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