Abstract

Dissipative structures emerged in spatially extended systems driven far from equilibrium are known to undergo secondary bifurcations [1,2]. Recently we have reported the experimental observation of a transition between positive and negative hexagonal patterns in a sodium vapor cell with feedback mirror placed into an external magnetic field [3]. It was found to be in good accordance with a microscopic model. A specific feature of hexagons in our system is that the spatial harmonics strongly interact with the primary mode leading to a secondary instability. (For 2D geometry the lowest spatial harmonics correspond to a length scale which is by $\sqrt{3}$ smaller than the one of primary hexagons.)

© 1996 IEEE