Viewing archive of Thursday, 27 August 1998

Solar activity report

Report of Solar-Geophysical Activity 1998 Aug 27 2200 UTC
Prepared by the NOAA © SWPC and processed by SpaceWeatherLive.com

Joint USAF/NOAA Report of Solar and Geophysical Activity

::::::::::CORRECTED COPY ::::::::::::::: 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 FROM 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 M25%25%25%
Class X10%10%10%
Proton25%25%25%
PCAFGREEN
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
Active30%40%40%
Minor storm30%10%10%
Major-severe storm20%05%05%
B. High Latitudes
Active30%40%40%
Minor storm40%10%10%
Major-severe storm15%05%05%

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