:Product: Weekly Highlights and Forecasts
:Issued: 1999 May 25 2112 UT
HIGHLIGHTS OF SOLAR AND GEOMAGNETIC ACTIVITY
17 - 23 MAY 1999

SOLAR ACTIVITY RANGED FROM LOW TO MODERATE LEVELS. ACTIVITY WAS AT
MODERATE LEVELS ON 17 MAY WITH AN OPTICALLY UNCORRELATED M2 AT
17/0455UT AND A M1 AT 17/2202UT. THE REMAINDER OF THE PERIOD WAS AT
LOW LEVELS WITH NUMEROUS C-CLASS FLARES. THE MOST IMPRESSIVE OF
THESE WAS A LONG DURATION C2 FLARE AT 21/1949UT WHICH WAS ALSO
OPTICALLY UNCORRELATED. LASCO/SOHO IMAGES SHOWED A PARTIAL-HALO CME
EVENT DURING THIS PERIOD WHICH MAY HAVE BEEN ASSOCIATED WITH REGION
(N36, L=098, CLASS/AREA HKX/360) ON 22 MAY.

REAL-TIME SOLAR WIND DATA WERE AVAILABLE FROM THE ADVANCED
COMPOSITION EXPLORER (ACE) SPACECRAFT FOR MOST OF THE PERIOD. EARLY
IN THE PERIOD SOLAR WIND VELOCITY ROSE FROM 325 TO 720 KM/SEC,
DENSITIES INCREASED TO 65 P/CC AND IMF BZ WAS BETWEEN PLUS AND MINUS
20 NT. VELOCITIES AND DENSITY REMAINED ELEVATED UNTIL 19 MAY AND
THEN DECREASED TO BACKGROUND LEVELS FOR THE REMAINDER OF THE PERIOD.
THIS ACTIVITY WAS LIKELY RELATED TO A SHOCK PRECEDING CORONAL HOLE
INFLUENCES.

THERE WERE NO SIGNIFICANT PROTON ENHANCEMENTS DETECTED AT
GEO-SYNCHRONOUS ALTITUDES.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEO-SYNCHRONOUS ALTITUDE
REACHED MODERATE TO HIGH LEVELS DURING 21-23 MAY.

THE GEOMAGNETIC FIELD WAS DISTURBED DURING 18 MAY WITH ACTIVE LEVELS
AT MIDDLE LATITUDES AND MINOR TO MAJOR STORM LEVELS AT HIGH
LATITUDES. THE DISTURBANCE WAS RELATED TO RECURRENT CORONAL HOLE
EFFECTS. A 45 NT SUDDEN IMPULSE WAS OBSERVED ON 18 MAY AT 18/0058UT
(AS MEASURED BY THE BOULDER USGS MAGNETOMETER). ON 23 MAY QUIET TO
ACTIVE LEVELS WERE OBSERVED AT MIDDLE LATITUDES WITH MINOR STORM
LEVELS OBSERVED AT HIGH LATITUDES. THE DISTURBANCE MAY HAVE BEEN DUE
TO THE CME OBSERVED ON 21 MAY.

FORECAST OF SOLAR AND GEOMAGNETIC ACTIVITY
26 MAY - 21 JUNE 1999

SOLAR ACTIVITY IS EXPECTED TO RANGE FROM LOW TO MODERATE LEVELS.
THERE IS ALSO A FAIR CHANCE FOR AN ISOLATED MAJOR FLARE DURING THE
FIRST HALF OF JUNE WITH THE ANTICIPATED RETURN OF OLD ACTIVE REGION
8534 (S17, L=223) AND REGION 8541 (N22, L=192).

NO SIGNIFICANT PROTON FLUX ENHANCEMENTS ARE EXPECTED AT
GEO-SYNCHRONOUS ALTITUDE.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEO-SYNCHRONOUS ALTITUDE IS
EXPECTED TO BE AT  NORMAL TO MODERATE LEVELS.

GEOMAGNETIC FIELD ACTIVITY IS EXPECTED TO BE AT UNSETTLED TO ACTIVE
LEVELS AROUND 14 JUNE DUE TO CORONAL HOLE EFFECTS. QUIET TO
UNSETTLED CONDITIONS ARE EXPECTED DURING THE REST OF THE PERIOD,
BARRING ANY EARTH-DIRECTED CORONAL MASS EJECTION.

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