1D excitation pulse propagation on a ring with the length
L = 512×Δx.
For Δx = 0.9 after relaxation transient the pulse is (almost) stationary.
For Δx = 0.6 the pulse shape and speed are unstable and alternate.
The pulse can not propagate on a small ring. For Δx < 0.5 it stops and disappears.
We will see next that this instability leads to spiral waves breakup.