This plot shows the decrease in the Dst index (solid line) and the increase in the energy content of the ring current between L = 3 and 5 (crosses) observed during a major geomagnetic storm that occurred in February 1986. Following a slow two-day build-up, the storm reached maximum intensity early on February 9, by which time the energy content of the ring current had grown to nearly sixteen times its quiet-time value and the Dst had dropped to -312 nT. The sharp rise in ring current energy content during the latter part of February 8 is due to the strong injection into the ring current of ionospheric ions; the rapid initial recovery on February 9 is due to the rapid loss of these same ions. Full recovery of the ring current to its quiet-time state required over a month.

(Source: Hamilton, D. C., et al., Ring current development during the great geomagnetic storm of February 1986, J. Geophys. Res., 93, 14343, 1988.)