:Product: Weekly Highlights and Forecasts
:Issued: 2000 Apr 11 2112 UT
HIGHLIGHTS OF SOLAR AND GEOMAGNETIC ACTIVITY
03 - 09 APRIL 2000

SOLAR ACTIVITY RANGED FROM LOW TO MODERATE LEVELS. THE PERIOD BEGAN
WITH ACTIVITY AT LOW LEVELS ON 03 APRIL. REGION 8948 (S15, L = 130,
CLASS/AREA EAI/160 ON 09 APRIL) PRODUCED ISOLATED M-CLASS FLARES
WHICH INCLUDED AN OPTICALLY UNCORRELATED M1 FLARE ON 04 APRIL. THE
LOCATION WAS VERIFIED BY USING EIT IMAGES FROM THE SOHO SPACECRAFT.
REGION 8933 (N17, L = 267, CLASS/AREA EKO/420 ON 04 APRIL) PRODUCED
A C9/2F EVENT ON 04/1541UT. THIS EVENT WAS ACCOMPANIED BY A
DISAPPEARING SOLAR FILAMENT (DSF) AND A CORONAL MASS EJECTION (CME)
THAT PRODUCED GEOMAGNETIC STORMING LATER IN THE PERIOD. SOLAR
ACTIVITY WAS LOW ON 05 APRIL AND MODERATE ON 06 APRIL DUE TO AN
M1/2B EVENT AT 06/0229UT FROM REGION 8948. ACTIVITY WAS LOW ON 07
APRIL AND MODERATE FOR THE LAST TWO DAYS OF THE PERIOD. REGION 8948
PRODUCED ISOLATED M-CLASS EVENTS DURING THAT TIME, AN M2/1B ON
08/0240UT, AN M1/1N ON 08/2046UT AND AN M1/1N ON 09/0416UT. REGION
8948 WAS BY FAR THE MOST ACTIVE REGION DURING THE PERIOD, BECOMING
52-SPOT EAI GROUP WITH A GAMMA-DELTA MAGNETIC CLASSIFICATION ON 09
APRIL.

REAL-TIME SOLAR WIND DATA WERE AVAILABLE FROM THE NASA ADVANCED
COMPOSITION EXPLORER (ACE) SPACECRAFT FOR MOST OF THE PERIOD.
CHANGES IN THE INTERPLANETARY FIELD WERE OBSERVED ON 04 APRIL. IMF
BZ BEGAN THE DAY AROUND -7 NT, TURNED POSITIVE (+10 NT) AROUND
04/0200UT, AND RETURNED NEGATIVE (-7 NT) AFTER 04/1100UT. A SHOCK
WAS DETECTED AT 06/1600UT, AT THAT TIME VELOCITY JUMPED FROM 400
KM/S TO 560 TO 580 KM/S. AN ASSOCIATED SUDDEN IMPULSE WAS DETECTED
AT 06/1640 OF 37 NT, AS OBSERVED AT SAN JUAN. THIS DISTURBANCE WAS
MOST LIKELY THE CONSEQUENCE OF THE HALO CME ASSOCIATED WITH THE
C9/2F FLARE ON 04 APRIL. SOLAR WIND SPEEDS REMAINED ELEVATED FOR THE
REMAINDER OF THE PERIOD, RANGING FROM 510 TO 620 KM/S ON 09 APRIL.

THE GREATER THAN 10 MEV PROTONS AT GEOSYNCHRONOUS ORBIT REACHED THE
10 PFU LEVEL AT 04/2055UT. THE GREATER THAN 10 MEV PROTONS PEAKED AT
55 PFU ON 05/0653UT AND THE PROTON EVENT ENDED AT 06/0155UT. AN
ASSOCIATED POLAR CAP ABSORPTION (PCA) EVENT BEGAN AT 05/0653UT,
REACHED A MAXIMUM OF 2.2 DB AT 05/0950UT, AND ENDED AT 05/1807UT.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT WAS AT
NORMAL TO MODERATE LEVELS.

THE GEOMAGNETIC FIELD BEGAN THE PERIOD AT QUIET TO UNSETTLED LEVELS.
MAJOR STORMING WAS OBSERVED ON 04 APRIL DUE TO IMF BZ FLUCTUATIONS
DESCRIBED ABOVE. UNSETTLED TO ACTIVE CONDITIONS WERE OBSERVED ON 05
APRIL. MAJOR STORMS OCCURRED ON 06 APRIL AND SEVERE STORMS OCCURRED
ON 07 APRIL DUE TO THE HALO CME OBSERVED ON 04 APRIL. CONDITIONS
WERE MOSTLY QUIET TO UNSETTLED FOR THE REMAINDER OF THE PERIOD WITH
ISOLATED ACTIVE CONDITIONS REPORTED AT HIGH LATITUDES ON 08 APRIL.

FORECAST OF SOLAR AND GEOMAGNETIC ACTIVITY
12 APRIL - 08 MAY 2000

SOLAR ACTIVITY IS EXPECTED TO VARY BETWEEN LOW AND MODERATE LEVELS
WITH ISOLATED LOW-LEVEL M-CLASS FLARES LIKELY. THERE WILL ALSO BE A
SLIGHT CHANCE FOR ISOLATED MAJOR FLARE ACTIVITY SOMETIME DURING THE
PERIOD DUE TO THE RETURN OF PREVIOUSLY ACTIVE LONGITUDES.

THERE WILL BE A SLIGHT CHANCE FOR A PROTON FLUX EVENT AT
GEOSYNCHRONOUS ORBIT SOMETIME DURING THE PERIOD.

THE GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS
EXPECTED TO BE AT NORMAL TO MODERATE LEVELS DURING MOST OF THE
PERIOD.

BARRING AN EARTH-DIRECTED CORONAL MASS EJECTION (CME), GEOMAGNETIC
FIELD ACTIVITY IS EXPECTED TO BE AT QUIET TO UNSETTLED LEVELS FOR
MOST OF THE PERIOD.

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