:Product: 20020423RSGA.txt
:Issued: 2002 Apr 23 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 113 Issued at 2200Z on 23 Apr 2002
IA.  Analysis of Solar Active Regions and Activity from  22/2100Z
to 23/2100Z:  Solar activity remained at low levels. Minor growth
occurred in Regions 9914 (N04E18), 9915 (N11E28), and 9916 (S18E47)
and each produced an isolated subflare. Region 9912 (N11W38) showed
gradual decay in its trailer spots. A large filament erupted from
the southwest quadrant during 22/2230 - 2325 UTC. A CME followed the
eruption, but it did not appear to be Earth-directed. New Regions
9920 (S23W03), 9921 (N12E41), and 9922 (N19E56) were numbered.
IB.  Solar Activity Forecast:  Solar activity is expected to be low
to moderate. There's a chance for an isolated low-level M-class
flare during the period.
IIA.  Geophysical Activity Summary 22/2100Z to 23/2100Z:
Geomagnetic field activity ranged from quiet to major storm levels.
Field activity increased to active to major storm levels during
23/0300 - 0900 UTC following a sudden impulse at 23/0450 UTC (60 nT,
as measured by the Boulder USGS magnetometer). This increase was due
to a CME passage associated with the X1 limb flare on 21 April from
old Region 9906 (S16, L = 151). Activity decreased to unsettled to
active levels during 23/0900 - 1800 UTC. The field was quiet after
23/1800 UTC. The greater than 100 MeV proton event that began at
21/0155 UTC ended at 22/2335 UTC (peak 22.9 pfu at 21/1025 UTC). The
greater than 10 MeV proton event that began at 21/0225 UTC continued
(peak 2520 pfu at 21/2320 UTC). The greater than 10 MeV flux at the
close of the period was around 110 pfu.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at unsettled to active levels on 24 April decreasing
to quiet to unsettled levels for the rest of the period. The greater
than 10 MeV proton event is expected to end on 25 April.
III.  Event Probabilities 24 Apr-26 Apr
Class M    40/40/40
Class X    05/05/05
Proton     99/80/20
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           23 Apr 175
Predicted   24 Apr-26 Apr  180/180/180
90 Day Mean        23 Apr 198
V.  Geomagnetic A Indices
Observed Afr/Ap 22 Apr  008/012
Estimated Afr/Ap 23 Apr  018/022
Predicted Afr/Ap 24 Apr-26 Apr  015/015-010/010-008/008
VI.  Geomagnetic Activity Probabilities 24 Apr-26 Apr
A.  Middle Latitudes
Active                40/30/25
Minor storm           10/05/05
Major-severe storm    05/01/01
B.  High Latitudes
Active                45/35/30
Minor storm           15/10/10
Major-severe storm    10/05/05