Solar wind summary (Last 24 hours)

10th December

The southern pole coronal hole high speed stream (CH HSS) remained
geoeffective although it was beginning to show signs of decay. Solar
wind speed at the ACE spacecraft began the period in the low 500 km/s
range and ended near 450 km/s. Phi began the period in the negative
sector, but was variable after 09/1800 UTC. Bt reached 8 nT while Bz
dipped to -5 nT.

6th December

The solar wind environment at the ACE satellite indicated fairly nominal
conditions through about 06/0320 UTC. Wind speeds averaged about 450
km/s, IMF total field (Bt) ranged from 4-7 nT while the Bz component did
not vary much beyond +/- 5 nT. The phi angle was highly variable between
a negative (towards) and a positive (away) sector. After 05/0320 UTC,
phi rotated to a steady negative sector, wind speeds gradually increased
to near 475 km/s, Bt sharply increased to near 20 nT and Bz varied
between +16 nT to -6 nT. EPAM low energy particles also showed a gradual
increase indicating the possible arrival of a co-rotating interaction
region in advance of an anticipated negative polarity coronal hole high
speed stream (CH HSS).

4th December

The solar wind environment at ACE was modestly enhanced. Wind speed
hovered near 500 km/s. Phi was variable but predominantly negative. Bt
ranged from around 7 to 11 nT. Bz was mostly neutral or positive, with
-6 nT representing the maximum southern excursion.

2nd December

Wind speed and temperature at the ACE spacecraft began to climb in the
early part of the period, while density fell. Wind speed reached 640
km/s at 02/0255 UTC. Phi was mostly negative through the period. Bz
dipped as low as -10 nT at 01/2143 UTC then gradually returned to
neutral conditions as Bt declined. Wind speed dropped after 02/0300
UTC, ending near 500 km/s. The observations were consistent with the
presence of a high speed solar wind stream, although the observed
polarity was opposite of the hole that was expected, suggesting the
southern polar coronal hole is connected instead.

2nd December

Wind speed and temperature at the ACE spacecraft began to climb in the
early part of the period, while density fell. Wind speed reached 640
km/s at 02/0255 UTC. Phi was mostly negative through the period. Bz
dipped as low as -10 nT at 01/2143 UTC then gradually returned to
neutral conditions as Bt declined. Wind speed dropped after 02/0300
UTC, ending near 500 km/s. The observations were consistent with the
presence of a high speed solar wind stream, although the observed
polarity was opposite of the hole that was expected, suggesting the
southern polar coronal hole is connected instead.

1st December

Solar wind speed at the ACE spacecraft exhibited a gradual increasing
trend from about 385 km/s to near 460 km/s at period’s end. The IMF
total field (Bt) generally ranged from 8-11 nT. The Bz component was
variable between +9 to -8 nT through about 30/2100 UTC when the field
remained mostly north to about +5 nT. The Phi angle remained in a
predominately negative (towards) orientation. Low energy particles
detected by the EPAM instrument began rising slowly during the past 24
hours, perhaps signaling the approach of a co-rotating interaction
region in advance of an anticipated coronal hole high speed stream (CH
HSS).

28th November

Solar wind parameters indicated a nominal solar environment. Total
field ranged from 4 nT to 11 nT while the Bz component was variable
between +10 nT and -7 nT. Wind speed averaged about 360 km/s with a
peak of 430 km/s at 27/1938 UTC. The phi angle was in a predominately
negative (towards) sector with some positive (away) variability between
27/1200-1720 UTC.

26th November

The anticipated sector change and high speed stream has not materialized
yet. Solar wind was nominal at the ACE spacecraft, with speeds in the
mid 300 km/s range. Phi remained mostly positive and Bt was at or below
6 nT. Bz was mostly negative, dipping as low as -5 nT.

24th November

Solar wind parameters, measured at ACE, were indicative of waning
coronal hole high speed stream (CH HSS) influence. Solar wind speed
varied between 360 km/s and 480 km/s to begin the period, but eventually
settle down to consistently average near 380 km/s. Total field was
fairly steady between 6 nT to 7 nT, while the Bz component was mostly
negative, ranging between +4 nT and -7 nT. Phi angle remained mostly
positive (away) throughout the period.

23rd November

Solar wind parameters continued to be slightly enhanced through the
period, likely under weak coronal hole high speed stream (CH HSS)
influence. Solar wind speeds began the period near 360 km/s, but began a
gradual, yet unsteady climb just after the beginning of the new UT day.
Speeds reached a peak of 477 km/s at 23/0351 UTC, and averaged near 410
km/s for the second half of the period. Total field varied slightly
between 5 nT and 9 nT, while the Bz component was variable between +5 nT
and -7 nT. Phi angle was mostly oriented in a positive (away) sector.