:Product: 19980427RSGA.txt
:Issued: 1998 Apr 27 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 117 ISSUED AT 2200Z ON 27 APR 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  26/2100Z
TO 27/2100Z:  SOLAR ACTIVITY BECAME HIGH. REGION 8210 (S17E43)
PRODUCED AN X1/2B AT 27/0920Z WITH A STRONG TYPE IV AND 950 SFU
BURST AT 2695 MHZ. THIS MODERATE DURATION EVENT WAS ACCOMPANIED BY A
CORONAL MORETON WAVE AND HALO CORONAL MASS EJECTION. REGION 8210
REMAINED A SMALL-MODERATE SIZE C-CLASS GROUP. HOWEVER, A MAGNETIC
DELTA CONFIGURATION FORMED IN THE NORTHERN PORTION OF THE REGION AND
LOCALIZED MAGNETIC GRADIENTS WERE HIGH. SMALL REGIONS WERE VISIBLE
NEARING THE NORTHEAST AND SOUTHEAST LIMBS.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY SHOULD BE LOW TO
OCCASIONALLY MODERATE WITH REGION 8210 THE PROBABLE SOURCE REGION.
OBVIOUSLY, X-CLASS EVENTS ARE POSSIBLE BUT NOT CONSIDERED LIKELY DUE
TO THE SMALL AREAL COVERAGE OF THIS REGION IN WHITE LIGHT. CONTINUED
INCREASES IN MAGNETIC COMPLEXITY COULD MODIFY THIS FORECAST.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 26/2100Z TO 27/2100Z:
THE GEOMAGNETIC FIELD RANGED FROM UNSETTLED TO MINOR STORM LEVELS.
THE MOST DISTURBED PERIOD WAS FROM 27/0000-0300Z. THIS DISTURBANCE
APPEARS TO BE CAUSED BY AN EXTENSION OF THE SOUTHERN POLAR CORONAL
HOLE. ENERGETIC ELECTRON FLUXES AT GEOSYNCHRONOUS ORBIT WERE
PREDOMINANTLY HIGH.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD SHOULD BE
UNSETTLED TO SLIGHTLY ACTIVE ON 28 APR AS THE END OF THE CORONAL
HOLE STREAM ROTATES PAST THE EARTH DURING THAT PERIOD. UNSETTLED TO
MINOR STORM CONDITIONS ARE PREDICTED FOR 29-30 APR IN RESPONSE TO
THE X1 FLARE AND HALO CME MENTIONED ABOVE. ISOLATED PERIODS OF MAJOR
STORMING ARE POSSIBLE AT HIGH LATITUDES. THE ARRIVAL TIME FOR THIS
DISTURBANCE IS SOMEWHAT ADVANCED FROM PREVIOUS HALO CMES DUE TO A
HIGH LAUNCH SPEED OBSERVED NEAR THE SUN.
III.  EVENT PROBABILITIES 28 APR-30 APR
CLASS M    20/20/20
CLASS X    15/15/15
PROTON     10/15/15
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           27 APR 091
PREDICTED   28 APR-30 APR  092/094/096
90 DAY MEAN        27 APR 104
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 26 APR  021/031
ESTIMATED AFR/AP 27 APR  015/020
PREDICTED AFR/AP 28 APR-30 APR  010/015-020/020-020/020
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 28 APR-30 APR
A.  MIDDLE LATITUDES
ACTIVE                20/30/35
MINOR STORM           10/20/25
MAJOR-SEVERE STORM    05/10/10
B.  HIGH LATITUDES
ACTIVE                25/35/35
MINOR STORM           15/25/30
MAJOR-SEVERE STORM    05/15/15