Viewing archive of Sunday, 21 April 2002

Solar activity report

Report of Solar-Geophysical Activity 2002 Apr 21 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 111 Issued at 2200Z on 21 Apr 2002

IA. Analysis of Solar Active Regions and Activity from 20-2100Z to 21-2100Z

Solar activity has been high. Region 9906 (S14W90) produced a long-duration X1/1f flare at 0151 UTC which was accompanied by strong radio bursts, type II and type IV radio sweeps, and a partial halo CME. The CME moved extremely rapidly in the plane of the sky with a projected velocity of 2400-2500 km/s. The front of the CME appeared to be moving away from the west limb and therefore approximately perpendicular to the line of sight. The remainder of today's activity consisted of a few C-class events. A filament was observed to lift off the northeast part of the disk at 21/0012 UTC and was associated with a narrow CME from the northeast limb. Region 9912 (N10W12) has continued to grow and is currently the largest group on the disk now that 9906 has rotated behind west limb. 9912 was stable and quiet. Two new regions were assigned today: 9915 (N11E54) and 9916 (S17E71).
IB. Solar Activity Forecast
Solar activity is expected to be low to moderate. Region 9906 could contribute an M-class event during the next 24 hours, but will become less of a threat as it moves further behind the limb. There is a slight chance for an isolated M-class event from Region 9912.
IIA. Geophysical Activity Summary 20-2100Z to 21-2100Z
The geomagnetic field was quiet to unsettled during the past 24 hours. A greater than 100 MeV proton event began at 21/0155 UTC in response to the X1 flare and continues in progress. The maximum flux observed so far was 23 PFU at 21/1025 UTC. A greater than 10 MeV proton event began at 21/0225 UTC and also continues in progress. The maximum flux at greater than 10 MeV was 2210 PFU at 21/1315 UTC.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be quiet to unsettled for most of tomorrow. However, an increase is expected late on the 22nd due to a glancing blow from today's partial halo CME. Conditions are expected to attain mostly active with some minor storm periods at high latitudes. There is a slight chance, however, for minor to major storm intervals if the CME should prove to be extraordinarily wide. Conditions should return to unsettled to active by the 24th. The greater than 10 MeV proton event should continue for at least 48 hours and the greater than 100 MeV proton event is expected to continue for the next 12-24 hours.
III. Event Probabilities 22 Apr to 24 Apr
Class M 35%25%20%
Class X 10%05%05%
PCAFin progress
IV. Penticton 10.7 cm Flux
  Observed       21 Apr 173
  Predicted    22 Apr-24 Apr  170/175/180
  90 Day Mean        21 Apr 200
V. Geomagnetic A Indices
  Observed Afr/Ap 20 Apr  030/062
  Estimated     Afr/Ap 21 Apr  007/007
  Predicted     Afr/Ap 22 Apr-24 Apr  015/015-025/030-015/020
VI. Geomagnetic Activity Probabilities 22 Apr to 24 Apr
A. Middle Latitudes
Minor storm 20%25%20%
Major-severe storm 15%20%15%
B. High Latitudes
Minor storm 25%30%25%
Major-severe storm 20%25%20%

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