Solar wind summary (Last 24 hours)

1st December

Solar wind parameters, as measured at the ACE spacecraft, indicated the
onset of a positive polarity coronal hole high speed stream (CH HSS).
Solar wind speeds began to increase from initial values near 360 km/s at
the beginning of the period, and reached maximum values near 585 km/s
early in the new UTC day. Speeds eventually stabilized just below 500
km/s towards the end of the period. The IMF total field began the period
with minor fluctuations between 5 nT and 10 nT, then increased to just
below 14 nT near the end of the UTC day, before steadily decreasing to
finish the period near 9 nT. The Bz component of the IMF was variable
between +11 nT and -11 nT until the last few hours of the period, where
it remained positive to finish out the day. Phi angle was mostly
positive (away) throughout the period. ACE/EPAM data indicated an
enhancement of low energy particles, indicating the approach of a
possible transient that has the potential to give Earth a glancing blow.

30th November

Solar wind parameters remained at background levels. However, a gradual
but steady increase in solar wind speed was observed throughout the
period following brief and intermittent phi angle changes. Once the phi
angle settled back into a positive (away) orientation, speeds leveled
off near 360 km/s for the rest of the period. The IMF total field
remained fairly consistent between 6 nT to 8 nT until the last few hours
where it realized a slight enhancement to 10 nT. The Bz component varied
between +7 nT and – 11 nT to start the period and remained variable

29th November

Solar wind parameters continued at background levels. Solar wind speeds
remained predominantly steady near 280 km/s with isolated increases to
near 340 km/s. Total field fluctuated between 5 nT and 9 nT with the Bz
component drifting as far southward as -9 nT. Phi angle remained mostly
in a positive (away) sector throughout the period.

28th November

Solar wind conditions remained at nominal levels. Solar wind velocity
was mainly at background levels, reaching a peak speed briefly of 344
km/s. The interplanetary magnetic total field held steady near 5 nT for
the entire period. The Z-component of the IMF (Bz) was weakly northward
for most of the day.

27th November

Following a solar sector boundary (SSB) change that occurred at about
26/1615 UTC, solar wind velocity increased slightly, from approximately
280 km/s to approximately 320 km/s. Velocities remained steady near the
320 km/s mark through most of the period before starting to decrease
just after 0400 UTC. IMF total field displayed a very slow enhancement
throughout the period, increasing from 2 nT at the beginning to 5 nT by
the end of the period. IMF Bz remained mostly positive with isolated
ventures southward near the beginning of the period. Bz ended the period
at 2 nT.

26th November

Solar wind was nominal during the day. Solar wind velocity was steady
near 325 km/s for the first half of the period, but decreased sharply at
approximately 0200 UTC. With fluctuations between 254 km/s and 330
km/s, the second half of the period ended near 270 km/s. The total field
ranged from 1-3 nT and the southward component of the interplanetary
magnetic field fluctuated between +/-2 nT. The Phi angle remained
predominantly in a negative (towards) sector with brief interludes into
the positive (towards) sector.

25th November

Solar wind continued to be under nominal conditions. Solar wind speeds
ranged from 292 km/s to 361 km/s with the total field fairly steady
between 2 nT and 4 nT. The Bz component was variable between +4 nT and
-3 nT. Phi angle was predominantly negative (towards) throughout the

24th November

Solar wind parameters indicated a recovery from the recent transient
event and a return to nominal solar wind conditions. Total field was
initially elevated at 10 nT before returning to the 1 nT to 6 nT range
after 23/1800 UTC. Solar wind speed ranged between 244 km/s and 390
km/s. The Bz component initially ranged between +8 nT and -7 nT before
decreasing to between +/-5 nT for the rest of the period. Phi angle was
variable between positive (away) and negative (towards) sectors
throughout the period.

23rd November

Solar wind speed was generally in the low to mid 300 km/s range at the
ACE spacecraft. A weak transient passage may have occurred after 22/0736
UTC when the phi angle abruptly changed from negative to a more positive
orientation, Bt jumped slightly and Bz became entirely positive. During
this episode, temperature dropped slightly and density rose. By about
22/1625, Bz had become negative (approx -2nT) and began to rise

22nd November

Solar wind speed at the ACE spacecraft remained at nominal levels,
staying well under the 350 km/s mark. Phi angle was mostly negative with
a slight oscillation into positive territory for a short period.
Bt displayed a slow but steady increase from just below 2 nT to just
over 4 nT. Bz never dropped below -3 nT and finished the period at a
steady 4 nT.