21st October

Solar wind measurements at the ACE spacecraft reflected the influence of
a positive polarity coronal hole high speed stream (CH HSS). Wind speed
began around 500 km/s and increased to near 600 km/s by 21/0500 UTC and
to almost 700 km/s by the end of the period. Phi remained positive. Bt
was at or below 10 nT while Bz fluctuated between 7 and -9 nT in the
first half of the period, becoming mostly positive or neutral after
21/0000 UTC.

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