12th December

Solar wind parameters indicated the arrival of a solar sector boundary
crossing (SSBC) followed by the onset of a positive polarity coronal
hole high speed stream (CH HSS). Solar wind speeds began the period
near 400 km/s with total field measurements around 5 nT. Density was
increasing through the first half of the period to near 20 p/cc. At
approximately 11/2227 UTC, phi angle switched into a positive (away)
sector, followed by a drop in density and an increase in total field,
temperature, and solar wind speed. Total field reached a maximum of 11
nT at 12/0122 UTC and remained enhanced through the end of the period.
The Bz component reached a maximum of -10 nT at 12/1040 UTC. Solar wind
speed continued to increase with end of period values near 500 km/s.

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