dopplergrams

Contributed by Junwei Zhao. Posted on July 30, 2026

Oscillatory phase shifts were measured between Doppler velocities observed by GONG and HMI at the same locations on the solar disk over a 14-year period. The two datasets exhibit disk-position-dependent phase differences, indicating the presence of phase anomalies that may introduce systematic errors into inferences of the Sun’s meridional circulation and internal rotation.

223. Helioseismic evidence that the solar dynamo originates near the tachocline

Contributed by Krishnendu Mandal. Posted on February 26, 2026

Helioseismic analysis of solar torsional oscillations reveals dynamo-wave–like signatures that originate near the tachocline and propagate through the convection zone, linking internal zonal flows to the surface magnetic cycle. Additional evidence from frequency-splitting coefficients and rotational shear variations shows strong solar-cycle correlations, supporting the tachocline as a primary site of solar dynamo action.

153. Computing Helioseismic Sensitivity Kernels for the Sun’s Large-scale Internal Flows Using Global-scale Wave-propagation Simulations

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.

133. Hemispherical Asymmetry in the Solar Meridional Flow

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.

126. Solar Oblateness and Its Variations in Phase with the 22-yr Magnetic Cycle

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.

107. Cyclic Variations of the Sun’s Seismic Radius

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.

17. Is the recent discovery of the multi-cell meridional circulation a threat to the flux-transport dynamo?

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.