Viewing archive of Friday, 20 April 2001

Solar activity report

Report of Solar-Geophysical Activity 2001 Apr 20 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 110 Issued at 2200Z on 20 Apr 2001

IA. Analysis of Solar Active Regions and Activity from 19-2100Z to 20-2100Z

Solar activity was moderate. The largest flare was an M4/1F at 20/2004 UTC in Region 9433 (N17E52). This area also produced an M1/1F at 20/0523 UTC. The region remains a moderately-sized F-type sunspot group with some mixed polarities in the central portions and a total area similar to yesterday's. Region 9432 (N08W06) also produced C-class subflares. Today's Penticton F10.7 noon reading was taken during the M4, resulting in a flare-enhanced value of 180 sfu.
IB. Solar Activity Forecast
Solar activity is expected to be moderate. Additional M-class activity in Region 9433 is likely with the possibility of an isolated major flare.
IIA. Geophysical Activity Summary 19-2100Z to 20-2100Z
The geomagnetic field was quiet to unsettled. The greater than 10 MeV proton event dropped below the 10 pfu event threshold at 20/1015 UTC (start 18/0315 UTC and 321 pfu peak at 18/1045 UTC) and continues to slowly decay.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be quiet to unsettled. A major flare in Region 9433 could generate another greater than 10 MeV proton event.
III. Event Probabilities 21 Apr to 23 Apr
Class M75%75%75%
Class X10%10%10%
IV. Penticton 10.7 cm Flux
  Observed       20 Apr 180
  Predicted   21 Apr-23 Apr  175/185/195
  90 Day Mean        20 Apr 165
V. Geomagnetic A Indices
  Observed Afr/Ap 19 Apr  005/007
  Estimated     Afr/Ap 20 Apr  008/010
  Predicted    Afr/Ap 21 Apr-23 Apr  005/010-005/010-010/010
VI. Geomagnetic Activity Probabilities 21 Apr to 23 Apr
A. Middle Latitudes
Minor storm05%05%05%
Major-severe storm01%01%01%
B. High Latitudes
Minor storm10%10%10%
Major-severe storm01%01%01%

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