Spiral breakup and defect dynamics in a model for intracellular Ca2+ dynamics

Pattern formation is investigated near the breakup instability of rotating spiral waves in a model for intracellular Ca'S dynamics. Our results show t hat spiral breakup is strongly dependent on the inactivation parameter of t he inositol 1,4,5 triphosphate receptor ion channel. We compute the pulse t rain instability reponsible for spiral breakup and investigate the influenc e of the system size. The instability of planar pulse trains is a long wave length (with respect to the perturbations) Eckhaus instability. that appear s upon decrease of the wavelength of the pulse train, Secondly, we study th e dynamics of topological defects in the spatiotemporally chaotic state eme rging from the spiral breakup. This regime is characterized by a variance o f the number of defects that is considerably smaller than the corresponding mean value. Global characteristics like the creation and annihilation rate and the probability distribution of the number of defects are calculated. The defect transport is characterized by its diffusivity. Most defects move subdiffusively within their lifetime as a consequence of meandering. (C) 1 999 Published by Elsevier Science B.V. All rights reserved.