Joint USAF/NOAA Report of Solar and Geophysical Activity 27 Apr 2003
SDF Number 117 Issued at 2200Z on 27 Apr 2003
IA. Analysis of Solar Active Regions and Activity from 26/2100Z
to 27/2100Z: Solar activity decreased to moderate levels. Region
338 (N18W85) produced an M2.5/Sf at 26/2340Z and an M1.7/Sf at
27/1532Z which were the largest flares of the period. This region
was again responsible for the vast majority of the activity observed
today. Proximity to the west limb hinders analysis of changes in
magnetic structure today. Region 344 (N16W00) showed slight growth
today and retains a beta-gamma-delta structure. The weak delta
complex is evident in the northwestern quadrant of the dominant
trailing spot. Region 337 (S14W40) underwent rapid growth during
the period adding many additional spots to the south of the main
body of this group. This region also depicts a beta-gamma-delta
magnetic structure. A 34 degree solar filament erupted yesterday at
approximately 26/2000Z which resulted in a streamer CME that does
not appear as though it will become geoeffective No new regions
were numbered today.
IB. Solar Activity Forecast: Solar activity is expected to be at
moderate levels. Region 338 has begun to transit the disk but
remains capable of producing a major flare.
IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z:
The geomagnetic field was at quiet to active levels. An increase of
150 km/s in the solar wind speed during the period is believed to be
the result of a recurrent coronal hole. The greater than 2 MeV
electron fluxes at geosynchronous orbit reached high levels again
today.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at predominantly unsettled to active levels through
the interval. High latitude minor storm conditions are possible on
day one and into day two due to a favorably positioned coronal hole.
III. Event Probabilities 28 Apr-30 Apr
- Class M 70/50/50
- Class X 15/10/05
- Proton 05/01/01
- PCAF green
IV. Penticton 10.7 cm Flux
- Observed 27 Apr 154
- Predicted 28 Apr-30 Apr 155/160/155
- 90 Day Mean 27 Apr 127
V. Geomagnetic A Indices
- Observed Afr/Ap 26 Apr 009/015
- Estimated Afr/Ap 27 Apr 012/012
- Predicted Afr/Ap 28 Apr-30 Apr 015/015-012/015-012/015
VI. Geomagnetic Activity Probabilities 28 Apr-30 Apr
A. Middle Latitudes
- Active 35/30/25
- Minor storm 20/15/10
- Major-severe storm 10/05/05
B. High Latitudes
- Active 45/35/30
- Minor storm 30/25/15
- Major-severe storm 15/10/05
