:Product: 19990912RSGA.txt
:Issued: 1999 Sep 12 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 255 ISSUED AT 2200Z ON 12 SEP 1999
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  11/2100Z
TO 12/2100Z:  SOLAR ACTIVITY INCREASED, BUT REMAINED IN THE LOW
CATEGORY. REGION 8699 (N21E15) GREW RAPIDLY DURING THE PERIOD AND
PRODUCED NUMEROUS SUBFLARES, A FEW OF WHICH REACHED C-CLASS. THIS
REGION DISPLAYED A MODERATELY COMPLEX MAGNETIC STRUCTURE, POSSIBLY
INCLUDING A DELTA MAGNETIC CONFIGURATION. REGION 8692 (S26E11)
SHOWED SOME POLARITY MIXING, BUT WAS STABLE MUCH OF THE PERIOD. IT
PRODUCED A SUBFLARE LATE IN THE DAY. A 20-DEGREE FILAMENT, LAST SEEN
CENTERED AT S20W31, ERUPTED EARLY IN THE PERIOD. A CORONAL MASS
EJECTION FOLLOWED THE ERUPTION, BUT DID NOT APPEAR TO BE
EARTH-DIRECTED. NEW REGION 8700 (N12E81) WAS NUMBERED.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE AT
LOW TO MODERATE LEVELS. REGION 8699 MAY PRODUCE M-CLASS FLARES,
PARTICULARLY IF ITS PRESENT RATE OF GROWTH CONTINUES. THERE IS ALSO
A SLIGHT CHANCE FOR A MAJOR FLARE FROM THIS REGION.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 11/2100Z TO 12/2100Z:
GEOMAGNETIC FIELD ACTIVITY INCREASED TO QUIET TO MINOR STORM LEVELS
WITH BRIEF MAJOR STORM PERIODS DETECTED AT HIGH LATITUDES. THE ACE
SPACECRAFT DETECTED AN INTERPLANETARY SHOCK PASSAGE AT L1 AT
12/0322Z FOLLOWED BY A SUDDEN IMPULSE AT EARTH AT 12/0400Z (21 NT,
AS MEASURED BY THE BOULDER USGS MAGNETOMETER). THIS ACTIVITY IS
LIKELY DUE TO A RECURRENT HIGH-SPEED CORONAL HOLE WIND STREAM.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  GEOMAGNETIC FIELD ACTIVITY IS
EXPECTED TO RANGE FROM UNSETTLED TO MINOR STORM LEVELS THROUGH THE
PERIOD AS CORONAL HOLE EFFECTS CONTINUE. THE GREATER THAN 2 MEV
ELECTRON FLUX, CURRENTLY AT NORMAL LEVELS, IS EXPECTED TO INCREASE
TO HIGH LEVELS DURING THE PERIOD.
III.  EVENT PROBABILITIES 13 SEP-15 SEP
CLASS M    40/40/40
CLASS X    10/10/10
PROTON     10/10/10
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           12 SEP 141
PREDICTED   13 SEP-15 SEP  150/155/160
90 DAY MEAN        12 SEP 164
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 11 SEP  008/010
ESTIMATED AFR/AP 12 SEP  018/015
PREDICTED AFR/AP 13 SEP-15 SEP  018/013-018/015-018/015
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 13 SEP-15 SEP
A.  MIDDLE LATITUDES
ACTIVE                40/40/40
MINOR STORM           15/15/15
MAJOR-SEVERE STORM    05/05/05
B.  HIGH LATITUDES
ACTIVE                45/45/45
MINOR STORM           20/20/20
MAJOR-SEVERE STORM    06/06/06