Weak-to-strong transition of an Alfvénic cascade
= Weak-to-strong transition of an Alfvénic cascade
{title2=$l_{\perp,*}\sim L_\perp\chi_0^2$}
In a <weak Alfvénic cascade> at fixed $l_\parallel$, $\chi=\tau_A/\tau_{\rm nl}\propto l_\perp^{-1/2}$ grows as the perpendicular scale shrinks. If its outer value is $\chi_0\ll1$ at $L_\perp$, it reaches order one at the displayed scale. Beyond it the weak-interaction ordering fails and a <critical balance> model may become appropriate.