:Product: 19990918RSGA.txt
:Issued: 1999 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 1999
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  17/2100Z
TO 18/2100Z:  SOLAR ACTIVITY WAS LOW. REGION 8700 (N13E07) PRODUCED
THE LARGEST FLARE SINCE YESTERDAY, A C8/2F AT 17/2212UT. SEVERAL
SUBFLARES AND FLARE-BRIGHT PLAGE FLUCTUATIONS ALSO OCCURRED IN THIS
REGION. 8700 SUNSPOTS CONTINUE TO EXHIBIT MIXED POLARITIES. REGION
8699 (N22W65) ALSO PRODUCED C-CLASS ACTIVITY, THE LARGEST BEING A
C2/SF AT 18/1821UT. NEW REGION 8705 (S11E28) EMERGED ON THE DISK.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. C-CLASS ACTIVITY IS EXPECTED IN REGIONS 8699 AND 8700.
AN ISOLATED M-CLASS FLARE IS POSSIBLE IN REGION 8700.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 17/2100Z TO 18/2100Z:
THE GEOMAGNETIC FIELD RANGED FROM QUIET TO ACTIVE. ACTIVITY LEVELS
CONTINUED TO FLUCTUATE IN RESPONSE TO SIMILAR SOLAR WIND (HIGH SPEED
AND VARIABLE BZ) EXPERIENCED FOR THE PAST FEW DAYS. THE GREATER THAN
2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT WAS HIGH.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN QUIET TO UNSETTLED FOR THE NEXT SEVERAL HOURS.
ACTIVE TO STORM CONDITIONS ARE POSSIBLE LATE ON THE 19TH, CONTINUING
THROUGH THE 20TH, DUE TO THE CME/DSF DETECTED ON THE 16TH.  THE
GREATER THAN 2 MEV ELECTRON FLUX SHOULD REMAIN MODERATE TO HIGH.
III.  EVENT PROBABILITIES 19 SEP-21 SEP
CLASS M    15/15/15
CLASS X    01/01/01
PROTON     01/01/01
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           18 SEP 152
PREDICTED   19 SEP-21 SEP  155/160/165
90 DAY MEAN        18 SEP 164
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 17 SEP  009/015
ESTIMATED AFR/AP 18 SEP  015/015
PREDICTED AFR/AP 19 SEP-21 SEP  015/015-030/030-015/015
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 19 SEP-21 SEP
A.  MIDDLE LATITUDES
ACTIVE                50/50/30
MINOR STORM           20/30/10
MAJOR-SEVERE STORM    05/10/05
B.  HIGH LATITUDES
ACTIVE                50/50/30
MINOR STORM           20/30/10
MAJOR-SEVERE STORM    05/10/05