NOAA SEC Report of Solar-Geophysical Activity 17 Aug 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Aug 17 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 229 Issued at 2200Z on 17 Aug 2001
IA.  Analysis of Solar Active Regions and Activity from  16/2100Z
to 17/2100Z:  Solar activity was low. Only a few low-level C-class
subflares occurred. The largest was a C1/Sf at 17/0011 UTC in Region
9581 (S25W42). Although there are several sunspot groups on the
visible disk all of them are relatively small and magnetically
simple. New Regions 9586 (S15W47) and 9587 (S11E56) were numbered.
IB.  Solar Activity Forecast:  Solar activity is expected to be low.
Additional low-level C-class flares are possible.
IIA.  Geophysical Activity Summary 16/2100Z to 17/2100Z:
The geomagnetic field was quiet until the occurrence of a sudden
impulse observed at ground magnetometers (36 nT at Boulder) at about
17/1103 UTC. The impulse was preceded by a shock observed at the
NASA ACE spacecraft at 17/1017 UTC. The geomagnetic field has been
at mostly active to minor storm levels since the impulse. A series
of magnetopause crossings were observed at the NOAA GOES spacecraft
in the interval from about 17/1930--2100 UTC. The greater than 100
MeV proton event which began yesterday has ended (start 16/0105 UTC,
29 pfu peak at 16/0305 UTC, and end 17/1415 UTC). The greater than
10 MeV event remains in progress (start 16/0135 UTC and 493 pfu peak
at 16/0355 UTC). The current proton flux (17/2100 UTC) at greater
than 10 MeV is about 20 pfu and is slowly decaying.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at mostly active to minor storm levels for the next
24 hours becoming unsettled to active after that. The greater than
10 MeV proton event is expected to end by 19 August.
III.  Event Probabilities 18 Aug-20 Aug
Class M    10/10/10
Class X    01/01/01
Proton     90/30/01
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           17 Aug 145
Predicted   18 Aug-20 Aug  150/150/155
90 Day Mean        17 Aug 151
V.  Geomagnetic A Indices
Observed Afr/Ap 16 Aug  003/008
Estimated Afr/Ap 17 Aug  025/025
Predicted Afr/Ap 18 Aug-20 Aug  020/015-015/015-010/018
VI.  Geomagnetic Activity Probabilities 18 Aug-20 Aug
A.  Middle Latitudes
Active                30/20/15
Minor storm           15/05/05
Major-severe storm    05/01/01
B.  High Latitudes
Active                40/30/20
Minor storm           20/10/05
Major-severe storm    05/01/01