NOAA SEC Report of Solar-Geophysical Activity 27 Apr 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 27 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 117 Issued at 2200Z on 27 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  26/2100Z
to 27/2100Z:  Solar activity was moderate. Region 9433 (N18W39)
produced an M1/1f flare at 27/1915 UTC along with isolated C-class
subflares. Region 9433 began to gradually decay following
yesterday's M7/2b flare with decreased spot count and penumbral
coverage. However, a magnetic delta configuration persisted in the
trailer portion of the region, where most flare activity has
occurred. Region 9441 (N08E38) produced isolated subflares as it
gradually increased in spot count and penumbral coverage, though it
remained a moderate-sized, simply-structured spot group. New Region
9443 (S10E21), a small simple bipole, was numbered.
IB.  Solar Activity Forecast:  Activity is expected to be at moderate
to high levels. Region 9433 is expected to produce mostly low-level
M-class flares. However, it may produce an isolated major flare
during the period.
IIA.  Geophysical Activity Summary 26/2100Z to 27/2100Z:
Geomagnetic field activity was at quiet to unsettled levels. The
greater than 10 MeV electron flux became enhanced following
yesterdays M7/2b flare, but did not reach event levels.
IIB.  Geophysical Activity Forecast:  A geomagnetic disturbance is
expected to commence during the latter half of 28 April and continue
into 29 April following yesterday's M7/2b flare and associated
full-halo CME . Active to major storm levels will be possible during
this disturbance. Mostly unsettled levels are expected during 30
April. The greater than 10 MeV proton flux could increase to event
levels on 28 April. Region 9433 may produce a proton flare during
the period.
III.  Event Probabilities 28 Apr-30 Apr
Class M    75/75/75
Class X    20/20/20
Proton     20/20/20
PCAF       yellow
IV.  Penticton 10.7 cm Flux
Observed           27 Apr 191
Predicted   28 Apr-30 Apr  185/180/175
90 Day Mean        27 Apr 167
V.  Geomagnetic A Indices
Observed Afr/Ap 26 Apr  008/007
Estimated Afr/Ap 27 Apr  005/008
Predicted Afr/Ap 28 Apr-30 Apr  015/010-040/040-012/020
VI.  Geomagnetic Activity Probabilities 28 Apr-30 Apr
A.  Middle Latitudes
Active                25/30/40
Minor storm           20/35/20
Major-severe storm    05/10/05
B.  High Latitudes
Active                30/25/45
Minor storm           25/40/25
Major-severe storm    10/15/10