Viewing archive of Thursday, 18 February 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 Feb 18 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 049 Issued at 2200Z on 18 FEB 1999IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z SOLAR ACTIVITY WAS LOW. THE DAY'S LARGEST EVENT WAS A
C5 XRAY BURST AT 0329Z. THERE WAS NO ASSOCIATED OPTICAL FLARE.
REGION 8462 (N20W40) PRODUCED MOST OF THE C-CLASS EVENTS OBSERVED,
AND REGIONS 8458 (S23W36) AND 8459 (S29W80) SPLIT THE REMAINDER. IN
GENERAL, ALL SPOTTED REGIONS WERE STABLE OR DECAYING AND THE 10.7 CM
RADIO FLUX DROPPED SUBSTANTIALLY FROM YESTERDAY. THE LIMBS WERE
QUIET.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW
TO MODERATE. REGIONS 8458 AND 8462 ARE POTENTIAL SITES FOR M-CLASS
ACTIVITY, SHOULD AN INSTABILITY DEVELOP.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
THE GEOMAGNETIC FIELD WAS AT ACTIVE TO SEVERE STORM LEVELS THROUGHOUT
THE PERIOD. A SUDDEN STORM COMMENCEMENT MEASURING 43 NANOTESLAS AT
BOULDER, OCCURRED AT 0250Z. THE ACE SPACECRAFT MEASURED SOLAR WIND
VELOCITIES NEAR 700 KM/S, AND SOUTHWARD IMF OF APPROXIMATELY 20 NT,
FOR HOURS FOLLOWING THE PASSAGE OF THE SHOCK. THE SOLAR ORIGIN OF
THIS ACTIVITY IS THOUGHT TO BE THE LONG-DURATION M-CLASS EVENT FROM
NEAR CENTER DISK, EARLY ON FEBRUARY 16. A FORBUSH DECREASE BEGAN
EARLY IN THE DAY, AS SEEN IN NEUTRON MONITOR DATA.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO BE AT ACTIVE TO MINOR STORM LEVELS FOR THE NEXT 24
HOURS. THE CURRENT STORM SHOULD GRADUALLY WEAKEN, ALTHOUGH EPISODES
OF MAJOR STORM MAY OCCUR DURING LOCAL NIGHTTIMES. THE SOLAR WIND
SPEED AT ACE IS STILL ABOVE 600 KM/S, BUT THE SOUTHWARD COMPONENT OF
THE IMF IS NOW NEAR ZERO. THE RETURN TO MORE BENIGN CONDITIONS
SHOULD BRING QUIET TO UNSETTLED LEVELS BY FEBRUARY 21.
III. Event Probabilities 19 FEB to 21 FEB
| Class M | 50% | 50% | 50% |
| Class X | 05% | 05% | 05% |
| Proton | 05% | 05% | 05% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 18 FEB 168 Predicted 19 FEB-21 FEB 160/155/150 90 Day Mean 18 FEB 146
V. Geomagnetic A Indices
OBSERVED AFR/AP 17 FEB 015/016 ESTIMATED AFR/AP 18 FEB 060/050 PREDICTED AFR/AP 19 FEB-21 FEB 030/030-015/015-005/010
VI. Geomagnetic Activity Probabilities 19 FEB to 21 FEB
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 10% | 40% | 10% |
| Minor storm | 60% | 20% | 05% |
| Major-severe storm | 25% | 05% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 10% | 50% | 20% |
| Minor storm | 60% | 30% | 10% |
| Major-severe storm | 30% | 10% | 01% |
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