Joint USAF/NOAA Report of Solar and Geophysical Activity 21 Apr 2006

Product: Report of Solar-Geophysical Activity
Issued: 2006 Apr 21 2200 UTC
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 111 Issued at 2200Z on 21 Apr 2006

IA. Analysis of Solar Active Regions and Activity from 20/2100Z to 21/2100Z: Solar activity continued very low. Region 874 (S01W25), the sole spotted region visible, was stable and quiet. There are signs of new flux emerging in the southeast, where two small groups are in the formative stage. The limbs were quiet.

IB. Solar Activity Forecast: Solar activity is expected to be very low to low.

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z: The geomagnetic field was quiet to active. A period of enhanced solar wind conditions began around midday, when Alfven waves caused Bz to reach -10 nT for a brief period. Those fluctuations are still occurring. The greater than 2 MeV electron flux at GOES was again at high levels.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be predominantly quiet to unsettled for the next three days. Solar wind wave activity may persist for the next few hours, and there is a chance of another short-lived disturbance from high-speed solar wind on April 23.

III. Event Probabilities 22 Apr-24 Apr

• Class M 05/05/05
• Class X 01/01/01
• Proton 01/01/01
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 21 Apr 079
• Predicted 22 Apr-24 Apr 080/080/085
• 90 Day Mean 21 Apr 078

V. Geomagnetic A Indices

• Observed Afr/Ap 20 Apr 003/005
• Estimated Afr/Ap 21 Apr 006/008
• Predicted Afr/Ap 22 Apr-24 Apr 005/008-010/010-005/008

VI. Geomagnetic Activity Probabilities 22 Apr-24 Apr

A. Middle Latitudes

• Active 15/20/15
• Minor storm 01/05/01
• Major-severe storm 01/01/01

B. High Latitudes

• Active 20/20/20
• Minor storm 05/10/05
• Major-severe storm 01/01/01