Viewing archive of Friday, 17 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 17 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 260 Issued at 2200Z on 17 SEP 1999IA. Analysis of Solar Active Regions and Activity from 16-2100Z to 17-2100Z SOLAR ACTIVITY INCREASED TO MODERATE LEVELS. REGION
8690 (N16W74) SHOWED GRADUAL DECAY AS IT APPROACHED THE WEST LIMB.
IT PRODUCED AN M2/SF AT 17/0120Z. REGION 8700 (N13E20) SHOWED SOME
MIXED POLARITIES AS IT GRADUALLY DECAYED AND PRODUCED ISOLATED
C-CLASS SUBFLARES. A PARTIAL-HALO CME WAS OBSERVED FOLLOWING
YESTERDAY'S (16/1508 - 1615Z) 50-DEGREE DSF. NEW REGIONS 8702
(N22E15), 8703 (N21W92), AND 8704 (S21E63) WERE NUMBERED. REGION
8704 APPEARED TO BE THE RETURN OF OLD REGION 8674, WHICH PRODUCED
MAJOR FLARES DURING ITS PREVIOUS ROTATIONS. THUS FAR, IT HAS BEEN A
STABLE H-TYPE GROUP.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW
WITH A SLIGHT CHANCE FOR AN M-CLASS FLARE FROM REGIONS 8690 AND
8700.
IIA. Geophysical Activity Summary 16-2100Z to 17-2100Z
THE GEOMAGNETIC FIELD WAS AT QUIET TO ACTIVE LEVELS WITH PERIODS OF
MINOR TO MAJOR STORMING DETECTED AT HIGH LATITUDES. THE GREATER THAN
2 MEV ELECTRON FLUX REACHED HIGH LEVELS DURING THE PERIOD.
IIB. Geophysical Activity Forecast
GEOMAGNETIC FIELD ACTIVITY IS
EXPECTED TO BE AT MOSTLY QUIET TO UNSETTLED LEVELS DURING THE FIRST
DAY. ACTIVITY IS EXPECTED TO INCREASE TO ACTIVE TO MINOR STORM
LEVELS LATE ON 19 SEPTEMBER DUE TO YESTERDAY'S DSF/CME. STORM LEVELS
ARE EXPECTED TO CONTINUE THROUGH THE END OF THE PERIOD. THE GREATER
THAN 2 MEV ELECTRON FLUX IS EXPECTED TO BE AT MODERATE TO HIGH
LEVELS DURING THE PERIOD.
III. Event Probabilities 18 SEP to 20 SEP
| Class M | 15% | 15% | 15% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 17 SEP 158 Predicted 18 SEP-20 SEP 160/165/170 90 Day Mean 17 SEP 164
V. Geomagnetic A Indices
OBSERVED AFR/AP 16 SEP 018/032 ESTIMATED AFR/AP 17 SEP 012/020 PREDICTED AFR/AP 18 SEP-20 SEP 015/015-015/015-030/030
VI. Geomagnetic Activity Probabilities 18 SEP to 20 SEP
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 30% | 50% | 50% |
| Minor storm | 10% | 30% | 30% |
| Major-severe storm | 05% | 10% | 10% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 40% | 50% | 50% |
| Minor storm | 15% | 30% | 30% |
| Major-severe storm | 05% | 10% | 10% |
All times in UTC
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