A Spherical Harmonic Decomposition Technique for Analysing Steady Photospheric Flows
Abstract
Steady flows in the photosphere, including differential rotation, meridional circulation and convection, can be represented by a spectrum of modes. A technique is described in which the spherical harmonic functions are used to determine the characteristics of this spectrum and the nature of these flows. Some information about the spectrum is lost because only one hemisphere is seen, only the line of sight velocity is measured and the measurements contain noise. This produces an apparent mixing between spectral modes. By analysing synthetic data it is found that, in spite of this mixing, differential rotation can be accurately measured, meridional circulations with small amplitudes can be extracted from the data and giant cells might be separated from supergranules.
- Publication:
-
The Internal Solar Angular Velocity
- Pub Date:
- 1987
- DOI:
- 10.1007/978-94-009-3903-5_16
- Bibcode:
- 1987ASSL..137..115H
- Keywords:
-
- Harmonic Functions;
- Photosphere;
- Solar Granulation;
- Solar Rotation;
- Steady Flow;
- Atmospheric Circulation;
- Solar Atmosphere;
- Solar Magnetic Field;
- Spherical Harmonics;
- Solar Physics