Very Long Lived Wave Patterns Detected in the Solar Surface Velocity Signal

Open Access
Publisher Website
Google Scholar
Abstract
The wavelike pattern of velocity variations in the outer layers of the Sun known as the "torsional oscillations" is shown to consist of long-lived inertial oscillation waves. The dominant pattern which was first identified at Mount Wilson and which has now been observed with the Michelson Doppler Imager instrument and the Global Oscillation Network Group, may be the m = 0 component of a hierarchy of inertial oscillation waves having m-values up to 8. The identification is based on the geometric structure and the relationship of the pattern in adjacent bands of latitude. It is found that the cross-correlation between adjacent latitude bands consists almost exclusively of an oscillatory component with little or no evidence of a peak at 0 lag. Since the pattern has a global extent in the longitudinal direction with the wave pattern being coherent over essentially the whole solar circumference, a convective interpretation cannot be supported when the latitudinal structure is limited to less than 3° of latitude. These wavelike patterns define a rotation rate which is similar to that found for the magnetic features but which deviates in zones with magnetic activity in the sense that the m = 1 component rotates more slowly while the m = 3 and 4 components rotate more rapidly.