Viewing archive of Thursday, 19 April 2001

Solar activity report

Report of Solar-Geophysical Activity 2001 Apr 19 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 109 Issued at 2200Z on 19 Apr 2001

IA. Analysis of Solar Active Regions and Activity from 18-2100Z to 19-2100Z

Solar activity was moderate due to an M2 x-ray flare at 19/1135 UTC. An optical flare report was not received but SOHO/EIT difference images suggest the source was Region 9433 (N17E64), the return of old 9393. All of this region appears to have rotated onto the disk and is presently seen as a moderately-sized (700 millionths) F-type sunspot group with some mixed polarities. This area also produced a few small C-class subflares during the day. Interestingly, a CME was visible entering the SOHO/LASCO/C2 field of view over the northwest limb shortly after the M2 at about 19/1200 UTC. The location suggests that departed Region 9415 was involved with this activity but any connection to the M2 discussed above may only be coincidental. Regions 9434 (N19W23) and 9435 (S21E28) were numbered.
IB. Solar Activity Forecast
Solar activity is expected to be low to moderate. Region 9433 is expected to continue to produce C-class flares and appears capable of additional M-class activity.
IIA. Geophysical Activity Summary 18-2100Z to 19-2100Z
The geomagnetic field has been quiet to unsettled. The greater than 100 MeV proton event ended at 19/0325 UTC (start 18/0315 UTC, 12 pfu peak at 18/0600 UTC). The polar cap absorption (PCA) event has also ended (19/1400 UTC). The greater than 10 MeV proton event continues in progress (start 18/0315 UTC, 321 pfu peak at 18/1045 UTC, and current flux about 15 pfu at 19/2100 UTC) and is slowly decaying.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to continue at quiet to unsettled levels. The greater than 10 MeV proton event is expected to drop below event threshold sometime tomorrow (April 20 UTC).
III. Event Probabilities 20 Apr to 22 Apr
Class M50%50%50%
Class X05%05%05%
IV. Penticton 10.7 cm Flux
  Observed       19 Apr 145
  Predicted   20 Apr-22 Apr  155/165/175
  90 Day Mean        19 Apr 165
V. Geomagnetic A Indices
  Observed Afr/Ap 18 Apr  022/050
  Estimated     Afr/Ap 19 Apr  010/008
  Predicted    Afr/Ap 20 Apr-22 Apr  010/010-010/010-010/010
VI. Geomagnetic Activity Probabilities 20 Apr to 22 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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