Viewing archive of Thursday, 27 August 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 Aug 27 2200 UTC
Prepared by the NOAA © SWPC and processed by SpaceWeatherLive.comJoint USAF/NOAA Report of Solar and Geophysical Activity
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SDF Number 239 Issued at 2200Z on 27 AUG 1998
IA. Analysis of Solar Active Regions and Activity from 26-2100Z to 27-2100Z
SOLAR ACTIVITY HAS BEEN LOW. THE ONLY ACTIVITY
HAS BEEN A C-CLASS X-RAY BURSTS AND SUBFLARES FROM REGIONS 8307
(N31W28) AND 8319 (N21W03). REGION 8307 CONTINUES ITS SLOW DECAY
AND SIMPLIFICATION. FILAMENT ACTIVITY WITHIN THE REGION HAS
DECREASED. REGION 8319 (N19W03) HAS CONTINUED TO GROW AND DEVELOP.
IT IS STILL SIMPLE AND SMALL IN SPOT AREA, BUT THE PLAGE AREA HAS
GROWN. SUBFLARES AND ARCH FILAMENT SYSTEMS INDICATE THE REGION IS
STILL EMERGING. THE REGION IS CLOSE TO OLDER REGION 8314 (N16E03)
AND IF DEVELOPMENT CONTINUES IN 8319, THE MERGER OF THE REGIONS MAY
PRODUCE ACTIVITY AS A RESULT OF THEIR INTERACTION.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE
LOW TO MODERATE. A SPORADIC CLASS M FLARE IS POSSIBLE FROM REGION
8307. THE DEVELOPING COMPLEX OF REGIONS 8314/8319 IS LIKELY TO
PRODUCE FREQUENT SMALL FLARES WITH A LIKELIHOOD OF STRONGER ACTIVITY
OVER THE NEXT SEVERAL DAYS.
IIA. Geophysical Activity Summary 26-2100Z to 27-2100Z
THE GEOMAGNETIC FIELD HAS BEEN AT UNSETTLED TO SEVERE STORM LEVELS.
MID-LATITUDE K-INDICES REACHED 7 AND 8 BETWEEN 27/0300 UT AND
27/1200 UT. THE FORBUSH DECREASE THAT BEGAN LATE ON 25 AUGUST
CONTINUES, WITH NEUTRON MONITOR COUNTING RATES FROM THULE DEPRESSED
BY ABOUT 6 PERCENT TODAY. ACE REAL-TIME SOLAR WIND DATA HAS
PROVIDED CONTINUOUS INFORMATION THROUGH THE PERIOD OF THE
GEOMAGNETIC STORM. FROM 26/0600 UT THROUGH 26/2200 UT, THE
ESTIMATED SOLAR WIND VELOCITY INCREASED STEADILY FROM ABOUT 400 KM/S
TO APPROXIMATELY 900 KM/S, THEN DECLINED JUST AS STEADILY TO ABOUT
600 KM/S BY 27/0900 UT. AT THE SAME TIME, THE DENSITY REMAINED LESS
THAN 10 /CM3 AND THE TEMPERATURE INCREASED FROM 500,000 K UP TO
1,000,000 K AT 26/2100 UT, THEN DOWN TO 20,000 AT 27/1300 UT. THE
RESULT APPEARED TO BE A FAST, HOT, LOW-DENSITY STREAM. THE
INTERPLANETARY BZ FIELD HAS REMAINED NEARLY FLAT AT ABOUT -10 TO -15
NANOTESLA MOST OF TODAY, BUT HAS SHOWN SIGNS OF MOVING TOWARD LESS
NEGATIVE VALUES OVER THE PAST 6 HOURS. THE GREATER THAN 10 MEV
PROTON FLUXES HAVE REMAINED ABOVE EVENT THRESHOLDS THROUGHOUT 27
AUGUST. THE GREATER THAN 100 MEV PROTON EVENT WAS DECLARED OVER AT
26/2050 UT. ENERGETIC ELECTRONS FLUXES GREATER THAN 2 MEV, AS
MEASURED BY THE GOES SATELLITE AT GEOSYNCHRONOUS ORBIT, HAD
DECREASED TO ABOUT 10 PFU EARLY ON 27 AUG AFTER PREVIOUSLY REACHING
NEAR THE SEC ALERT THRESHOLD OF 1000 PFU ON PREVIOUS DAYS. SINCE
27/0900 UT, THE FLUXES HAVE BEEN INCREASING.
IIB. Geophysical Activity Forecast
GEOMAGNETIC ACTIVITY IS
EXPECTED TO CONTINUE AT MINOR TO MAJOR STORM LEVELS BUT WITH
DECLINING INTENSITY OVER THE NEXT 24 HOURS, REACHING ACTIVE TO MINOR
STORM LEVELS BY THE END OF THE DAY TOMORROW. MID-LATITUDE K-INDICES
ARE MOST LIKELY TO REACH VALUES OF 6 OR 7 DURING THE COMING WESTERN
HEMISPHERE NIGHT TIME. ENERGETIC ELECTRON FLUXES GREATER THAN 2 MEV
WILL REACH ALERT LEVELS BY THE TIME THIS FORECAST IS EFFECTIVE. THE GREATER
THAN 10 MEV PROTON FLUXES ARE LIKELY TO CONTINUE THEIR SLOW DECLINE
BUT REMAIN ABOVE EVENT THRESHOLDS WELL INTO 27 AUGUST. THE CURRENT
FORBUSH DECREASE IS EXPECT TO CONTINUE TO DECLINE IN INTENSITY.
III. Event Probabilities 28 AUG to 30 AUG
Class M | 25% | 25% | 25% |
Class X | 10% | 10% | 10% |
Proton | 25% | 25% | 25% |
PCAF | GREEN
|
IV. Penticton 10.7 cm Flux
Observed 27 AUG 135
Predicted 28 AUG-30 AUG 135/135/135
90 Day Mean 27 AUG 117
V. Geomagnetic A Indices
OBSERVED AFR/AP 26 AUG 028/039
ESTIMATED AFR/AP 27 AUG 084/107
PREDICTED AFR/AP 28 AUG-30 AUG 030/030-010/015-010/010
VI. Geomagnetic Activity Probabilities 28 AUG to 30 AUG
A. Middle Latitudes |
Active | 30% | 40% | 40% |
Minor storm | 30% | 10% | 10% |
Major-severe storm | 20% | 05% | 05% |
B. High Latitudes |
Active | 30% | 40% | 40% |
Minor storm | 40% | 10% | 10% |
Major-severe storm | 15% | 05% | 05% |
All times in UTC
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