Traveling waves in the sunspot chromosphere: Problems and puzzles of experiments

The difficulties of the primary interpretation of wave processes observed in the sunspot chromosphere are discussed. Frequency filtering is shown to be helpful in revealing traveling waves more clearly, which eventually affects the objectivity of estimating their parameters. The measured horizontal phase velocities are 40–70 km s−1 for umbrae and 30–70 km s−1 for penumbrae. Analysis of high-cadence observations has revealed an altitude inversion of the spatial localization of the three-minute oscillation power. It is pointed out that the pattern of umbral traveling waves is not constant and periodically gives way to the pattern of standing waves.