:Product: 19980420RSGA.txt
:Issued: 1998 Apr 20 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 110 ISSUED AT 2200Z ON 20 APR 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  19/2100Z
TO 20/2100Z:  SOLAR ACTIVITY BECAME MODERATE. A LONG DURATION M1
X-RAY EVENT AND TYPE II SWEEP OCCURRED AT 20/1021UT. THE LIKELY
SOURCE FOR THE FLARE WAS BEHIND THE SW LIMB. SPACE-BASED SENSORS
INDICATE STRONG EMISSIONS ON THE LIMB ALONG S25. A LARGE CME WAS
ALSO OBSERVED OFF THE W-SW LIMB. FAINT POST FLARE LOOPS WERE ALSO
EVIDENT. REGION 8205 (N21W40) CHANGED VERY LITTLE IN THE PAST 24
HOURS, AND MAINTAINS IT'S DSO BETA CONFIGURATION. THE REMAINING
REGIONS HAVE BEEN QUIET.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE VERY
LOW TO LOW. REGION 8205 HAS SMALL POTENTIAL TO PRODUCE A C-CLASS
FLARE. FURTHER ACTIVITY ALONG THE SW LIMB IS POSSIBLE BUT UNLIKELY
AS POSSIBLE SOURCE REGION ROTATES FURTHER BEHIND THE LIMB.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 19/2100Z TO 20/2100Z:
THE GEOMAGNETIC FIELD WAS QUIET TO ACTIVE. A GREATER THAN 10 MEV
PROTON EVENT BEGAN AT 20/1130Z, PASSED THE 10 PFU THRESHOLD AT
20/1400Z, AND IS CURRENTLY STEADY AT A MAXIMUM OF 330 PFU. THE
GREATER THAN 100 MEV PROTON FLUX IS AT 2.3 PFU AND STILL RISING
SLOWLY. POLAR CAP ABSORPTION IS CURRENTLY AT A MAXIMUM OF 6.4 DB.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO CONTINUE AT QUIET TO ACTIVE LEVELS. MOST OF THE MATERIAL
FROM THIS MORNING'S ACTIVITY APPEARS WESTWARD BOUND, THUS, NO
SIGNIFICANT IMPACT IS EXPECTED ON THE GEOMAGNETIC FIELD. THE 10 AND
100 MEV PROTON EVENTS ARE EXPECTED TO CONTINUE THROUGH TOMORROW.
III.  EVENT PROBABILITIES 21 APR-23 APR
CLASS M    10/05/05
CLASS X    01/01/01
PROTON     10/05/01
PCAF       IN PROGRESS
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           20 APR 098
PREDICTED   21 APR-23 APR  096/094/092
90 DAY MEAN        20 APR 104
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 19 APR  002/004
ESTIMATED AFR/AP 20 APR  010/012
PREDICTED AFR/AP 21 APR-23 APR  010/010-012/012-010/012
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 21 APR-23 APR
A.  MIDDLE LATITUDES
ACTIVE                15/25/25
MINOR STORM           05/10/10
MAJOR-SEVERE STORM    01/05/05
B.  HIGH LATITUDES
ACTIVE                20/30/30
MINOR STORM           05/15/10
MAJOR-SEVERE STORM    05/11/11