Viewing archive of Tuesday, 20 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 20 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 110 Issued at 2200Z on 20 APR 1999IA. Analysis of Solar Active Regions and Activity from 19-2100Z to 20-2100Z SOLAR ACTIVITY REMAINED AT VERY LOW LEVELS. REGIONS
8517 (N22W77) AND 8518 (S15E29) PRODUCED ISOLATED B-CLASS SUBFLARES,
BUT SHOWED NO SIGNIFICANT CHANGES IN SIZE OR STRUCTURE. THE
REMAINING SPOT GROUPS WERE SMALL, STRUCTURALLY SIMPLE, AND STABLE.
NO NEW REGIONS WERE ASSIGNED.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE VERY
LOW TO LOW. REGION 8518 APPEARS CAPABLE OF ISOLATED C-CLASS FLARE
PRODUCTION.
IIA. Geophysical Activity Summary 19-2100Z to 20-2100Z
THE GEOMAGNETIC FIELD WAS AT UNSETTLED TO MINOR STORM LEVELS AT ALL
LATITUDES.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN AT UNSETTLED TO MINOR STORM LEVELS DURING THE
FIRST DAY, THEN DECLINE TO QUIET TO UNSETTLED LEVELS FOR THE
REMAINDER OF THE PERIOD.
III. Event Probabilities 21 APR to 23 APR
| Class M | 10% | 10% | 10% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 20 APR 105 Predicted 21 APR-23 APR 105/105/105 90 Day Mean 20 APR 132
V. Geomagnetic A Indices
OBSERVED AFR/AP 19 APR 010/013 ESTIMATED AFR/AP 20 APR 022/022 PREDICTED AFR/AP 21 APR-23 APR 020/030-010/010-007/005
VI. Geomagnetic Activity Probabilities 21 APR to 23 APR
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 40% | 20% | 10% |
| Minor storm | 30% | 10% | 05% |
| Major-severe storm | 05% | 01% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 40% | 25% | 10% |
| Minor storm | 40% | 15% | 10% |
| Major-severe storm | 05% | 01% | 01% |
All times in UTC
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