Chaos in driven Alfvén systems: boundary and interior crises

Chaotic transitions of nonlinear Alfvén waves via boundary and interior crises are studied. Alfvén crises are characterized using the unstable periodic orbits and their stable and unstable manifolds. In a period-3 periodic window of the bifurcation diagram, we identify a period-9 unstable periodic orbit that is responsible for both boundary and interior crises of two chaotic attractors. We demonstrate that these Alfvén crises arise from a homoclinic tangency.