:Product: 19980918RSGA.txt
:Issued: 1998 Sep 18 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 261 ISSUED AT 2200Z ON 18 SEP 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  17/2100Z
TO 18/2100Z:  SOLAR ACTIVITY WAS VERY LOW. REGION 8339 (S16E30)
EXHIBITED SOME MINOR GROWTH AND PRODUCED SEVERAL SUBFLARES DURING
THE LATTER HALF OF THE PERIOD. NO SIGNIFICANT X-RAY ENHANCEMENTS
ACCOMPANIED THESE FLARES. REGION 8340 (N22E64) IS LIKELY THE MOST
COMPLEX REGION ON THE VISIBLE DISK BUT ITS LIMB PROXIMITY IS STILL
HAMPERING A DETAILED ANALYSIS. PERIODS OF SURGING WITH SEVERAL PLAGE
FLUCTUATIONS WERE NOTED IN THIS REGION AND A SMALL FILAMENT ERUPTED
LATE IN THE PERIOD. A PROMINENCE ERUPTED OFF THE SW LIMB AT
17/2250Z. THE REMAINING REGIONS WERE QUIET.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE VERY
LOW TO LOW. THOUGH NO FLARING HAS YET OCCURRED IN REGION 8340, ITS
SIZE AND APPARENT COMPLEXITY WILL LIKELY PRODUCE ISOLATED C-CLASS
FLARING.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 17/2100Z TO 18/2100Z:
THE GEOMAGNETIC FIELD WAS QUIET UNTIL APPROXIMATELY 18/1100Z. A
DISTURBANCE BEGAN AT THAT TIME PRODUCING UNSETTLED TO ACTIVE
CONDITIONS WITH AN ISOLATED PERIOD OF MAJOR STORMING AT HIGH
LATITUDES. PREDOMINANTLY UNSETTLED TO ACTIVE CONDITIONS HAVE BEEN
OBSERVED AT ALL LATITUDES SINCE 18/1500Z.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN UNSETTLED TO ACTIVE. A LARGE EXTENSION OF THE
NORTHERN CORONAL HOLE WILL MOVE INTO FAVORABLE POSITION FOR
GEOEFFECTIVENESS BY LATE TOMORROW.  DISTURBED CONDITIONS ARE
EXPECTED TO PERSIST THROUGH THE EARLY PART OF NEXT WEEK.
III.  EVENT PROBABILITIES 19 SEP-21 SEP
CLASS M    10/15/15
CLASS X    01/01/01
PROTON     01/01/01
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           18 SEP 123
PREDICTED   19 SEP-21 SEP  125/130/130
90 DAY MEAN        18 SEP 127
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 17 SEP  005/007
ESTIMATED AFR/AP 18 SEP  017/010
PREDICTED AFR/AP 19 SEP-21 SEP  015/015-015/015-015/020
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 19 SEP-21 SEP
A.  MIDDLE LATITUDES
ACTIVE                35/35/35
MINOR STORM           10/10/10
MAJOR-SEVERE STORM    05/05/05
B.  HIGH LATITUDES
ACTIVE                45/45/45
MINOR STORM           20/25/25
MAJOR-SEVERE STORM    05/10/10