Solar wind summary (Last 24 hours)

31 December


ACE data indicated nominal solar wind conditions through most of the
period, with a gradual increase in activity towards the end. Wind speed
began the period just under 310 km/s with a gradual increase noted just
after 30/1400 UTC, peaking at 407 km/s. Conditions settled back down
into the lower 300 km/s range by 30/1500 UTC, but began a gradual
increase throughout the remainder of the period, ending just under 400
km/s. IMF Bt was fairly consistent near 4 nT to 6 nT through 31/0700 UTC
when it dropped slightly to 3 nT to 5 nT. IMF Bz ranged between 4 to -5
nT throughout the period. IMF Phi data indicated a positive-polarity
(Away) solar sector until 31/0739 UTC, when it switched to a
predominantly negative (Towards) orientation.

30 December


The solar wind environment at the ACE spacecraft was nominal. The phi
angle remained positive through the period and speed remained in the low
to mid 300 km/s range. Bt was less than or equal to about 7 nT during
the period and Bz never fell below about -6 nT.

29 December


The solar wind environment at the ACE spacecraft was nominal. Wind
speed rose from near 280 km/s to end the period near 360 km/s. The phi
angle was generally positive with some occasional fluctuations into a
negative orientation. Bz ranged from about 6 to -5 nT while Bt
approached 9 nT early in the period.

28 December


Solar wind was nominal. Speed at the ACE spacecraft remained in the
upper 200 to lower 300 km/s range. The phi angle was predominantly
positive for the first half of the period, switching to a more negative
orientation between 28/0000-0900 UTC before returning to a positive
orientation. Bz was generally neutral, ranging between +8 and -5 nT. Bt
began around 9 nT but decreased to about 5 nT after 27/1900 UTC.

27 December


ACE data indicated nominal solar wind conditions. Solar wind speed began
the period near 270 km/s, dipped to as low as 243 km/s before beginning
a steady climb to peak at 325 km/s at 27/0820 UTC. Speeds became
sporadic near the end of the period, but ended the summary period where
it began, at 270 km/s. IMF total field exhibited a steady climb from 2
nT at the beginning of the period to 7 nT at the end. The Bz component
began the period with a maximum southward deflection near -2 nT, but
also exhibited a steady increase and ended the period also at
approximately 7 nT. IMF Phi data indicated a positive-polarity (away)
sector until approximately 26/1800 UTC, then shifted to a
negative-polarity (toward) sector for the rest of the period.

26 December


ACE data indicated slightly enhanced solar wind conditions at the
beginning of the period, with the IMF total field reaching 11 nT and a
maximum Bz deflection of -10 nT. This enhancement was likely associated
with a solar sector boundary crossing that occurred earlier in the
period, with the effects being short-lived. Nominal conditions returned
after 26/1600 UTC and have lasted throughout the rest of the period. The
coronal hole high-speed stream (CH HSS) that was expected to commence
today has yet to materialize. Wind speed ranged from 255 to 296 km/s at
the beginning of the period before decreasing and stabilizing to near
270 km/s at the end of the period.

25 December


ACE data indicated nominal solar wind conditions. Solar wind speed began
the period just under 290 km/s, trailing off to near 250 km/s before
beginning a gradual climb to nearly 340 km/s at its peak around 25/0400
UTC. Just after it reached its max, it began a steady decrease through
the end of the period, where it ended as it began at just below 290
km/s. IMF Bt was steady between 3 to 6 nT range for the first half of
the period, then began climbing to 10 nT to 12 nT, where it remained
through the end of the period. IMF Bz was predominantly southward during
the first half of the period, before fluctuating between +/-5 nT through
0400 UTC, the dropping even more southward to end the period at a steady
-9 nT. Phi data indicated the Earth was within a positive-polarity
(away) solar sector through approximately 0400 UTC when it made a slow
but steady transition to a negative (towards) orientation.

24 December


ACE data indicated nominal solar wind conditions during the period. Wind
speed ranged from as low as 264 to a peak speed of 341 km/s. IMF Bt
continued in the 1 to 4 nT range, while IMF Bz fluctuated between +3/-3
nT. IMF Phi data indicated a positive-polarity (Away) solar sector
orientation throughout the period.

23 December


Solar wind parameters, measured at ACE, were indicative of a nominal
solar wind environment. Solar wind speed slowly decreased from initial
values near 350 km/s to end-of-period values near 300 km/s. Total field
strength values were steady in the 4 nT to 6 nT range while the Bz
component ranged between +4 nT to -4 nT.

22 December


Solar wind parameters, measured at ACE, were indicative of a nominal
solar wind environment. Solar wind speed was steady near 350 km/s.
Total field strength values ranged from 4 nT to 6 nT while the Bz
component ranged from +4 nT to -4 nT.