:Product: 19990628RSGA.txt
:Issued: 1999 Jun 28 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 179 ISSUED AT 2200Z ON 28 JUN 1999
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  27/2100Z
TO 28/2100Z:  SOLAR ACTIVITY WAS LOW. REGION 8611 (S25E47) WAS THE
MOST ACTIVE REGION ON THE DISK TODAY AND PRODUCED NUMEROUS C-CLASS
SUBFLARES. THE LARGEST OF THESE WAS A C6/1F AT 1934Z. THIS GROUP
EXHIBITED VERY BRIGHT PLAGE ALL DAY AND IS GROWING STEADILY. REGION
8598 (N22W25) IS STILL THE LARGEST SUNSPOT GROUP ON THE DISK BUT
COULD ONLY MUSTER ONE SUBFLARE, IN SPITE OF A DELTA SPOT NEAR REGION
CENTER. THIS GROUP SHOWED SIGNIFICANT DECAY OF MAGNETIC FLUX AND IS
CLEARLY ON THE DECLINE. A PARTIAL HALO CME WAS REPORTED BY LASCO
THAT WAS ASSOCIATED WITH A SIGNATURE IN EIT IN THE NORTHWEST
QUADRANT OF THE SOLAR DISK. THESE EVENTS WERE ALSO TIME COINCIDENT
WITH YESTERDAY'S M1 FLARE FROM REGION 8592 AT N23W25.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. REGIONS 8598 AND 8611 ARE THE BEST CANDIDATES FOR
PRODUCING AN ISOLATED M-CLASS EVENT OVER THE NEXT THREE DAYS.
REGIONS 8602 (N18E08), AND 8603 (S15E18) MIGHT ALSO CONTRIBUTE,
GIVEN THE CURRENT SLOW GROWTH TREND IN THESE REGIONS.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 27/2100Z TO 28/2100Z:
THE GEOMAGNETIC FIELD RANGED FROM QUIET TO MAJOR STORM LEVELS.
YESTERDAY'S ACTIVE CONDITIONS DECLINED TO QUIET AROUND 28/0000Z.
AROUND 28/0400Z THE SOLAR WIND VELOCITY BEGAN TO INCREASE
SIGNIFICANTLY, REACHING SPEEDS AS HIGH AS 900 KM/S BY 0510Z. THE
GEOMAGNETIC FIELD RESPONDED WITH A PERIOD OF MAJOR STORM FROM
0300-0600Z, FOLLOWED BY AN ACTIVE TO MINOR STORM PERIOD FROM
0600-0900Z. THE INTERPLANETARY MAGNETIC FIELD SHOWED SOME MILDLY
NEGATIVE BZ FROM 0400-0600Z BUT RETURNED TO NOMINAL LEVELS
THEREAFTER. IN RESPONSE THE GEOMAGNETIC FIELD ALSO CALMED TO QUIET
TO UNSETTLED FROM 0900Z THROUGH THE END OF THE DAY. GIVEN THE HIGH
SPEED AND VERY LOW DENSITY SEEN WITH THIS SOLAR WIND EVENT, IT IS
MOST LIKELY THAT ACE OBSERVED THE RAREFACTION REGION BEHIND THE
PARTIAL HALO CME OF 24 JUNE, WHICH WAS KNOWN TO BE DIRECTED SLIGHTLY
TO THE WEST OF THE SUN-EARTH LINE.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO BE UNSETTLED TO ACTIVE FOR THE NEXT 24 HOURS. MOSTLY
UNSETTLED CONDITIONS SHOULD DOMINATE ON THE SECOND DAY.
PREDOMINANTLY UNSETTLED LEVELS ARE ALSO EXPECTED ON THE THIRD DAY,
BUT THERE WILL BE AN ENHANCED PROBABILITY FOR SOME ACTIVE PERIODS
BECAUSE OF THE PARTIAL HALO CME OF THE 27TH.
III.  EVENT PROBABILITIES 29 JUN-01 JUL
CLASS M    55/50/45
CLASS X    05/05/05
PROTON     10/10/05
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           28 JUN 197
PREDICTED   29 JUN-01 JUL  180/175/170
90 DAY MEAN        28 JUN 144
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 27 JUN  015/021
ESTIMATED AFR/AP 28 JUN  020/025
PREDICTED AFR/AP 29 JUN-01 JUL  012/018-010/012-012/015
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 29 JUN-01 JUL
A.  MIDDLE LATITUDES
ACTIVE                25/15/20
MINOR STORM           05/05/10
MAJOR-SEVERE STORM    05/01/05
B.  HIGH LATITUDES
ACTIVE                25/15/20
MINOR STORM           05/05/15
MAJOR-SEVERE STORM    05/01/05