NOAA SEC Report of Solar-Geophysical Activity 17 Apr 2001

:Product: Report of Solar-Geophysical Activity
:Issued: 2001 Apr 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 107 Issued at 2200Z on 17 Apr 2001
IA.  Analysis of Solar Active Regions and Activity from  16/2100Z
to 17/2100Z:  Solar activity has been low.  There were several
optically uncorrelated C-class events during the period.  New Region
9431 (S10E49) was numbered today.
IB.  Solar Activity Forecast:  Solar activity is expected to be low
with an isolated chance for a M-class event.
IIA.  Geophysical Activity Summary 16/2100Z to 17/2100Z:
The geomagnetic field was quiet to unsettled.  The greater than 10
MeV proton event that started on April 15 is still in progress.  The
greater than 100 proton event that began at 15/1405 UTC reached a
maximum of 146 pfu at 15/1525 UTC and ended at 17/0515 UTC.  The
polar cap absorption (PCA) event ended at 17/0315 UTC.  The greater
than 2 MeV electrons at geosynchronous orbit remained at high levels
and above threshold through the period.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be unsettled to active for April 18 and 19 as a result
of possible effects from the X14/2b event on April 15, and possible
effects from a well positioned coronal hole.  Quiet to unsettled
conditions are expected to return on April 20.  The greater than 10
MeV proton event is expected to go below threshold on April 18.
III.  Event Probabilities 18 Apr-20 Apr
Class M    60/50/50
Class X    01/01/01
Proton     01/01/01
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           17 Apr 126
Predicted   18 Apr-20 Apr  135/145/155
90 Day Mean        17 Apr 165
V.  Geomagnetic A Indices
Observed Afr/Ap 16 Apr  007/007
Estimated Afr/Ap 17 Apr  008/015
Predicted Afr/Ap 18 Apr-20 Apr  020/025-015/020-010/015
VI.  Geomagnetic Activity Probabilities 18 Apr-20 Apr
A.  Middle Latitudes
Active                50/25/20
Minor storm           10/05/05
Major-severe storm    05/01/01
B.  High Latitudes
Active                50/40/30
Minor storm           15/10/10
Major-severe storm    10/05/05