Category Archives: Helioseismology

155. Hydrodynamic Properties of the Sun’s Giant Polar Vortices

Contributed by David H. Hathaway. Posted on April 6, 2021

The giant cellular flows, obtained through tracking HMI-observed Dopplergrams, are used to estimate kinetic helicity and Reynolds stress inside the Sun, as well as differential rotation and poleward drift near the bottom of the convection zone.

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.

152. Probing the Solar Meridional Circulation using Fourier Legendre Decomposition

Contributed by Doug Braun. Posted on March 16, 2021

Fourier Legendre decomposition is applied on HMI’s long-term Doppler-velocity observations to derive the Sun’s internal meridional circulation. In addition to the well-known center-to-limb effect, a non-axisymmetric component in the northern- and southern-hemisphere is identified as another systematic effect that complicates the derivation of the internal meridional circulation.

150. Photospheric Oscillations in and around Active Region 11158, including the Polarity Inversion Line

Contributed by Aimee Norton. Posted on January 20, 2021

To search for signatures of Alfvénic waves in the solar photosphere, the authors analyze the oscillation amplitudes, phases and time-distance behavior between different observables in a sunspot umbra, its polarity inversion line, and surrounding area.

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.