Viewing archive of Thursday, 18 April 2002

Solar activity report

Report of Solar-Geophysical Activity 2002 Apr 18 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 108 Issued at 2200Z on 18 Apr 2002

IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z

Solar activity was low. Only C-class flares occurred over the past 24 hours. Some of these flares did not have an obvious source on the visible disk and may have originated from beyond the limb. Region 9906 (S14W55) remains large and complex but has shown some sunspot decay and magnetic simplification. New Regions 9911 (S13E23) and 9912 (N11E28) were numbered.
IB. Solar Activity Forecast
Solar activity is expected to be moderate. M-class activity is expected in Region 9906. A major flare in this region remains a possibility.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
The geomagnetic field ranged from quiet to severe storm levels in response to the CME that impacted the Earth early yesterday. ACE solar wind information suggests that this CME has passed. The geomagnetic field is currently at active levels. Yesterday's greater than 10 MeV proton event has ended: start 17/1530 UTC, maximum flux (24 pfu) 17/1540 UTC, and end 18/0035 UTC.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be at unsettled to active levels through the end of 18 April UTC. Another CME is expected to impact the Earth early on 19 April UTC from an LDE/CME that occurred on 17 April. Minor to major storm conditions are possible for the 24-48 hours following this CME's arrival. Geomagnetic activity is expected to decline to unsettled to active levels by the end of the 3-day forecast period. Another greater than 10 MeV proton event is possible if Region 9906 generates a major flare.
III. Event Probabilities 19 Apr to 21 Apr
Class M 75%50%40%
Class X 10%05%01%
IV. Penticton 10.7 cm Flux
  Observed       18 Apr 188
  Predicted    19 Apr-21 Apr  180/175/170
  90 Day Mean        18 Apr 201
V. Geomagnetic A Indices
  Observed Afr/Ap 17 Apr  027/041
  Estimated     Afr/Ap 18 Apr  045/050
  Predicted     Afr/Ap 19 Apr-21 Apr  040/040-030/050-012/020
VI. Geomagnetic Activity Probabilities 19 Apr to 21 Apr
A. Middle Latitudes
Minor storm 30%20%10%
Major-severe storm 20%10%05%
B. High Latitudes
Minor storm 40%30%20%
Major-severe storm 25%15%05%

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