NOAA SEC Report of Solar-Geophysical Activity 15 April 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 15 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 105 Issued at 2200Z on 15 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  14/2100Z
to 15/2100Z:  Solar activity was high.  Region 9415 (S12W87) produced
an X14/2b flare at 15/1350 UTC.  This event had an associated Type
II, with a speed of 1000 km/s,  and Type IV radio sweeps.  It was
also accompanied by a tenflare of 48000 sfu.  A 12 degree filament
located at S23W02 disappeared between 14/2054 UTC and 15/1135 UTC.
IB.  Solar Activity Forecast:  Solar activity is expected to be low
to moderate.  Region 9415 is still capable of producing a major
flare before it rotates over the western limb.
IIA.  Geophysical Activity Summary 14/2100Z to 15/2100Z:
The geomagnetic field was unsettled to active.  The X-class event
described in Part IA produced proton events at greater than 10 and
100 MeV flux at geosynchronous orbit which are still in progress. 
The greater than 100 MeV crossed event threshold at 15/1405 UTC, and
so far have reached a peak flux of 146 pfu at 15/1525 UTC.  The
greater than 10 MeV crossed event threshold at 15/1410 UTC and has
reached a peak flux of 951 pfu at 15/1920 UTC.  A ground level event
was measured on the Thule riometer at 15/1505 UTC, and a polar cap
absorption (PCA) event began at 15/1950 UTC.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be quiet to active for April 16 and 17.  Active to minor
storm conditions are expected on April 18 as a result of the X14
mentioned in Part IA above.  Effects from a high speed coronal
stream may also be expected on April 18.  The greater than 10 MeV
proton event is expected to continue for most of the period, and the
greater than 100 MeV proton event is expected to go below threshold
by sometime on April 16.
III.  Event Probabilities 16 Apr-18 Apr
Class M    80/70/60
Class X    25/10/10
Proton     90/10/10
PCAF       in progress
IV.  Penticton 10.7 cm Flux
Observed           15 Apr 134
Predicted   16 Apr-18 Apr  145/150/160
90 Day Mean        15 Apr 166
V.  Geomagnetic A Indices
Observed Afr/Ap 14 Apr  013/015
Estimated Afr/Ap 15 Apr  015/015
Predicted Afr/Ap 16 Apr-18 Apr  015/015-015/020-020/035
VI.  Geomagnetic Activity Probabilities 16 Apr-18 Apr
A.  Middle Latitudes
Active                25/25/50
Minor storm           05/05/10
Major-severe storm    01/01/05
B.  High Latitudes
Active                30/35/60
Minor storm           10/10/15
Major-severe storm    05/05/10