Fig. 14

Mechanisms underlying the sigh-like spiking solution. A sigh-like spiking solution of (7a)–(7e) (black curve), projected to (A) \((v, h, ca_{i})\)-space and (B) \((c, c_{\mathrm{tot}}, l)\)-space. Also shown are projections of \(\mathscr {M}_{s}\) (colored surface) and \(\mathscr {M}_{ss}\) (red curves, solid where attracting, dashed otherwise). The yellow star and circle indicate points where the trajectory approximately reaches \(\mathscr {M}_{s}\) and \(\mathscr {M}_{ss}\), respectively. The yellow diamond in \(\mathscr {M}_{ss}\) represents the subcritical AH bifurcation of the fast-slow subsystem \((v, h, ca_{i},l)\)