Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 25: Granular Matter / Contact Dynamics

DY 25.1: Invited Talk

Wednesday, April 3, 2019, 09:30–10:00, H3

Why the desert is not flat — •Klaus Kroy — Institut für Theoretische Physik, Universität Leipzig, Brüderstraße 16, 04003 Leipzig

Windblown sand creates a distinct hierarchy of mobile landforms on Earth and other heavenly bodies [1], ranging from neat tapestries of ripples to vast fields of shifting dunes. I explain how they form, and what determines their characteristic shapes, sizes, and migration dynamics. This involves three crucial physical mechanisms: spontaneous turbulent symmetry breaking, breaking of scale invariance by an emergent mesoscale, and particle sorting. Collectively, they give rise to the notion of a forbidden wavelength gap that can only be inhabited by a peculiar structure, commonly known as megaripple but mechanistically better understood as as a mini-dune [2], which may be the predominant aeolian structure on Mars [3].

[1] A. G. Hayes: Dunes across the solar system, Science 360 (2018) 960.

[2] M. Lämmel, A. Meiwald, H. Yizhaq, H. Tsoar, I. Katra, and K. Kroy: Aeolian sand sorting and megaripple formation, Nature Physics 14 (2018) 759.

[3] D. C. Berman, M. R. Balme, J. R. Michalski, S. C. Clark, E. C. S. Joseph: High-resolution Investigations of Transverse Aeolian Ridges on Mars, Icarus 312 (2018) 247.