:Product: 20010411RSGA.txt
:Issued: 2001 Apr 11 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 101 Issued at 2200Z on 11 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  10/2100Z
to 11/2100Z:  Solar activity was moderate. A single M-class event
occurred during the period. Region 9415 (S22W27) produced an M2/1f
parallel ribbon flare at 11/1326 UTC. This event was accompanied by
Type II and IV radio sweeps, a 540 sfu 10 cm radio burst, and a
full-halo coronal mass ejection (CME). Two new regions were
numbered: 9426 (S09E40) and 9427 (S07W12).
IB.  Solar Activity Forecast:  Solar activity is expected to be at
moderate to high levels. Region 9415 can be expected to produce
another major flare during the period.
IIA.  Geophysical Activity Summary 10/2100Z to 11/2100Z:
The geomagnetic field ranged from quiet to severe storm levels. Two
discernable shocks were detected by the ACE spacecraft at
approximately 11/1300 and 11/1520 UTC. These effects were most
likely the precursors for the two earth-directed CME's produced on
9-10 April. The resulting CME's arrival at earth produced severe
geomagnetic storming during the period of 11/1500-1800 UTC. The
greater than 10 MeV proton flux was at high levels all period long,
reaching a maximum of 322 PFU near the end of the period. A polar
cap absorption (PCA) event remained in effect during the period. The
greater than 2 MeV electron flux has at high levels for the first
part of the period and then decreased to moderate levels for the
remainder of the period.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to continue at active to major storm levels during the
first day of the period. A second geomagnetic storm is expected to
arrive late on 12 April or early on 13 April UTC. This disturbance
will be the result of the full-halo CME described in Section 1A.
Brief severe storm levels at high latitudes can be expected.
Unsettled to minor storm levels are expected on 14 April as the
storm subsides. The greater than 10 MeV proton event is expected to
continue through most of the period. The PCA event is expected to
end during the latter half of the period. The greater than 2 MeV
electron flux is expected to be at mostly moderate levels during the
period.
III.  Event Probabilities 12 Apr-14 Apr
Class M    80/80/80
Class X    25/25/25
Proton     80/25/25
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           11 Apr 160
Predicted   12 Apr-14 Apr  160/160/155
90 Day Mean        11 Apr 167
V.  Geomagnetic A Indices
Observed Afr/Ap 10 Apr  007/009
Estimated Afr/Ap 11 Apr  050/060
Predicted Afr/Ap 12 Apr-14 Apr  060/090-050/050-020/025
VI.  Geomagnetic Activity Probabilities 12 Apr-14 Apr
A.  Middle Latitudes
Active                15/15/35
Minor storm           25/25/15
Major-severe storm    45/45/10
B.  High Latitudes
Active                15/25/35
Minor storm           30/30/25
Major-severe storm    50/35/15