DoppelmodusPulsationen

DoppelmodusPulsationen is a term used in physics and astrophysics to describe the simultaneous excitation of two distinct pulsation modes within a single system. In this context, the observed signal comprises two dominant frequencies, f1 and f2, whose superposition produces beat patterns and a more complex light or displacement curve than a single-mode oscillator.

The term is especially associated with variable stars in astronomy, where some stars pulsate in two radial modes at once, known as double-mode or RRd stars. In such stars, the fundamental mode and the first overtone are excited, typically with a period ratio around P1/P0 ≈ 0.74, providing powerful constraints on stellar structure through asteroseismology. DoppelmodusPulsationen can also arise in other systems, such as laser cavities operating in two longitudinal modes or mechanical structures with two nearly degenerate natural frequencies, where nonlinear coupling or external forcing sustains both modes.

The identification relies on time-series analysis, including Fourier decomposition, to separate the two frequencies and study their amplitudes, phases, and stability. The phenomenon sheds light on mode selection, resonance, and energy transfer between modes, and it poses challenges for models of nonlinear oscillations.

While widely studied under different names in various fields, the overarching concept remains the same: a system exhibits two coexisting oscillation patterns that interact. See also: multi-mode pulsation, non-linear dynamics, asteroseismology.