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04210030forecast_discussion.txt
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:Product: 04210030forecast_discussion.txt
:Issued: 2014 Apr 21 0030 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
#
Solar Activity
.24 hr Summary...
Occasional low-level C-class flares kept activity at low levels. The
largest event of the period was a C6 event at 20/0813 UTC from Region
2033 (N11W78, Hsx/alpha). A Type II radio emission (est 529 km/s)
accompanied the C6 flare. LASCO C2 imagery detected a slow-moving CME
(236 km/s line-of-sight velocity) lifting off the NW limb at 20/0848
UTC. Most material moved north of the ecliptic and did not appear to be
geoeffective. Most regions were stable or decaying. The three largest
regions, 2034 (N04W66, Eko/beta-gamma), 2035 (S16W43, Eai/beta-gamma),
and 2036 (S17E68, Dac/beta-gamma) decreased in areal extent from
yesterday but retained their beta-gamma magnetic complexity.
.Forecast...
C-class activity is expected to continue through the forecast period
keeping solar activity at low levels. Further moderate (R1-minor)
activity is likely on day one (21 Apr) before diminishing to a chance on
days two and three (22-23 Apr) as the large, complex regions exit around
the west limb.
Energetic Particle
.24 hr Summary...
The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels for the period. The 10 Mev greater than 10 pfu
proton event (S1-minor) which began on 18/1525 UTC reached a maximum of
58 pfu at 19/0105 UTC before beginning to decline. The decline was
interrupted when an interplanetary (IP) shock passage was detected at
ACE at 20/1057 UTC. 10 MeV flux briefly rose from 15 pfu to near 30 pfu
before plummeting below the 10 pfu threshold at 20/1155 UTC, signaling
the end of the proton event.
.Forecast...
The greater than 2 MeV electron flux at geosynchronous orbit is expected
to be at normal to moderate levels for the forecast period. The greater
than 10 MeV proton flux at geosynchronous orbit is expected to be
elevated, but below the 10 pfu threshold. It should gradually return to
nominal levels over the next three days with a slight chance for another
event on days 1-2 (21-22 Apr).
Solar Wind
.24 hr Summary...
At 20/1057 UTC an IP shock was observed at ACE. Wind speeds jumped from
about 525 km/s to a maximum of 764 km/s by 20/1125 UTC before
diminishing to around 675 km/s where they were steady for the remainder
of the period. Bt increased from 6 to a maximum of 21 nT by 20/1114 UTC
after which it declined to a minimum of 4 nT by 1538 UTC before rising
slowly to settle near 11 nT. Bz varied from 21 to -9 nT, but never
staying in negative territory for very long. These observations
suggested the arrival of the anticipated 18 Apr CME.
.Forecast...
In the wake of the CME arrival, the current disturbed conditions are
expected to slowly diminish over the next three days (21-23 Apr). A
weak negative coronal hole high speed stream may keep conditions from
returning to a purely nominal state.
Geospace
.24 hr Summary...
At 20/1057 UTC, a 24 nT geomagnetic sudden impulse was recorded at the
Boulder magnetometer. Geomagnetic activity subsequently reached active
levels at 20/1235 UTC and minor storm (G1) levels by 20/1301 UTC. The
relatively benign behavior of Bz kept the activity from exceeding minor
storm levels. The remainder of the period was characterized by active
levels.
.Forecast...
Minor (G1) storm conditions may persist into the first synoptic period
of day one (21 Apr) with an overnight sub-storm before diminishing to
unsettled to active levels for day 2 (22 Apr). Day three (23 Apr) should
see a return to quiet to unsettled levels.