“Linear input tippy bucket” substorm model. Accumulated magnetic reconnection ε-energy starting from 3 h prior to the SSS onsets up to the onsets of the SSSs. Top x-axis marks the time in hours from the SSS onset, while bottom x-axis marks the linear effectivity of the accumulated energy in causing an SSS. The effectivity is assumed to increase linearly from 0% at 3 h prior to the SSS onset up to 100% at the SSS onset.