:Product: 20020421RSGA.txt
:Issued: 2002 Apr 21 2200 UTC
# 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 111 Issued at 2200Z on 21 Apr 2002
IA.  Analysis of Solar Active Regions and Activity from  20/2100Z
to 21/2100Z:  Solar activity has been high. Region 9906 (S14W90)
produced a long-duration  X1/1f flare at 0151 UTC which was
accompanied by strong radio bursts, type II and type IV radio
sweeps, and a partial halo CME. The CME moved extremely rapidly in
the plane of the sky with a projected velocity of 2400-2500 km/s.
The front of the CME appeared to be moving away from the west limb
and therefore approximately perpendicular to the line of sight. The
remainder of today's activity consisted of a few C-class events. A
filament was observed to lift off the northeast part of the disk at
21/0012 UTC and was associated with a narrow CME from the northeast
limb. Region 9912 (N10W12) has continued to grow and is currently
the largest group on the disk now that 9906 has rotated behind west
limb. 9912 was stable and quiet. Two new regions were assigned
today: 9915 (N11E54) and 9916 (S17E71).
IB.  Solar Activity Forecast:  Solar activity is expected to be low
to moderate. Region 9906 could contribute an M-class event during
the next 24 hours, but will become less of a threat as it moves
further behind the limb. There is a slight chance for an isolated
M-class event from Region 9912.
IIA.  Geophysical Activity Summary 20/2100Z to 21/2100Z:
The geomagnetic field was quiet to unsettled during the past 24
hours. A greater than 100 MeV proton event began at 21/0155 UTC in
response to the X1 flare and continues in progress. The maximum flux
observed so far was 23 PFU at 21/1025 UTC.  A greater than 10 MeV
proton event began at 21/0225 UTC and also continues in progress.
The maximum flux at greater than 10 MeV was 2210 PFU at 21/1315 UTC.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be quiet to unsettled for most of tomorrow. However, an
increase is expected late on the 22nd due to a glancing blow from
today's partial halo CME. Conditions are expected to attain mostly
active with some minor storm periods at high latitudes. There is a
slight chance, however, for minor to major storm intervals if the
CME should prove to be extraordinarily wide. Conditions should
return to unsettled to active by the 24th. The greater than 10 MeV
proton event should continue for at least 48 hours and the greater
than 100 MeV proton event is expected to continue for the next 12-24
hours.
III.  Event Probabilities 22 Apr-24 Apr
Class M    35/25/20
Class X    10/05/05
Proton     99/99/20
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           21 Apr 173
Predicted   22 Apr-24 Apr  170/175/180
90 Day Mean        21 Apr 200
V.  Geomagnetic A Indices
Observed Afr/Ap 20 Apr  030/062
Estimated Afr/Ap 21 Apr  007/007
Predicted Afr/Ap 22 Apr-24 Apr  015/015-025/030-015/020
VI.  Geomagnetic Activity Probabilities 22 Apr-24 Apr
A.  Middle Latitudes
Active                35/45/35
Minor storm           20/25/20
Major-severe storm    15/20/15
B.  High Latitudes
Active                25/30/25
Minor storm           25/30/25
Major-severe storm    20/25/20