Joint USAF/NOAA Report of Solar and Geophysical Activity 25 Apr 2005

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2005 Apr 25 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 115 Issued at 2200Z on 25 Apr 2005

IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity continues at very low levels. New Region
756 (S06E68) is rotating into view on the southeast limb. Although
this region’s close proximity to the limb is hindering the analysis,
it does appear to be a moderate size sunspot group, with initial
measurements of over 400 millionths in white light area. The CME
activity on 22 April may have been associated with this region;
however, activity in the past 48 hours was limited to occasional
B-class flares. No other activity of note occurred this period.

IB. Solar Activity Forecast: Solar activity is expected to be very
low to low. Region 756 has the potential to produce C-class flares.

IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field was quiet to unsettled with isolated active
periods at high latitudes. The weak high speed stream in progress
since 23 April is declining. Solar wind speed ended the period at
around 480 km/s.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to unsettled.

III. Event Probabilities 26 Apr-28 Apr

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

IV. Penticton 10.7 cm Flux

• Observed 25 Apr 086
• Predicted 26 Apr-28 Apr 090/100/100
• 90 Day Mean 25 Apr 090

V. Geomagnetic A Indices

• Observed Afr/Ap 24 Apr 005/010
• Estimated Afr/Ap 25 Apr 008/010
• Predicted Afr/Ap 26 Apr-28 Apr 005/008-005/005-005/005

VI. Geomagnetic Activity Probabilities 26 Apr-28 Apr

A. Middle Latitudes

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

B. High Latitudes

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