Two Regimes of Glitching: The Crab and Vela Placed on One Quantitative Footing

The Crab and Vela pulsars are both young, both glitch, and otherwise could hardly differ more. This study places their glitch behaviour on a single quantitative footing from their published timing parameters and catalogue summaries. The Crab's spin-down luminosity exceeds Vela's by a factor of 64, yet its glitch activity requires a reservoir of only 0.004 per cent of its moment of inertia, against 2.01 per cent for Vela, a factor of 524 smaller. Their mean glitch sizes differ by a factor of about 67. The contrast is not a matter of degree but of regime: Vela's glitches are structural events that reorganise its interior angular momentum, while the Crab's typical glitches are a small perturbation that its rapid spin-down replenishes almost immediately. Models calibrated on one pulsar should not be carried to the other without rescaling by the numbers computed here. This study is simulated and computed from stated assumptions; it is not a measurement.