Speaker
Vladimir Nosenko
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.J504.pdf
Mode Coupling in Two-Dimensional Complex Plasma Crystals
V. Nosenko, J. K. Meyer, I. Laut, S. K. Zhdanov, H. M. Thomas
Deutsches Zentrum für Luft- und Raumfahrt (DLR), D-82234 Weßling, Germany
Wave modes of many physical systems can become coupled to each other. Mode coupling
can lead to new interesting effects such as the mode-coupling instability (MCI) which was
predicted theoretically [1] and observed experimentally in two-dimensional (2D) complex
plasma crystals [2]. MCI occurs when the dispersion relations of the two dust-lattice wave
modes, longitudinal in-plane (L) mode and transverse vertical (TV) mode intersect. In the
vicinity of their intersection, a new hybrid mode appears which is unstable. If not
suppressed by the neutral gas friction, it will grow exponentially with time and can result in
the crystal melting. A prominent characteristic feature of MCI is mixed polarization, where
traces of the L mode can be measured in the transverse vertical spectra and vice versa [2]. It
was previously believed that the mixed polarization could only occur when the modes
cross.
In this contribution, we report on the experimental observation of mode coupling and mixed
polarization of the longitudinal in-plane and transverse vertical wave modes in a 2D
complex plasma crystal in the absence of mode crossing [3]. The coupling manifests itself
in traces of the TV mode appearing in the measured longitudinal spectra. The observations
are corroborated in molecular dynamics simulations. A theoretical analysis of the modes in
a plasma crystal with finite temperature predicts the ratio of the trace to the principal mode
which is in a good agreement with the experiment and simulations.
1. A. V. Ivlev and G. Morfill, Phys. Rev. E 63, 016409 (2001).
2. L. Couëdel, S. K. Zhdanov, A. V. Ivlev, V. Nosenko, H. M. Thomas, and G. E. Morfill, Phys. Plasmas 18,
083707 (2011).
3. J. K. Meyer, I. Laut, S. K. Zhdanov, V. Nosenko, and H. M. Thomas, Phys. Rev. Lett. 119, 255001 (2017).
