Viewing archive of Friday, 18 September 1998
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 1998 Sep 18 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 261 Issued at 2200Z on 18 SEP 1998IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z SOLAR ACTIVITY WAS VERY LOW. REGION 8339 (S16E30)
EXHIBITED SOME MINOR GROWTH AND PRODUCED SEVERAL SUBFLARES DURING
THE LATTER HALF OF THE PERIOD. NO SIGNIFICANT X-RAY ENHANCEMENTS
ACCOMPANIED THESE FLARES. REGION 8340 (N22E64) IS LIKELY THE MOST
COMPLEX REGION ON THE VISIBLE DISK BUT ITS LIMB PROXIMITY IS STILL
HAMPERING A DETAILED ANALYSIS. PERIODS OF SURGING WITH SEVERAL PLAGE
FLUCTUATIONS WERE NOTED IN THIS REGION AND A SMALL FILAMENT ERUPTED
LATE IN THE PERIOD. A PROMINENCE ERUPTED OFF THE SW LIMB AT
17/2250Z. THE REMAINING REGIONS WERE QUIET.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE VERY
LOW TO LOW. THOUGH NO FLARING HAS YET OCCURRED IN REGION 8340, ITS
SIZE AND APPARENT COMPLEXITY WILL LIKELY PRODUCE ISOLATED C-CLASS
FLARING.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
THE GEOMAGNETIC FIELD WAS QUIET UNTIL APPROXIMATELY 18/1100Z. A
DISTURBANCE BEGAN AT THAT TIME PRODUCING UNSETTLED TO ACTIVE
CONDITIONS WITH AN ISOLATED PERIOD OF MAJOR STORMING AT HIGH
LATITUDES. PREDOMINANTLY UNSETTLED TO ACTIVE CONDITIONS HAVE BEEN
OBSERVED AT ALL LATITUDES SINCE 18/1500Z.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN UNSETTLED TO ACTIVE. A LARGE EXTENSION OF THE
NORTHERN CORONAL HOLE WILL MOVE INTO FAVORABLE POSITION FOR
GEOEFFECTIVENESS BY LATE TOMORROW. DISTURBED CONDITIONS ARE
EXPECTED TO PERSIST THROUGH THE EARLY PART OF NEXT WEEK.
III. Event Probabilities 19 SEP to 21 SEP
| Class M | 10% | 15% | 15% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 18 SEP 123 Predicted 19 SEP-21 SEP 125/130/130 90 Day Mean 18 SEP 127
V. Geomagnetic A Indices
OBSERVED AFR/AP 17 SEP 005/007 ESTIMATED AFR/AP 18 SEP 017/010 PREDICTED AFR/AP 19 SEP-21 SEP 015/015-015/015-015/020
VI. Geomagnetic Activity Probabilities 19 SEP to 21 SEP
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 35% | 35% | 35% |
| Minor storm | 10% | 10% | 10% |
| Major-severe storm | 05% | 05% | 05% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 45% | 45% | 45% |
| Minor storm | 20% | 25% | 25% |
| Major-severe storm | 05% | 10% | 10% |
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