Tag Archives: helioseismology

196. Observations of Rossby wave parameter variations during solar cycle 24

Contributed by Mattias Waidele. Posted on September 25, 2023

Equatorial Rossby waves are detected using the HMI’s time-distance subsurface flow fields. It is also found that the power of the Rossby waves show a positive correlation with the sunspot number, while the frequency of the waves shows an anti-correlation with the sunspot number.

189. Spatial Scales and Time Variation of Solar Subsurface Convection

Contributed by Alexander Getling. Posted on October 31, 2022

Spectral analysis of the spatial structure of solar subphotospheric convection is carried out for subsurface flow maps. It is found that the horizontal flow scales increase rapidly with depth, from supergranulation to giant-cell values. The total power of the convective flows is found to be anticorrelated with the sunspot number variation over the solar activity cycle in shallow subsurface layers and positively correlated at larger depths.

188. Constraining Global Solar Models through Helioseismic Analysis

Contributed by Andrey Stejko. Posted on October 28, 2022

Forward modeling is applied to numerous global hydrodynamic solar models, and helioseismic measurements on the meridional circulation are made using the forward modeling results. Comparison against the observational measurements shows significant differences, indicating our insufficient knowledge on either the global hydrodynamic modeling or the helioseismic inversions.

183. Phase shifts measured in evanescent acoustic waves above the solar photosphere and their possible impacts on local helioseismology

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.

157. Forward Modeling Helioseismic Signatures of One- and Two-Cell Meridional Circulation

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.

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.