Fig. 4: Spatial transport of alpha particles.

During the sawtooth crash in Fig. 3, we followed particles initialized with different kinetic energies K: a, b 35 keV, c, d 350 keV, e, f 3.5 MeV. The left column shows, in arbitrary units, snapshots of the radial density profile n_a(R) at the height of the midplane (z₀ = 0.27 m), integrated over ζ and all pitch angles. On the right, we show the density field n_a(R, z, ζ₀) in the poloidal plane around the toroidal angle ζ₀ = 0 at the time of snapshot (C) 0.3 ms. The particle velocities \(v=\sqrt{2K/{M}_{{{{{{\rm{a}}}}}}}}\) are shown for reference. These data were obtained in simulations of the reduced domain encircled by a red line in Fig. 1b. Very similar results are obtained for the full domain as shown in Supplementary Fig. 3c.