:Product: 19981220RSGA.txt
:Issued: 1998 Dec 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 354 ISSUED AT 2200Z ON 20 DEC 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  19/2100Z
TO 20/2100Z:  SOLAR ACTIVITY WAS MODERATE. REGION 8415 (N20E38)
PRODUCED AN M1/1N FLARE AT 20/0900Z THAT WAS ACCOMPANIED BY MINOR
RADIO BURSTS. THIS REGION ALSO PRODUCED SEVERAL LOW TO MID C-CLASS
EVENTS DURING THE PERIOD. MIXED MAGNETIC POLARITIES REMAINED IN THIS
REGION BUT AREAL COVERAGE IN WHITE LIGHT DECREASED SLIGHTLY. A SMALL
CLASS C SUNSPOT GROUP ROTATED ONTO THE DISK NEAR N18E67 AND WAS
NUMBERED AS NEW REGION 8416. TWO LESSER REGIONS EMERGED ON THE DISK.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY SHOULD BECOME GENERALLY
LOW FOR THE NEXT THREE DAYS. REGION 8415 IS CAPABLE OF PRODUCING
ISOLATED M-CLASS EVENTS.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 19/2100Z TO 20/2100Z:
THE GEOMAGNETIC FIELD WAS PREDOMINANTLY UNSETTLED. DURING THE PERIOD,
SOLAR WIND VELOCITY INCREASED, DENSITY DECREASED, AND SEVERAL
INTERVALS OF PROLONGED SOUTHWARD BZ WERE OBSERVED.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
FORECAST TO BE QUIET TO UNSETTLED UNTIL THE LATTER HALF OF 21 DEC
WHEN A DISTURBANCE IS EXPECTED TO BEGIN. GENERALLY UNSETTLED TO
ACTIVE LEVELS ARE EXPECTED FROM THAT TIME THROUGH THE END OF 22 DEC.
DURING THIS DISTURBANCE, PERIODS OF MINOR STORMING ARE POSSIBLE AT
ALL LATITUDES WITH ISOLATED INTERVALS OF MAJOR STORMING POSSIBLE AT
HIGH LATITUDES.
III.  EVENT PROBABILITIES 21 DEC-23 DEC
CLASS M    50/40/40
CLASS X    05/05/05
PROTON     05/05/05
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           20 DEC 135
PREDICTED   21 DEC-23 DEC  130/128/129
90 DAY MEAN        20 DEC 133
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 19 DEC  006/007
ESTIMATED AFR/AP 20 DEC  012/012
PREDICTED AFR/AP 21 DEC-23 DEC  018/020-025/025-012/009
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 21 DEC-23 DEC
A.  MIDDLE LATITUDES
ACTIVE                30/30/20
MINOR STORM           20/20/05
MAJOR-SEVERE STORM    20/20/01
B.  HIGH LATITUDES
ACTIVE                25/25/20
MINOR STORM           25/25/05
MAJOR-SEVERE STORM    30/30/01