Comparison of the Calibrated Mdi and Golf Signals

Low-frequency p-modes have relatively small amplitudes and are set against the background of granula-tion and active regions on the solar surface. We apply a number of time series analysis techniques to separate these modes from trends and the background. The calibrated signals of both the MDI and GOLF instruments are processed in the following steps: 1) whitening and gap lling; 2) signal extraction and de-modulation in given frequency bands; and 3) separation of noise and signal by Singular Spectrum Analysis (SSA). The resulting signals are compared in the frequency and time domains. Particular attention is paid to spectral features at very low frequencies and the tentative identiication of low radial order p-modes.