  The SWICS instrument aboard the ACE satellite has detected frequent intervals
in the slow solar wind and interplanetary coronal mass ejections (ICMEs) in
which C6+ and other fully stripped ions are strongly depleted, though the
ionization states of elements such as Si and Fe indicate that those ions should
be present. It has been suggested that these outlier or dropout events can be
explained by the resonant cyclotron heating process, because these ions all
have the same cyclotron frequency as He2+. We investigate the region in the
corona where these outlier events form. It must be above the ionization
freeze-in height and the transition to collisionless plasma conditions, but low
enough that the wind still feels the effects of solar gravity. We suggest that
the dropout events correspond to relatively dense blobs of gas in which the
heating is reduced because local variations in the Alfven speed change the
reflection of Alfven waves and the turbulent cascade. As a result, the wave
power at the cyclotron frequency of the fully stripped ions is absorbed by He2+
and may not be able to heat the other fully-stripped ions enough to overcome
solar gravity. If this picture is borne out, it may help to discriminate
between resonant cyclotron heating and stochastic heating models of the solar
wind.
