Effects of certain analysis procedures on solar global velocity signals
We examine the data reduction procedures used by Howard and colleagues to deduce global solar velocities from the orginal Mount Wilson Doppler-magnetograph record. We demonstrate that removing daily rotation ''ears,'' and zero offset signals will greatly attenuate east-west global velocities of longitudinal wavenumber m< or =5. In addition we show that, because global velocity patterns are expected on theoretical grounds to have variable phase speeds in longitude, the construction of synoptic maps can severely attenuate high wavenumbers. The combination of these two effects can easily reduce an original periodic east-west flow velocity of peak amplitude 100 m s/sup -1/ to 10 m s/sup -1/ or less for any wavenumber. We demonstrate further that a velocity spectrum, obtained from a nonlinear spherical convection model for a case in which a differential rotation similar in amplitude and profile to the Sun, is attenuated to rms residual velocities close to or within the upper limits obtained by Howard and LaBonte. However, somewhat more power than they find is retained in variations of the daily rotation rate.
- Research Organization:
- High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado
- OSTI ID:
- 6636041
- Journal Information:
- Astrophys. J.; (United States), Vol. 241:2
- Country of Publication:
- United States
- Language:
- English
Similar Records
Final scientific report for DOE award title: Improving the Representation of Ice Sedimentation Rates in Global Climate Models
Large-scale periodic solar velocities: an observational study. Technical report