Viewing archive of Wednesday, 4 April 2001

Solar activity report

Report of Solar-Geophysical Activity 2001 Apr 04 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 094 Issued at 2200Z on 04 Apr 2001

IA. Analysis of Solar Active Regions and Activity from 03-2100Z to 04-2100Z

Solar activity was moderate due to four M-class events during the past 24 hours. The largest of these was an M2 at 1222Z. The event could not be attributed to a specific region on the Sun due to limited observations. The other M-class events were an M1/Sf at 03/2351Z from 9415 (S21E60), an M1/Sf at 1027Z from 9415 again, and an M1/Sf at 1159Z from Region 9401 (N24W70). Region 9393 (N18W90+) has rotated around the west limb. Region 9415 (S21E60) now is the largest, most active region on the disk with an area of 680 millionths in a DKO beta-gamma configuration. A 25 degree filament near N30E25 disappeared during the past 24 hours. Two CMEs were observed on the east limb at 03/1950Z and 04/0950Z: corresponding EIT images indicated back-sided sources behind the east limb.
IB. Solar Activity Forecast
Solar activity is expected to be mostly moderate. There is a chance for an isolated major flare during the next three days, with higher probabilities during the next 24 hours while region 9393 is not too far beyond west limb.
IIA. Geophysical Activity Summary 03-2100Z to 04-2100Z
The geomagnetic field was quiet until a sudden impulse occurred at 1455Z. The impulse resulted from a shock in the solar wind which was initially observed at ACE at 1422Z. After the shock the solar wind displayed high speeds and strong fluctuations of the magnetic component Bz (peak values were around +/- 20 nT). This disturbed solar wind produced active to minor storm levels of geomagnetic activity. Bz stabilized into a steady northward orientation around 1830Z and geomagnetic activity levels seemed to be calming in response. The shock and subsequent enhanced solar wind flow are most likely to have been produced by the combined drivers from CMEs out of region 9393 on April 2. The greater than 10 MeV proton event continues to be in progress. The shock passage produced a very slight enhancement of the particle flux levels. The flux at 04/2100Z was 113 pfu.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be at active to minor storm levels during the next 24 hours. Solar wind speeds and temperatures are still enhanced, and there is still a possibility for more intervals of geoeffective solar wind during the next 24 hours. The second day is forecast to be active, based on the possible impact of a glancing blow from the CME that originated from region 9415 on 3 April. Mostly unsettled levels should prevail by day three.
III. Event Probabilities 05 Apr to 07 Apr
Class M80%65%65%
Class X30%20%20%
PCAFin progress
IV. Penticton 10.7 cm Flux
  Observed       04 Apr 205
  Predicted   05 Apr-07 Apr  200/190/180
  90 Day Mean        04 Apr 167
V. Geomagnetic A Indices
  Observed Afr/Ap 03 Apr  005/005
  Estimated     Afr/Ap 04 Apr  025/020
  Predicted    Afr/Ap 05 Apr-07 Apr  030/030-020/025-015/015
VI. Geomagnetic Activity Probabilities 05 Apr to 07 Apr
A. Middle Latitudes
Minor storm30%25%20%
Major-severe storm20%15%05%
B. High Latitudes
Minor storm30%15%20%
Major-severe storm25%25%05%

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