Viewing archive of Sunday, 18 April 1999
Solar activity report
Any mentioned solar flare in this report has a scaling factor applied by the Space Weather Prediction Center (SWPC). Because of the SWPC scaling factor, solar flares are reported as 42% smaller than for the science quality data. The scaling factor has been removed from our archived solar flare data to reflect the true physical units.
Report of Solar-Geophysical Activity 1999 Apr 18 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 108 Issued at 2200Z on 18 APR 1999IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z SOLAR ACTIVITY REMAINED AT VERY LOW LEVELS. ISOLATED
B-CLASS X-RAY FLARES OCCURRED, TWO OF WHICH WERE OPTICALLY TIED TO
REGION 8514 (S33W69). THIS REGION SHOWED GRADUAL DECAY AS IT
APPROACHED THE WEST LIMB. ALL THE REMAINING REGIONS WERE EITHER
STABLE OR DECLINING SLOWLY. A 21-DEGREE FILAMENT, LAST SEEN CENTERED
NEAR N19E03, DISAPPEARED EARLY IN THE PERIOD. A PARTIAL-HALO CME WAS
OBSERVED AROUND 17/0600Z. NO NEW REGIONS WERE ASSIGNED.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO REMAIN
AT VERY LOW LEVELS.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
THE GEOMAGNETIC FIELD WAS MOSTLY QUIET WITH BRIEF UNSETTLED INTERVALS
AT ALL LATITUDES.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO BE AT QUIET TO UNSETTLED LEVELS DURING THE FIRST TWO
DAYS, THEN INCREASE TO ACTIVE LEVELS ON THE THIRD DAY IN RESPONSE TO
THE CME MENTIONED ABOVE.
III. Event Probabilities 19 APR to 21 APR
| Class M | 10% | 10% | 10% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 18 APR 113 Predicted 19 APR-21 APR 110/110/110 90 Day Mean 18 APR 134
V. Geomagnetic A Indices
OBSERVED AFR/AP 17 APR 030/047 ESTIMATED AFR/AP 18 APR 008/010 PREDICTED AFR/AP 19 APR-21 APR 005/008-010/012-020/015
VI. Geomagnetic Activity Probabilities 19 APR to 21 APR
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 10% | 15% | 50% |
| Minor storm | 05% | 05% | 10% |
| Major-severe storm | 01% | 01% | 05% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 15% | 20% | 50% |
| Minor storm | 10% | 10% | 20% |
| Major-severe storm | 01% | 01% | 05% |
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