:Product: Weekly Highlights and Forecasts
:Issued: 1999 Sep 14 2112 UT
HIGHLIGHTS OF SOLAR AND GEOMAGNETIC ACTIVITY
06 - 12 SEPTEMBER 1999

SOLAR ACTIVITY RANGED FROM VERY LOW TO MODERATE LEVELS. REGION 8690
(N13, L=119, CLASS/AREA DSO/050 ON 08 SEPTEMBER) PRODUCED AN M1/1B
FLARE AT 08/1217UT. THIS WAS THE ONLY MODERATE ACTIVITY DURING THE
PERIOD. ACTIVITY FOR THE REST OF THE PERIOD WAS VERY LOW TO LOW.
REGION 8690 PRODUCED MOST THE ACTIVITY, HOWEVER REGIONS 8692 (S27,
L=009, CLASS/AREA EAO/270 ON 12 SEPTEMBER) AND 8699 (N21, L=003,
CLASS/AREA DRO/030 ON 12 SEPTEMBER) SHOWED RAPID GROWTH AND
INCREASED MAGNETIC COMPLEXITY AT THE END OF THE PERIOD.

REAL-TIME SOLAR WIND DATA WERE AVAILABLE FROM THE ADVANCED
COMPOSITION EXPLORER (ACE) SPACECRAFT FOR MOST OF THE PERIOD. WIND
SPEEDS FLUCTUATED BETWEEN 320 TO 550 KM/SEC. IMF BZ FLUCTUATED
BETWEEN NORTHWARD AND SOUTHWARD FOR MOST OF THE WEEK. BZ WAS
PREDOMINATELY SOUTHWARD ON 12 SEPTEMBER WITH MAXIMUM SOUTHERLY
DEFLECTIONS FROM MINUS 07 TO MINUS 10 NT. ACE REAL-TIME SOLAR WIND
MEASUREMENTS INDICATED THE ARRIVAL OF A HIGH SPEED, LOW DENSITY
SOLAR WIND STREAM AT ABOUT 07/0900UT. THE ACE SPACECRAFT ALSO
DETECTED AN INTERPLANETARY SHOCK PASSAGE AT L1 AT 12/0322UT FOLLOWED
BY A SUDDEN IMPULSE AT EARTH AT 12/0400UT (21 NT, AS MEASURED BY THE
BOULDER USGS MAGNETOMETER).

NO PROTON EVENTS WERE DETECTED AT GEO-SYNCHRONOUS ORBIT DURING THE
PERIOD.

THE GREATER THAN 2 MEV ELECTRON FLUX WAS AT MODERATE TO HIGH LEVELS
DURING MOST OF THE PERIOD.

THE GEOMAGNETIC FIELD WAS PREDOMINATELY QUIET TO ACTIVE WITH MINOR
STORM CONDITIONS OCCURRING ON 12 SEPTEMBER. THE UNSETTLED TO ACTIVE
CONDITIONS WERE CAUSED BY RECURRENT CORONAL HOLE EFFECTS. MINOR
STORM ACTIVITY ON 12 SEPTEMBER WAS MOST LIKELY CAUSED BY THE
INTERPLANETARY SHOCK AND CORRESPONDING SOUTHWARD IMF BZ DESCRIBED
ABOVE.

FORECAST OF SOLAR AND GEOMAGNETIC ACTIVITY
15 SEPTEMBER - 11 OCTOBER 1999

SOLAR ACTIVITY IS EXPECTED TO RANGE FROM LOW TO MODERATE LEVELS WITH
A SLIGHT CHANCE FOR MAJOR FLARES. AN INCREASING TREND IS EXPECTED TO
COMMENCE AROUND 16 SEPTEMBER WITH THE RETURN OF OLD REGION 8674
(S24, L=246), WHICH PRODUCED ISOLATED MAJOR FLARES DURING ITS LAST
ROTATION.

THERE WILL BE AN INCREASED CHANCE FOR A PROTON EVENT AT
GEO-SYNCHRONOUS ORBIT BEGINNING AROUND 16 SEPTEMBER.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEO-SYNCHRONOUS ALTITUDE IS
EXPECTED TO BE AT MODERATE TO HIGH LEVELS BEGINNING AROUND 13
SEPTEMBER

GEOMAGNETIC FIELD ACTIVITY IS EXPECTED VARY FROM QUIET TO UNSETTLED
LEVELS DURING MOST OF THE PERIOD. HOWEVER, ACTIVE PERIODS WILL BE
POSSIBLE AROUND 12 - 16 SEPTEMBER AND AGAIN AROUND 26 SEPTEMBER - 01
OCTOBER DUE TO RECURRENT HIGH SPEED SOLAR WIND STREAMS.

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