12 January

Solar wind speeds, measured at the ACE spacecraft, were indicative of
the arrival of the negative polarity coronal hole high speed stream (CH
HSS). Solar wind speeds began the period at approximately 370 km/s and
gradually increased to values between 500 – 540 km/s. Bt ranged from 2
nT to 9 nT and Bz varied between +/- 8 nT. The phi angle began the
period in a positive (away) sector until approximately 11/2100 UTC when
it changed to a negative (towards) and remained there throughout rest of
the period.

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