ASYMMETRY IN VELOCITY AND INTENSITY HELIOSEISMIC SPECTRA - A SOLUTIONTO A LONG-STANDING PUZZLE

We give an explanation for the opposite sense of asymmetry of the sola r acoustic mode lines in velocity and intensity oscillation power spec tra, thereby solving the half-decade-old puzzle of Duvall and coworker s. The solution came after comparing the velocity and intensity oscill ation data of medium angular degree 1 obtained from the Michelson Dopp ler Imager instrument on board the Solar and Heliospheric Observatory with the theoretical power spectra. We conclude that the solar noise i n the velocity and intensity spectra is made up of two components: one is correlated to the source that is responsible for driving the solar p-modes, and the other is an additive uncorrelated background. The co rrelated component of the noise affects the line profiles. The asymmet ry of the intensity spectrum is reversed because the correlated compon ent is of a sufficiently large level: while the asymmetry of the veloc ity spectrum remains unreversed because the correlated component is sm aller. This also explains the high-frequency shift between velocity an d intensity at and above the acoustic cutoff frequency. A composite so urce consisting of a monopole term (mass term) and a dipole term (forc e due to Reynolds stress) is found to explain the observed spectra whe n it is located in the zone of superadiabatic convection at a depth of 75 +/- 50 km below the photosphere.