:Product: 19980504RSGA.txt
:Issued: 1998 May 04 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
::::::::::  CORRECTED COPY  ::::::::::
SDF NUMBER 124 ISSUED AT 2200Z ON 04 MAY 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  03/2100Z
TO 04/2100Z:  SOLAR ACTIVITY HAS BEEN MODERATE FOR THE PAST 24 HOURS.
AT 03/2129Z AN M1/1B TENFLARE (810 FLUX UNITS, 8 MINUTES DURATION)
ACCOMPANIED
BY A MAJOR TYPE IV SWEEP, WAS ASSOCIATED WITH A 1B FLARE IN REGION
8210 (S17W50) AND A SIMULTANEOUS SUBFAINT FLARE IN REGION 8214
(N27E18). SYMPATHETIC FLARING HAS BEEN A CHARACTERISTIC OF THESE TWO
WIDELY SEPARATED REGIONS FOR THE PAST SEVERAL DAYS. REGION 8210 HAS
FRAGMENTED AND SHOWN CONSIDERABLE DECAY, BUT REGION 8214 IS STILL
GROWING IN WHITE LIGHT ALTHOUGH IT HAS NOT DEVELOPED THE MAGNETIC
COMPLEXITY USUALLY ASSOCIATED WITH ENERGETIC EVENTS. AN ACTIVE
PROMINENCE ON THE SOUTHEAST LIMB WAS OBSERVED, BUT THE REMAINDER OF
THE DISK AND LIMBS WERE QUIET.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE
MODERATE BASED ON THE COMBINED FLARE POTENTIAL IN REGIONS 8210 AND
8214. THE PROBABILITY OF X-CLASS ACTIVITY HAS LESSENED WITH THE
RECENT SIMPLIFICATION OF REGION 8210, BUT ADDITIONAL GROWTH IN
REGION 8214 COULD BE A PRECURSOR TO NEW MAJOR EVENTS.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 03/2100Z TO 04/2100Z:
GEOMAGNETIC ACTIVITY HAS RANGED FROM UNSETTLED TO SEVERE STORM LEVELS
FOR THE PAST 24 HOURS. THIS DISTURBANCE IS ASSUMED TO BE RELATED TO
COMPLEX SOLAR WIND STRUCTURES ASSOCIATED WITH A SERIES OF ENERGETIC
SOLAR EVENTS BEGINNING ON 29 APRIL, AND ESPECIALLY AN X1 X-RAY EVENT
THAT REACHED MAXIMUM 02/1342 UT. A SHOCK PASSED THE ACE SPACECRAFT
AT APPROXIMATELY 04/0229 UT THAT WAS OBSERVED AT EARTH APPROXIMATELY
30 MINUTES LATER. THEREAFTER, A TWO-HOUR PERIOD OF VERY STRONG
(ABOUT 40 NT) SOUTHWARD SOLAR WIND MAGNETIC FIELD WAS OBSERVED,
RESULTING IN K INDICES OF 8 IN BOULDER BETWEEN 03-09 UT AND REPORTS
OF AURORAL SIGHTINGS IN THE NORTHERN UNITED STATES. THE ENERGETIC
PROTON EVENT THAT BEGAN ON 02/1405 ENDED 04/0310 UT.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  GEOMAGNETIC ACTIVITY IS
EXPECTED TO EXPERIENCE PERIODS AT STORM LEVELS FOR THE NEXT 24
HOURS. WHILE IT IS CLEAR THAT THE LEADING PORTION OF THE CORONAL
MASS EJECTION ASSOCIATED WITH THE X1 FLARE HAS ARRIVED, IT IS NOT
CERTAIN WHETHER THE CORE OF THE EJECTION WILL YET ARRIVE. THEREFORE,
STORM LEVEL WARNINGS ARE ADVISED THROUGH 5 MAY. THE DISTURBANCE IS
EXPECTED TO END BY 7 MAY UNLESS NEW SOLAR EVENTS OCCUR.
III.  EVENT PROBABILITIES 05 MAY-07 MAY
CLASS M    50/50/50
CLASS X    10/10/10
PROTON     10/10/10
PCAF       YELLOW
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           04 MAY 121
PREDICTED   05 MAY-07 MAY  135/140/145
90 DAY MEAN        04 MAY 105
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 03 MAY  037/057
ESTIMATED AFR/AP 04 MAY  086/100
PREDICTED AFR/AP 05 MAY-07 MAY  050/060-025/045-010/025
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 05 MAY-07 MAY
A.  MIDDLE LATITUDES
ACTIVE                10/30/20
MINOR STORM           20/25/05
MAJOR-SEVERE STORM    60/20/01
B.  HIGH LATITUDES
ACTIVE                10/30/50
MINOR STORM           25/30/20
MAJOR-SEVERE STORM    65/20/05