NOAA SEC Report of Solar-Geophysical Activity 20 Apr 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 20 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 110 Issued at 2200Z on 20 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  19/2100Z
to 20/2100Z:  Solar activity was moderate. The largest flare was an
M4/1F at 20/2004 UTC in Region 9433 (N17E52). This area also
produced an M1/1F at 20/0523 UTC. The region remains a
moderately-sized F-type sunspot group with some mixed polarities in
the central portions and a total area similar to yesterday's. Region
9432 (N08W06) also produced C-class subflares. Today's Penticton
F10.7 noon reading was taken during the M4, resulting in a
flare-enhanced value of 180 sfu.
IB.  Solar Activity Forecast:  Solar activity is expected to be
moderate. Additional M-class activity in Region 9433 is likely with
the possibility of an isolated major flare.
IIA.  Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field was quiet to unsettled. The greater than 10 MeV
proton event dropped below the 10 pfu event threshold at 20/1015 UTC
(start 18/0315 UTC and 321 pfu peak at 18/1045 UTC) and continues to
slowly decay.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be quiet to unsettled. A major flare in Region 9433
could generate another greater than 10 MeV proton event.
III.  Event Probabilities 21 Apr-23 Apr
Class M    75/75/75
Class X    10/10/10
Proton     05/05/05
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           20 Apr 180
Predicted   21 Apr-23 Apr  175/185/195
90 Day Mean        20 Apr 165
V.  Geomagnetic A Indices
Observed Afr/Ap 19 Apr  005/007
Estimated Afr/Ap 20 Apr  008/010
Predicted Afr/Ap 21 Apr-23 Apr  005/010-005/010-010/010
VI.  Geomagnetic Activity Probabilities 21 Apr-23 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