:Product: Weekly Highlights and Forecasts
:Issued: 1999 Nov 23 2112 UT
HIGHLIGHTS OF SOLAR AND GEOMAGNETIC ACTIVITY
15 - 21 NOVEMBER 1999

SOLAR ACTIVITY WAS MODERATE DURING MOST OF THE PERIOD, BUT INCREASED
TO HIGH LEVELS DURING 16 - 17 NOVEMBER. ACTIVITY INCREASED TO HIGH
LEVELS ON 16 NOVEMBER WITH FIVE LOW-LEVEL M-CLASS FLARES FROM FOUR
DIFFERENT REGIONS (SEE THE ENERGETIC EVENT LIST FOR EVENT
TIMES/SOURCES). ACTIVITY REMAINED HIGH ON 17 NOVEMBER BY VIRTUE OF
AN M7/2B FLARE AT 17/0957UT WITH ASSOCIATED TYPE II AND IV RADIO
SWEEPS AND A 390 SFU TENFLARE FROM REGION 8766 (N18, L=213,
CLASS/AREA EAC/360 ON 17 NOVEMBER). THIS  REGION HAD BEEN IN A
PERIOD OF GRADUAL DECAY WHEN THE M7/2B FLARE OCCURRED, THEN
STABILIZED ON 18 NOVEMBER AS A MEDIUM-SIZED, MAGNETICALLY COMPLEX
E-TYPE SPOT GROUP. REGION 8765 (S12, L=234, CLASS/AREA EKC/1280 ON
18 NOVEMBER) WAS THE LARGEST, MOST STRUCTURALLY COMPLEX REGION ON
THE VISIBLE DISK WITH MULTIPLE MAGNETIC DELTA CONFIGURATIONS
OBSERVED WITHIN THE GROUP. IT PRODUCED ISOLATED M-CLASS FLARES EARLY
IN THE PERIOD DURING A GRADUAL GROWTH PHASE. IT ALSO PRODUCED A
COUPLE M-CLASS FLARES ON 21 NOVEMBER AS IT ENTERED A PERIOD OF
GRADUAL DECAY, THOUGH IT REMAINED LARGE AND MAGNETICALLY COMPLEX.
REGION 8771 (S15, L=174, CLASS/AREA EAI/220 ON 21 NOVEMBER)
DEVELOPED AT A MODERATE PACE DURING 18 - 20 NOVEMBER AND PRODUCED
ISOLATED M-CLASS FLARES. THIS MEDIUM-SIZED, MIXED-POLARITY REGION
WAS STILL DEVELOPING AS THE PERIOD ENDED, BUT AT A SLOWER PACE.

REAL-TIME SOLAR WIND DATA (SWEPAM) WERE NOT AVAILABLE FROM THE
ADVANCED COMPOSITION EXPLORER (ACE) SPACECRAFT DURING 15/1600 -
18/1800UT DUE TO THE LEONIDS SHOWER. VELOCITIES BRIEFLY REACHED 600
KM/SEC ON 18 NOVEMBER, THEN GRADUALLY DECREASED DURING THE REMAINDER
OF THE PERIOD. THERE WERE PERIODS OF SUSTAINED SOUTHWARD IMF BZ
DETECTED DURING 15- 16, 19, AND 21 NOVEMBER. SOLAR SECTOR
ORIENTATION SHIFTED FROM AWAY (POSITIVE POLARITY) TO TOWARD ON 17
NOVEMBER.

A MINOR PROTON ENHANCEMENT BEGAN LATE ON 17 NOVEMBER AND ENDED EARLY
ON 20 NOVEMBER. THE ENHANCEMENT FOLLOWED THE M7/2B FLARE OF 17
NOVEMBER.

THE GREATER THAN 2 MEV ELECTRON FLUX BRIEFLY REACHED HIGH LEVELS LATE
ON 21 NOVEMBER. OTHERWISE, FLUX LEVELS VARIED FROM NORMAL TO
MODERATE LEVELS.

GEOMAGNETIC FIELD ACTIVITY RANGED FROM QUIET TO UNSETTLED LEVELS
DURING MOST OF THE PERIOD. HOWEVER, BRIEF ACTIVE TO MINOR STORM
PERIODS OCCURRED ON 16 AND 21 NOVEMBER FOLLOWING PERIODS OF
SUSTAINED SOUTHWARD IMF BZ.

FORECAST OF SOLAR AND GEOMAGNETIC ACTIVITY
24 NOVEMBER - 20 DECEMBER 1999

SOLAR ACTIVITY IS EXPECTED TO RANGE FROM LOW TO HIGH LEVELS. FREQUENT
C-CLASS FLARES ARE LIKELY. ISOLATED M-CLASS FLARES WILL BE POSSIBLE
THROUGHOUT THE PERIOD. THERE IS ALSO A CHANCE FOR AN ISOLATED MAJOR
FLARE THROUGH 28 NOVEMBER.

THERE IS A CHANCE FOR A SOLAR PROTON EVENT AT GEOSYNCHRONOUS ORBIT
THROUGH 28 NOVEMBER DUE TO THE MAJOR FLARE POTENTIAL IN REGIONS 8765
AND 8771.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ALTITUDE IS
EXPECTED TO BE AT MODERATE TO HIGH LEVELS DURING 05 - 10 DECEMBER
WITH NORMAL TO MODERATE LEVELS DURING THE REMAINDER OF THE PERIOD.

THE GEOMAGNETIC FIELD IS EXPECTED TO BE AT UNSETTLED TO MINOR STORM
LEVELS DURING 04 - 08 DECEMBER DUE TO RECURRENT CORONAL HOLE
EFFECTS. OTHERWISE, ACTIVITY IS EXPECTED TO VARY BETWEEN QUIET AND
UNSETTLED LEVELS (BARRING ANY EARTH-DIRECTED CORONAL MASS
EJECTIONS).


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