Category Archives: Helioseismology

27. Anomalously Weak Convection on Large Scales in the Sun

Contributed by Shravan Hanasoge. Posted on September 23, 2014

Observed seismic upper bounds on large-scale lateral (horizontal) convective-velocity amplitudes in the solar interior at the depth r/R = 0.96 do not agree with modeling results derived at a similar depth from global convection simulations. The observations of low convective-velocity amplitudes throw into question our understanding of thermal and angular momentum transport in the Sun.

26. SDO/HMI Multi-height Dopplergrams

Contributed by Kaori Nagashima. Posted on August 15, 2014

Multi-height Doppler velocity maps from two layers separated by 50 km are obtained from combinations of currently recorded HMI filtergrams. Using synthetic data of spectral line profiles produced in a convective environment, we test the ability to recover vertical velocity fields at different heights.

24. Solar and stellar differential rotation and dynamo, mean-field vs. global models

Contributed by Gustavo Guerrero. Posted on July 30, 2014

Numerical simulations of solar rotation and dynamo have been performed over the last decades with the aim of understanding the physics of the solar interior.  Here we briefly discuss two main approaches, namely, mean-field modeling and global simulations. We also present recent results of hydrodynamic global simulations which reveal interesting aspects of stellar rotation.

20. Solar Meridional Flow in the Shallow Interior during the Rising Phase of Cycle 24

Contributed by Junwei Zhao. Posted on June 18, 2014

Subsurface meridional flow speed shows an anti-correlation with the magnetic flux being transported poleward above the latitude of 35&#176. In the lower latitude, the residual meridional flow, after a long-time mean profile is subtracted, shows converging flow toward the activity belts.

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.

12. Analyzing 60,000 Supergranules to Determine their Subsurface Flow Profile

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.