Solar wind summary (Last 24 hours)

10 April


ACE data indicated a return to nominal conditions as the period
progressed. Wind speed ranged from 501 km/s to 385 km/s with a gradual
decrease during the period. IMF total field intensity ranged from 3 nT
to 6 nT. The Bz component of the IMF ranged from 3 nT to -4 nT, but was
largely neutral after 10/0000 UTC. IMF Phi data indicated a
positive-polarity solar sector throughout the period.

9 April


Solar wind conditions were slightly elevated during the period with
speeds between 380 km/s and 517 km/s. Total field ranged from 2nT to 7
nT with the Bz component between 5 nT and -3 nT. The Phi angle gradually
transitioned from a negative-polarity (toward) to a positive-polarity
(away) solar sector during approximately 08/2000 – 09/0000 UTC.

8 April


ACE data indicated minor solar wind activity. Wind speed ranged from 358
to 500 km/s with a gradual increase during the first half of the period
and a gradual decrease during the latter half. IMF Bz was variable in
the 9 to -8 nT until approximately 07/1900 UTC, then hovered around zero
for the rest of the period. IMF Bt varied from 1 to 10 nT until
approximately 07/1830 UTC, then became less variable in the 4 to 8 nT
range. Phi data indicated a positive-polarity (Away) solar sector during
the period.

7 April


Solar wind speed at the ACE spacecraft remained in the mid to upper 300
km/s range throughout the period. Phi remained negative. Bz was
generally neutral while Bt decreased slightly from a high of 13 nT at
the beginning of the period to end near 9 nT. The EPAM instrument
indicated a slight rise in low energy particle flux suggesting the
presence of an approaching transient feature.

6 April


Solar wind speed at the ACE spacecraft declined from around 500 km/s to
end the period in the upper 300 km/s range. Phi remained negative
throughout the period. Bt reached a peak near 18 nT at 06/0200 UTC
while Bz remained mostly neutral or positive through most of the period,
although it did dip to near -5 nT at 05/1445 UTC. Density showed a
steady increase between 05/15-22 UTC before dropping abruptly.

5 April


Some perturbations in the solar wind characteristics and a slow rise in
low energy particle flux were evident at the ACE spacecraft. After
05/0700 UTC, Phi shifted from positive to negative and Bt began
increasing to a peak of about 10 nT and Bz dipped to a minimum of -8 nT.
Wind speed hovered in the low to mid 400 km/s range until about 05/0930
UTC after which it began to approach 500 km/s and ended the period at
501 km/s. The sum of these observations suggest the passage of the CMEs
from 01-02 April.

4 April


ACE data indicated nominal solar wind conditions during the period. Wind
speed ranged from 357 to 487 km/s with a gradual increase during the
latter half of the period. The Bz component of the IMF was variable in
the -4 to 6 nT range. IMF total field intensity ranged from 2 to 7 nT.
ACE EPAM data showed a gradual increase on all channels, likely
indicating the approach of CMEs observed on 01-02 Apr.

3 April


ACE data indicated nominal solar wind conditions. Wind speed slowly
decreased from 461 – 360 km/s during the period. IMF Bt and Bz
signatures were unremarkable. IMF Phi data indicated a positive-polarity
(away) solar sector during the period.

2 April


Solar wind was slightly enhanced. However, no evident CME signatures
were observed from the expected arrival of the first of a series of CMEs
that occurred between 28 and 30 Mar. Solar wind speed ranged from 362 to
502 km/s. Total field was relatively steady between 4 nT and 7 nT, while
the Bz component was variable at +/- 5 nT. Phi data indicated a
positive-polarity (away) solar sector during the period.

1 April


ACE data hinted at possible weak, positive-polarity high-speed stream
effects, given the enhanced solar wind speed and temperature. Wind speed
was in the 350 to 446 km/s range. IMF Bt (total field) ranged from 2 to
7 nT. The Bz component of the IMF was in the 6 to -5 nT range with a
mostly-southward period during approximately 31/1330 – 1630 UTC. IMF Phi
values reflected a positive-polarity sector for most of the period.