Viewing archive of Thursday, 21 October 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 Oct 21 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 294 Issued at 2200Z on 21 OCT 1999IA. Analysis of Solar Active Regions and Activity from 20-2100Z to 21-2100Z SOLAR ACTIVITY WAS LOW. THERE WERE SEVERAL C-CLASS
SUBFLARES DURING THE DAY. MOST OF THESE WERE FROM REGIONS 8732
(N21W76) AND 8739 (S12E58). REGIONS 8739 AND 8737 (S15W12) BOTH
SHOWED GROWTH DURING THE PAST 24 HOURS. REGION 8731 (N12W68)
CONTINUES TO BE THE LARGEST REGION ON THE DISK BUT WAS RELATIVELY
QUIET AND STABLE.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. REGIONS 8731 AND 8732 CONTINUE TO BE THE MOST LIKELY
SOURCES FOR ENERGETIC FLARES.
IIA. Geophysical Activity Summary 20-2100Z to 21-2100Z
THE GEOMAGNETIC FIELD WAS QUIET TO ACTIVE. A SUDDEN IMPULSE WAS
OBSERVED AT 0226Z, WHICH WAS PRECEDED BY A SHOCK OBSERVED AT THE ACE
SPACECRAFT AT 0138Z. THE SHOCK WAS FOLLOWED BY AN INTERPLANETARY
TRANSIENT, BUT THE TRANSIENT WAS NOT VERY GEOEFFECTIVE: ONLY ONE
ACTIVE PERIOD OCCURRED FROM 0300-0600Z. THE REMAINDER OF THE DAY WAS
QUIET TO UNSETTLED. THE GREATER THAN 2 MEV ELECTRON FLUXES EXCEEDED
HIGH LEVELS.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO BE UNSETTLED TO ACTIVE FOR THE NEXT 24 HOURS. THERE IS A
GOOD CHANCE FOR SOME ENHANCED ACTIVITY DURING LOCAL NIGHTTIME HOURS.
CONDITIONS SHOULD SUBSIDE A BIT ON THE SECOND DAY, BUT ANOTHER
INCREASE IS ANTICIPATED ON THE THIRD DAY IN RESPONSE TO A FAVORABLY
POSITIONED CORONAL HOLE.
III. Event Probabilities 22 OCT to 24 OCT
| Class M | 40% | 35% | 30% |
| Class X | 10% | 05% | 05% |
| Proton | 10% | 05% | 05% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 21 OCT 159 Predicted 22 OCT-24 OCT 150/145/140 90 Day Mean 21 OCT 158
V. Geomagnetic A Indices
OBSERVED AFR/AP 20 OCT 004/004 ESTIMATED AFR/AP 21 OCT 012/012 PREDICTED AFR/AP 22 OCT-24 OCT 015/020-015/010-020/015
VI. Geomagnetic Activity Probabilities 22 OCT to 24 OCT
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 40% | 40% | 50% |
| Minor storm | 20% | 20% | 30% |
| Major-severe storm | 05% | 05% | 10% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 50% | 50% | 40% |
| Minor storm | 25% | 25% | 35% |
| Major-severe storm | 15% | 15% | 20% |
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