On-off convection: Noise-induced intermittency near the convection threshold

A phenomenological nonlinear stochastic model of intermittency experimentally observed by Behn, Lange, and John [Phys. Rev. E 58, 2047 (1998)] in the electrohydrodynamic convection in nematics under dichotomous noise is proposed. This has the structure of the two-dimensional Swift-Hohenberg equation for local convection variable with fluctuating threshold. Numerical integration of the model equation shows intermittent emergence of convective pattern. Its statistics are found to obey those known, so far, for on-off intermittency. In the course of time, although the pattern intensity changes intermittently, no evident pattern change is observed. Adding additive noise, we observe an intermittent change of convective pattern.