Joint USAF/NOAA Report of Solar and Geophysical Activity 10 Apr 2004
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.
Updated 2004 Apr 10 2230 UTC
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 101 Issued at 2200Z on 10 Apr 2004
IA. Analysis of Solar Active Regions and Activity from 09/2100Z
to 10/2100Z: Solar activity was very low. Region 588 (S15W38)
contains the only sunspots on the visible disk. This region
maintains a reverse polarity beta magnetic configuration, but has
been quiet since producing a C2 flare and CME at 09/2040Z. No other
significant activity or changes were observed.
IB. Solar Activity Forecast: Solar activity is expected to be low
to very low. Isolated C-class flares are possible from Region 588.
IIA. Geophysical Activity Summary 09/2100Z to 10/2100Z:
The geomagnetic field was quiet to unsettled. Solar wind speed was in
gradual decline following yesterday’s CME impact. Speed declined
from a peak near 570 km/s at 09/0505Z to near 400 km/s late in the
period. A sharp discontinuity in solar wind plasma and IMF
measurements occurred at 10/1925Z. This was likely the
interplanetary shock associated with the C7 flare and CME on 08
April. Solar wind speed following the shock ranged from 500 to 540
km/s, but the IMF BZ was mostly northward. The greater than 2 MeV
electron flux at geosynchronous orbit reached high levels again this
period.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to active. Occasional active periods are
expected on 11 April following today’s CME arrival. Updated LASCO
imagery reveal another Earth-directed CME associated with
yesterday’s C2 flare at 09/2040Z. A geomagnetic response is likely
on 12 April, but the disturbance should be limited to occasional
active periods. Mostly quiet to unsettled conditions are expected on
13 April.
III. Event Probabilities 11 Apr-13 Apr
- Class M 05/10/10
- Class X 01/01/01
- Proton 01/01/01
- PCAF green
IV. Penticton 10.7 cm Flux
- Observed 10 Apr 088
- Predicted 11 Apr-13 Apr 090/095/100
- 90 Day Mean 10 Apr 109
V. Geomagnetic A Indices
- Observed Afr/Ap 09 Apr 011/016
- Estimated Afr/Ap 10 Apr 015/012
- Predicted Afr/Ap 11 Apr-13 Apr 020/025-015/018-012/015
VI. Geomagnetic Activity Probabilities 11 Apr-13 Apr
A. Middle Latitudes
- Active 40/30/15
- Minor storm 25/10/05
- Major-severe storm 15/01/01
B. High Latitudes
- Active 45/35/25
- Minor storm 35/15/10
- Major-severe storm 20/05/01
