Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 19 Sep 2004

By SpaceRef Editor

September 19, 2004

Filed under Space Weather Prediction Center (NOAA), Space Weather Solar-Geophysical Activity, US

Prepared jointly by the U.S. Dept. of Commerce, NOAA,

Space Environment Center and the U.S. Air Force.
Updated 2004 Sep 19 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 263 Issued at 2200Z on 19 Sep 2004

IA. Analysis of Solar Active Regions and Activity from 18/2100Z
to 19/2100Z: Solar activity was moderate. Region 672 (N05W58), which
has been in a decay phase over the last 72 hours, produced two
notable events this period. The first was an extended C3.8 flare at
19/1148Z that erupted along a filament channel just north of the
spot cluster. The second was an M1.9 flare at 19/1712Z. This
impressive flare had associated Type II (604 km/s) and Type IV radio
sweeps; a 520 sfu Tenflare, and a greater than 10 MeV proton event.
LASCO imagery was unavailable. Region 672 is a C-type beta spot
group with under 100 millionths of white light area coverage. Region
673 (S13E22) showed little change this period and continues to
produce occasional B-class flare activity.

IB. Solar Activity Forecast: Solar activity is expected to be low
to very low. There is a small chance of another M-class flare from
Region 672 before it rotates around the west limb early on 22
September. Occasional C-class flares are possible from Region 673.

IIA. Geophysical Activity Summary 18/2100Z to 19/2100Z:
The geomagnetic field was quiet. Solar wind speed was generally below
400 km/s. A greater than 10 MeV proton event followed today’s M1
flare at 19/1712Z. The proton event began at 19/1925Z and was still
in progress at the time of issue. The maximum flux value so far was
35 pfu at 19/2025Z. A greater than 100 MeV proton flux enhancement
was also observed, but has not exceeded the 1 pfu event threshold.
The greater than 2 MeV electron flux at geosynchronous orbit was at
high levels.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to remain at mostly quiet to unsettled levels on 20 and 21
September. Occasional active periods are possible at high latitudes.
A disturbance associated with today’s M1 flare and CME is expected
to occur on 22 September: Active to minor storm periods are likely.
The greater than 10 MeV proton event in progress now is expected to
end by 21 September.

III. Event Probabilities 20 Sep-22 Sep