Single thread destabilises, Phase 3. Panel a: final positions and energies of protons (for the case where background resistivity is omitted from every orbit calculation)together with purple isosurface(s) of critical current and interpolated magnetic field lines (grey). The key to orbit energies is given in the colour bar displayed above panel b, where the initial and final energy distributions of both electrons (red) and protons (blue) are displayed, for cases where background resistivity is omitted (dashed) or included (solid lines), while the black solid histogram shows an example of the initial energy distribution.