The onset of the AGB wind tied to a transition between sequences in the period-luminosity diagram

We link the onset of pulsation-enhanced, dust-driven winds from asymptotic giant branch (AGB) stars in the Magellanic Clouds to the star's transition between period--luminosity sequences (from B to C'). This transition occurs at ~60 days for solar-mass stars, which represent the bulk of the AGB population: this is the same period at which copious dust production starts in solar-neighbourhood AGB stars. It is contemporaneous with the onset of long-secondary period (LSP) variability on sequence D. The combined amplitude of the first-overtone (B+C') and fundamental (C) modes and (perhaps) long-secondary period (D; LSP) variability appears to drive a sudden increase in mass-loss rate to a stable plateau, previously identified to be a few x 10^-7 solar masses per year. We cite this as evidence that pulsations are necessary to initiate mass loss from AGB stars and that these pulsations are significant in controlling stars' mass-loss rates. We also show evidence that LSPs may evolve from long to short periods as the star evolves, counter to the other period-luminosity sequences.