Viewing archive of Saturday, 17 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 17 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 107 Issued at 2200Z on 17 APR 1999IA. Analysis of Solar Active Regions and Activity from 16-2100Z to 17-2100Z SOLAR ACTIVITY WAS VERY LOW. TWO NEW REGIONS WERE
ASSIGNED TODAY: REGION 8518 NEAR S16E66 AND REGION 8519 NEAR N17W33.
TWO FILAMENTS ERUPTED DURING THE PERIOD: AN 8 DEGREE FILAMENT NEAR
S19W08 BETWEEN 16/2144UT AND 17/1116UT AND A 20 DEGREE FILAMENT NEAR
S32W15 BETWEEN 17/1640-1830UT.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW
FOR THE NEXT THREE DAYS.
IIA. Geophysical Activity Summary 16-2100Z to 17-2100Z
THE GEOMAGNETIC FIELD RANGED FROM UNSETTLED TO MAJOR STORM LEVELS. A
GEOMAGNETIC DISTURBANCE THAT BEGAN WITH A SUDDEN IMPULSE YESTERDAY
AT 16/1126Z INTENSIFIED INTO A GEOMAGNETIC STORM. MID-LATITUDES WERE
AT MINOR TO MAJOR STORM LEVELS ON THE 17TH FROM 00-09UT AND HIGH
LATITUDES WERE AT MAJOR TO SEVERE STORM LEVELS DURING THE SAME TIME
INTERVAL. THE DISTURBANCE SUBSIDED AFTER 0900Z WITH PREDOMINANTLY
UNSETTLED CONDITIONS PREVAILING FROM 1200 TO THE END OF THE DAY.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO BE MOSTLY UNSETTLED FOR THE NEXT 24 HOURS, AND IS
EXPECTED TO BE QUIET TO UNSETTLED FOR THE SECOND AND THIRD DAYS.
III. Event Probabilities 18 APR to 20 APR
| Class M | 15% | 15% | 15% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 17 APR 116 Predicted 18 APR-20 APR 114/112/110 90 Day Mean 17 APR 134
V. Geomagnetic A Indices
OBSERVED AFR/AP 16 APR 013/014 ESTIMATED AFR/AP 17 APR 035/045 PREDICTED AFR/AP 18 APR-20 APR 010/010-005/010-010/012
VI. Geomagnetic Activity Probabilities 18 APR to 20 APR
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 20% | 15% | 15% |
| Minor storm | 10% | 10% | 10% |
| Major-severe storm | 05% | 01% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 35% | 25% | 20% |
| Minor storm | 15% | 10% | 10% |
| Major-severe storm | 10% | 05% | 05% |
All times in UTC
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