High-frequency and high-wavenumber solar oscillations

Abstract

We determine the frequencies of solar oscillations covering a wide range of degree (100 < l < 4000) and frequency (1.5 < ν < 10 mHz) using the ring diagram technique applied to power spectra obtained from Michelson Doppler Imager (MDI) data. The f-mode ridge extends up to l ≈ 3000, where the line width becomes very large, which implies a damping time that is comparable to the time period. The frequencies of high-degree f-modes are significantly different from those given by the simple dispersion relation ω²=gk. The f-mode peaks in power spectra are distinctly asymmetric, and use of an asymmetric profile increases the fitted frequency, bringing it closer to the frequencies computed for a solar model.