Regensburg 2010 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Interfaces I
MM 15.5: Vortrag
Montag, 22. März 2010, 15:45–16:00, H5
Ordering dynamics of snow under isothermal conditions — •Henning Löwe, Johanna Spiegel, and Martin Schneebeli — WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
We have investigated the morphological evolution of laboratory snow at different temperatures by means of X-ray tomography. The collective dynamics of the bicontinuous ice-vapor system is monitored by the evolution of the two-point correlation function C(r,t) and an ice thickness distribution. We observe the absence of dynamic scaling and reveal fundamentally different classes of length scales: The first class comprises the mean ice thickness and the ice volume per surface area. Both follow a power law l∼ t1/z in time, where z≈ 3 is in accordance with coarsening of a locally conserved order parameter. A second class of length scales is defined by the inverse partial derivatives of C(r,t) at the origin. The second class shows a slower growth with anomalous power law scaling z≈ 5. The two different power laws are consistent with fractal coarsening and reveals the persistence of long-range correlations from initial, dendritic conditions. A third class of length scales is defined by the first zero crossing of C(r,t) on the coordinates axes which display a non-monotonic evolution with a strong anisotropy between vertical and horizontal directions. We attribute this behavior to larger scale structural relaxations of the ice network which apparently leave the small scale, interfacial relaxations unaffected. However, vice versa it poses the question how structural mobility is induced by coarsening.