NOAA SEC Report of Solar-Geophysical Activity 19 Apr 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 19 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 109 Issued at 2200Z on 19 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  18/2100Z
to 19/2100Z:  Solar activity was moderate due to an M2 x-ray flare at
19/1135 UTC. An optical flare report was not received but SOHO/EIT
difference images suggest the source was Region 9433 (N17E64), the
return of old 9393. All of this region appears to have rotated onto
the disk and is presently seen as a moderately-sized (700
millionths) F-type sunspot group with some mixed polarities. This
area also produced a few small C-class subflares during the day.
Interestingly, a CME was visible entering the SOHO/LASCO/C2 field of
view over the northwest limb shortly after the M2 at about 19/1200
UTC. The location suggests that departed Region 9415 was involved
with this activity but any connection to the M2 discussed above may
only be coincidental.  Regions 9434 (N19W23) and 9435 (S21E28) were
numbered.
IB.  Solar Activity Forecast:  Solar activity is expected to be low
to moderate. Region 9433 is expected to continue to produce C-class
flares and appears capable of additional M-class activity.
IIA.  Geophysical Activity Summary 18/2100Z to 19/2100Z:
The geomagnetic field has been quiet to unsettled. The greater than
100 MeV proton event ended at 19/0325 UTC (start 18/0315 UTC, 12 pfu
peak at 18/0600 UTC). The polar cap absorption (PCA) event has also
ended (19/1400 UTC). The greater than 10 MeV proton event continues
in progress (start 18/0315 UTC, 321 pfu peak at 18/1045 UTC, and
current flux about 15 pfu at 19/2100 UTC) and is slowly decaying.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to continue at quiet to unsettled levels. The greater than
10 MeV proton event is expected to drop below event threshold
sometime tomorrow (April 20 UTC).
III.  Event Probabilities 20 Apr-22 Apr
Class M    50/50/50
Class X    05/05/05
Proton     95/01/01
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           19 Apr 145
Predicted   20 Apr-22 Apr  155/165/175
90 Day Mean        19 Apr 165
V.  Geomagnetic A Indices
Observed Afr/Ap 18 Apr  022/050
Estimated Afr/Ap 19 Apr  010/008
Predicted Afr/Ap 20 Apr-22 Apr  010/010-010/010-010/010
VI.  Geomagnetic Activity Probabilities 20 Apr-22 Apr
A.  Middle Latitudes
Active                10/10/10
Minor storm           05/05/05
Major-severe storm    01/01/01
B.  High Latitudes
Active                15/15/15
Minor storm           10/10/10
Major-severe storm    01/01/01