Sensitivity to the applied boundary conditions of the solar eigenfrequency spectrum with periods near five minutes

Abstract

The existence of an anomalous component in the outer solar boundary conditions may cause large deviations from the standard eigenfrequency spectrum. Relaxation of the standard boundary conditions introduces alterations in the eigenfrequencies; for a given mode defined by spherical harmonic of order l and radial number n, a range of frequencies is possible, with the eigenfrequency nonlinearly dependent on the complex ratio between the standard and anomalous solution components. The observed ridges of power in the diagnostic diagram (ℓ abscissa and ω ordinate) lie below the theoretical ridges, i.e., curves defined by constant n and standard boundary conditions. Using a linear nonadiabatic nonradial model for solar oscillations, anomalous boundary conditions were found to extend the standard theoretical ridges upward by roughly 1/3 ridge separation and downward by 1/3 ridge separation, encompassing the location of the observed ridges. The growth rate of a given mode is extremely dependent on the ratio of the anomalous and standard solutions present in the mode. If linear theory is adequate, simultaneous ℓ-ω plots of intensity and velocity may be used to infer the ratio between standard and anomalous solution components.