  Pattern forming instabilities induced by ultralow frequency sinusoidal
voltages were studied in a rod-like nematic liquid crystal by microscopic
observations and simultaneous electric current measurements. Two pattern
morphologies, electroconvection (EC) and flexodomains (FD), were distinguished;
both appearing as time separated flashes within each half period of driving. A
correlation was found between the time instants of the EC flashes and that of
the nonlinear current response. The voltage dependence of the pattern contrast
C(U) for EC has a different character than that for the FD. The flattening of
C(U) at reducing the frequency was described in terms of an imperfect
bifurcation model. Analysing the threshold characteristics of FD the
temperature dependence of the difference |e_1-e_3| of the flexoelectric
coefficients were also determined by considering elastic anisotropy.
