:Product: 0420RSGA.txt
:Issued: 2012 Apr 20 2200 UTC
# Prepared jointly by the U.S. Dept. of Commerce, NOAA,
# Space Weather Prediction Center and the U.S. Air Force.
#
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 111 Issued at 2200Z on 20 Apr 2012
IA.  Analysis of Solar Active Regions and Activity from  19/2100Z
to 20/2100Z:  Solar activity was low. New Region 1465 (S17E39 -
Dao/beta) emerged early in the period and showed significant growth.
It produced occasional C-class flares including a C1/1f
parallel-ribbon flare at 20/1501Z. Regions 1459 (S16E01 - Dai/beta),
1460 (N15W15 - Dkc/beta), and 1462 (S25W46 - Dho/beta) also showed
significant growth during the period. Region 1462 produced an
isolated C-class flare as it grew. There were no Earth-directed CMEs
during the period.
IB.  Solar Activity Forecast:  Solar activity is expected to be low
through the period (21 - 23 April) with a chance for an isolated
M-class flare.
IIA.  Geophysical Activity Summary 19/2100Z to 20/2100Z:
Geomagnetic activity was at quiet to unsettled levels with brief
active periods at high latitudes. ACE solar wind data indicated the
minor increase in activity was due to a solar sector boundary
crossing (SSBC) at approximately 20/0700Z. The SSBC was associated
with increased IMF Bt (maximum 8 nT at 20/1059Z) and a period of
sustained southward IMF Bz (maximum deflections to -7 nT around
20/0400Z).
IIB.  Geophysical Activity Forecast:  Geomagnetic field activity is
expected to be at quiet levels during the first half of day 1 (21
April). Activity is forecast to increase to unsettled levels with a
chance for active levels beginning around 21/1500Z and continuing
into day 3 (23 April) due to expected glancing blows from the
partial-halo CMEs observed on 18 and 19 April. There will also be a
slight chance for minor storm levels on day 1.
III.  Event Probabilities 21 Apr-23 Apr
Class M    30/30/30
Class X    01/01/01
Proton     01/01/01
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           20 Apr 142
Predicted   21 Apr-23 Apr  150/150/150
90 Day Mean        20 Apr 112
V.  Geomagnetic A Indices
Observed Afr/Ap 19 Apr  005/005
Estimated Afr/Ap 20 Apr  007/007
Predicted Afr/Ap 21 Apr-23 Apr  014/015-011/012-010/012
VI.  Geomagnetic Activity Probabilities 21 Apr-23 Apr
A.  Middle Latitudes
Active                25/20/20
Minor storm           10/05/05
Major-severe storm    01/01/01
B.  High Latitudes
Active                30/25/25
Minor storm           15/10/10
Major-severe storm    05/01/01