Doppler velocity observations obtained by the GONG instruments directly measure the nearly steady flows in the solar photosphere. The Sun's differential rotation profile is accurately determined from single observations. This profile is well represented by a fourth order polynomial which includes a rapidly rotating equator and a slight north-south asymmetry. Rotation profiles averaged over 27 day rotations of the Sun are sufficient to reveal the torsional oscillation signal - weak, 5 m/s, jet-like features associated with the sunspot latitude activity belts. A meridional circulation with poleward flow of about 20 m/s is also found from single observations and its spatial structure is well determined. Several of the observed characteristics of the surface flows suggest the presence of large convection cells. The convection spectrum is measured and found to have peak power for cells with wavelengths of about 50,000 km but the spectrum extends to much larger wavelengths. Day-to-day variations in the observed structure of the differential rotation and meridional circulation profiles indicate the presence of large-scale, nonaxisymmetric velocity signals which may be of solar origin. Studies correlating the convective flow patterns on consecutive days also indicate the presence of large cellular patterns that rotate at the Sun's rotation rate.
American Astronomical Society Meeting Abstracts #188
- Pub Date:
- May 1996