:Product: 19981221RSGA.txt
:Issued: 1998 Dec 21 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 355 ISSUED AT 2200Z ON 21 DEC 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  20/2100Z
TO 21/2100Z:  SOLAR ACTIVITY WAS LOW. THE LARGEST EVENT OF THE PERIOD
WAS AN OPTICALLY UNCORRELATED C5 FLARE AT 21/0429Z. REGION 8416
(N19E59) PRODUCED A C2/SF AT 21/1334Z. THIS REGION IS A SMALL E
CLASS GROUP, POSSIBLY WITH MIXED POLARITIES. REGION 8415 (N20E24)
EXHIBITED CONTINUED SLOW DECAY BUT RETAINED ITS BETA GAMMA MAGNETIC
CLASSIFICATION. THIS REGION PRODUCED A C1/SF AT 21/1941Z. THE LARGE
FILAMENT IN SPOTLESS PLAGE REGION 8414 (N26W10) WAS GENERALLY QUIET
BUT SHOWED SLOW DENSIFICATION DURING THE PERIOD.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY SHOULD REMAIN AT
PREDOMINANTLY LOW LEVELS. REGION 8415 RETAINS THE CAPABILITY OF
PRODUCING AN ISOLATED M-CLASS EVENT, BUT THAT POSSIBILITY IS WANING
WITH THE DECAY IN THE REGION. REGION 8414 MAY PRODUCE A LONG
DURATION X-RAY EVENT SHOULD THE LARGE FILAMENT ERUPT. SHOULD THIS
OCCUR, A LARGE CORONAL MASS EJECTION WOULD LIKELY RESULT.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 20/2100Z TO 21/2100Z:
THE GEOMAGNETIC FIELD WAS QUIET. AT THIS TIME, THE EXPECTED SHOCK
FROM THE HALO CORONAL MASS EJECTION ON 18 DEC HAS NOT ARRIVED.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD SHOULD
BECOME DISTURBED ON 22 DEC. GENERALLY UNSETTLED TO ACTIVE CONDITIONS
ARE EXPECTED ON THAT DAY. PERIODS OF MINOR AND POSSIBLY MAJOR
STORMING ARE POSSIBLE SHOULD THAT DISTURBANCE ARRIVE AS EXPECTED.
QUIET TO UNSETTLED GEOMAGNETIC CONDITIONS ARE FORECAST FOR 23-24
DEC.
III.  EVENT PROBABILITIES 22 DEC-24 DEC
CLASS M    40/35/30
CLASS X    05/05/05
PROTON     05/05/05
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           21 DEC 135
PREDICTED   22 DEC-24 DEC  132/135/138
90 DAY MEAN        21 DEC 133
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 20 DEC  009/011
ESTIMATED AFR/AP 21 DEC  005/010
PREDICTED AFR/AP 22 DEC-24 DEC  025/018-012/009-008/009
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 22 DEC-24 DEC
A.  MIDDLE LATITUDES
ACTIVE                25/20/10
MINOR STORM           20/10/05
MAJOR-SEVERE STORM    20/05/01
B.  HIGH LATITUDES
ACTIVE                25/20/15
MINOR STORM           25/10/05
MAJOR-SEVERE STORM    30/05/01