NOAA SEC Report of Solar-Geophysical Activity 4 Apr 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 04 2200 UT
# Prepared jointly by the U.S. Dept. of Commerce, NOAA,
#Space Environment Center and the U.S. Air Force.
#
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 094 Issued at 2200Z on 04 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  03/2100Z
to 04/2100Z:  Solar activity was moderate due to four M-class events
during the past 24 hours. The largest of these was an M2 at 1222Z.
The event could not be attributed to a  specific region on the Sun
due to limited observations. The other M-class events were an M1/Sf
at 03/2351Z from 9415 (S21E60), an M1/Sf at 1027Z from 9415 again,
and an M1/Sf at 1159Z from Region 9401 (N24W70). Region 9393
(N18W90+) has rotated around the west limb. Region 9415 (S21E60) now
is the largest, most active region on the disk with an area of 680
millionths in a DKO beta-gamma configuration. A 25 degree filament
near N30E25 disappeared during the past 24 hours. Two CMEs were
observed on the east limb at 03/1950Z and 04/0950Z: corresponding
EIT images indicated back-sided sources behind the east limb.
IB.  Solar Activity Forecast:  Solar activity is expected to be
mostly moderate. There is a chance for an isolated major flare
during the next three days, with higher probabilities during the
next 24 hours while region 9393 is not too far beyond west limb.
IIA.  Geophysical Activity Summary 03/2100Z to 04/2100Z:
The geomagnetic field was quiet until a sudden impulse occurred at
1455Z. The impulse resulted from a shock in the solar wind which was
initially observed at ACE at 1422Z. After the shock the solar wind
displayed high speeds and strong fluctuations of the magnetic
component Bz (peak values were around +/- 20 nT). This disturbed
solar wind produced active to minor storm levels of geomagnetic
activity. Bz stabilized into a steady northward orientation around
1830Z and  geomagnetic activity levels seemed to be calming in
response. The shock and subsequent enhanced solar wind flow are most
likely to have been produced by the combined drivers from CMEs out
of region 9393 on April 2. The greater than 10 MeV proton event
continues to be in progress. The shock passage produced a very
slight enhancement of the particle flux levels. The flux at 04/2100Z
was 113 pfu.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at active to minor storm levels during the next 24
hours. Solar wind speeds and temperatures are still enhanced, and
there is still a possibility for more intervals of geoeffective
solar wind during the next 24 hours. The second day is forecast to
be active, based on the possible impact of a glancing blow from the
CME that originated from region 9415 on 3 April. Mostly unsettled
levels should prevail by day three.
III.  Event Probabilities 05 Apr-07 Apr
Class M    80/65/65
Class X    30/20/20
Proton     99/15/15
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           04 Apr 205
Predicted   05 Apr-07 Apr  200/190/180
90 Day Mean        04 Apr 167
V.  Geomagnetic A Indices
Observed Afr/Ap 03 Apr  005/005
Estimated Afr/Ap 04 Apr  025/020
Predicted Afr/Ap 05 Apr-07 Apr  030/030-020/025-015/015
VI.  Geomagnetic Activity Probabilities 05 Apr-07 Apr
A.  Middle Latitudes
Active                20/35/30
Minor storm           30/25/20
Major-severe storm    20/15/05
B.  High Latitudes
Active                20/35/30
Minor storm           30/15/20
Major-severe storm    25/25/05