:Product: 19991224RSGA.txt
:Issued: 1999 Dec 24 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 358 ISSUED AT 2200Z ON 24 DEC 1999
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  23/2100Z
TO 24/2100Z:  SOLAR ACTIVITY WAS LOW. NUMEROUS C-CLASS FLARES WERE
OBSERVED DURING THE PAST 24 HOURS. MOST OF THESE WERE FROM REGIONS
8798 (S13W73) AND 8806 (N20W14). THE LARGEST EVENT WAS A C8 AT 0934Z
WHICH WAS NOT SEEN OPTICALLY. GOOD QUALITY OBSERVATIONS TODAY
CONFIRM THE PRESENCE OF A DELTA CONFIGURATION IN THE CENTRAL PORTION
OF REGION 8806, AN AREA OF STRONG AND APPARENTLY SHEARED MAGNETIC
FIELDS. HOWEVER, THERE WERE NOT ANY DRAMATIC CHANGES OBSERVED IN
THIS GROUP. AN ERUPTIVE PROMINENCE WAS OBSERVED FROM WEST LIMB AT
N22 BETWEEN 1430-1511Z AND WAS ASSOCIATED WITH A C1 X-RAY EVENT. NEW
REGION 8809 (N21E67) ROTATED INTO VIEW TODAY. LASCO DIFFERENCE IMAGE
ANALYSIS OF THE CME ACTIVITY ON 22 DECEMBER SHOWS EVIDENCE OF A
FAINT, 360 DEGREE HALO FOR BOTH EVENTS. THE BULK OF THE MATERIAL
FROM BOTH CME'S APPEARED TO BE DIRECTED NORTHWARDS, IMPLYING ONLY A
SMALL COMPONENT OF THE CME VELOCITY IN THE EARTHWARD DIRECTION.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. REGION 8806 IS LIKELY TO PRODUCE AT LEAST AN M-CLASS
EVENT. THERE CONTINUES TO BE SOME CHANCE FOR A MAJOR FLARE OR PROTON
PRODUCING FLARE FROM THE REGION SOMETIME OVER THE NEXT THREE DAYS.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 23/2100Z TO 24/2100Z:
THE GEOMAGNETIC FIELD WAS MOSTLY QUIET. HOWEVER, A PERIOD OF
UNSETTLED TO ACTIVE CONDITIONS WAS OBSERVED FROM 0600-1200Z. THE
INCREASE WAS ASSOCIATED WITH A REVERSAL OF THE INTERPLANETARY SECTOR
MAGNETIC POLARITY FROM A TOWARDS TO AN AWAY CONFIGURATION.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO BE MOSTLY UNSETTLED OVER THE NEXT TWO DAYS, BUT THERE IS
A CHANCE FOR SOME ACTIVE PERIODS, ESPECIALLY IF THE CME'S OF 22
DECEMBER SHOULD HAPPEN TO HIT EARTH WITH A GLANCING BLOW. QUIET TO
UNSETTLED CONDITIONS ARE EXPECTED ON THE THIRD DAY.
III.  EVENT PROBABILITIES 25 DEC-27 DEC
CLASS M    70/70/70
CLASS X    15/15/15
PROTON     15/15/15
PCAF       YELLOW
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           24 DEC 182
PREDICTED   25 DEC-27 DEC  180/175/170
90 DAY MEAN        24 DEC 174
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 23 DEC  002/005
ESTIMATED AFR/AP 24 DEC  009/007
PREDICTED AFR/AP 25 DEC-27 DEC  010/015-012/020-005/010
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 25 DEC-27 DEC
A.  MIDDLE LATITUDES
ACTIVE                30/30/10
MINOR STORM           15/15/05
MAJOR-SEVERE STORM    05/05/01
B.  HIGH LATITUDES
ACTIVE                35/35/35
MINOR STORM           15/15/05
MAJOR-SEVERE STORM    05/05/01