Joint USAF/NOAA Report of Solar and Geophysical Activity 27 Apr 2004

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

Updated 2004 Apr 27 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 118 Issued at 2200Z on 27 Apr 2004

IA. Analysis of Solar Active Regions and Activity from 26/2100Z
to 27/2100Z: Solar activity has been low. Region 599 (N14E02)
produced a C3.1 flare at 27/0723 UTC with an associated Type II
flare with a speed of 732 km/s. LASCO imagery was not available, but
EIT imagery indicated significant dimming in the area of Region 599,
suggesting the existence of a CME. No significant development was
observed on regions on the visible disk, and no new regions were
numbered.

IB. Solar Activity Forecast: Solar activity is expected to be very
low to low. Region 599 has the potential to produce C- and isolated
M-class flares.

IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z:
The geomagnetic field has been quiet to unsettled.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to unsettled, with isolated active or minor
storm conditions possible on day three (30 April) from a CME
associated with the C3 flare observed today.

III. Event Probabilities 28 Apr-30 Apr

• Class M 10/10/10
• Class X 01/01/01
• Proton 01/01/01
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 27 Apr 095
• Predicted 28 Apr-30 Apr 095/090/090
• 90 Day Mean 27 Apr 107

V. Geomagnetic A Indices

• Observed Afr/Ap 26 Apr 004/007
• Estimated Afr/Ap 27 Apr 005/007
• Predicted Afr/Ap 28 Apr-30 Apr 005/008-005/008-010/020

VI. Geomagnetic Activity Probabilities 28 Apr-30 Apr

A. Middle Latitudes

• Active 15/15/20
• Minor storm 10/10/15
• Major-severe storm 05/05/10

B. High Latitudes

• Active 20/20/25
• Minor storm 15/15/20
• Major-severe storm 10/05/10