Viewing archive of Saturday, 18 September 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 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 1999IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z
SOLAR ACTIVITY WAS LOW. REGION 8700 (N13E07) PRODUCED
THE LARGEST FLARE SINCE YESTERDAY, A C8/2F AT 17/2212UT. SEVERAL
SUBFLARES AND FLARE-BRIGHT PLAGE FLUCTUATIONS ALSO OCCURRED IN THIS
REGION. 8700 SUNSPOTS CONTINUE TO EXHIBIT MIXED POLARITIES. REGION
8699 (N22W65) ALSO PRODUCED C-CLASS ACTIVITY, THE LARGEST BEING A
C2/SF AT 18/1821UT. NEW REGION 8705 (S11E28) EMERGED ON THE DISK.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. C-CLASS ACTIVITY IS EXPECTED IN REGIONS 8699 AND 8700.
AN ISOLATED M-CLASS FLARE IS POSSIBLE IN REGION 8700.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
THE GEOMAGNETIC FIELD RANGED FROM QUIET TO ACTIVE. ACTIVITY LEVELS
CONTINUED TO FLUCTUATE IN RESPONSE TO SIMILAR SOLAR WIND (HIGH SPEED
AND VARIABLE BZ) EXPERIENCED FOR THE PAST FEW DAYS. THE GREATER THAN
2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT WAS HIGH.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN QUIET TO UNSETTLED FOR THE NEXT SEVERAL HOURS.
ACTIVE TO STORM CONDITIONS ARE POSSIBLE LATE ON THE 19TH, CONTINUING
THROUGH THE 20TH, DUE TO THE CME/DSF DETECTED ON THE 16TH. THE
GREATER THAN 2 MEV ELECTRON FLUX SHOULD REMAIN MODERATE TO HIGH.
III. Event Probabilities 19 SEP to 21 SEP
| Class M | 15% | 15% | 15% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 18 SEP 152 Predicted 19 SEP-21 SEP 155/160/165 90 Day Mean 18 SEP 164
V. Geomagnetic A Indices
OBSERVED AFR/AP 17 SEP 009/015 ESTIMATED AFR/AP 18 SEP 015/015 PREDICTED AFR/AP 19 SEP-21 SEP 015/015-030/030-015/015
VI. Geomagnetic Activity Probabilities 19 SEP to 21 SEP
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 50% | 50% | 30% |
| Minor storm | 20% | 30% | 10% |
| Major-severe storm | 05% | 10% | 05% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 50% | 50% | 30% |
| Minor storm | 20% | 30% | 10% |
| Major-severe storm | 05% | 10% | 05% |
All times in UTC
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