Joint USAF/NOAA Report of Solar and Geophysical Activity 03 Apr 2004

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

Updated 2004 Apr 03 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 094 Issued at 2200Z on 03 Apr 2004

IA. Analysis of Solar Active Regions and Activity from 02/2100Z
to 03/2100Z: Solar activity was at very low levels again today.
Region 582 (N14W51) continues to decay and has lost all penumbral
area in the trailing polarity of the region. Region 587 (S13W03)
has showed a slight decay since yesterday. Region 588 (S12E51)
underwent a little growth and currently has sunspots of opposite
polarity to the solar south of the dominant sunspot. No new regions
were numbered today.

IB. Solar Activity Forecast: Solar activity is expected to be at
very low to low levels.

IIA. Geophysical Activity Summary 02/2100Z to 03/2100Z:
The geomagnetic field ranged from quiet to minor storm levels. The
onset of a shock occurred at the ACE spacecraft at approximately
03/0849Z. Preliminary review indicates that there was a
magnetopause crossing of the GOES 12 satellite between 03/1630 and
1730Z. Interestingly, a sudden impulse which was measured as 14 nT
on the Boulder magnetometer occurred at 03/1414Z. The transient may
have been related to the full halo coronal mass ejection (CME) that
occurred on 31 March. Due to the SOHO/LASCO spacecraft maneuvers
that were in progress at the end of March (no images were being
retrieved) there is little certainty at this time as to whether this
shock passage was the result of the full halo CME or related to
other activity that preceded the long duration C3 event. The
greater than 2 MeV electron flux at geosynchronous orbit reached
high levels today.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at predominantly active levels for 4-5 April. During
the first two days, isolated minor storm conditions may persist
especially in the nighttime sectors, due to the potential of further
transient activity, and the likelihood of a recurrent co-rotating
interaction region. Major storm levels are expected due to a strong
recurrent high speed coronal hole stream that is due to become
geoeffective on 6 April.

III. Event Probabilities 04 Apr-06 Apr

• Class M 20/20/20
• Class X 01/01/01
• Proton 01/01/01
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 03 Apr 107
• Predicted 04 Apr-06 Apr 105/105/100
• 90 Day Mean 03 Apr 111

V. Geomagnetic A Indices

• Observed Afr/Ap 02 Apr 003/003
• Estimated Afr/Ap 03 Apr 015/023
• Predicted Afr/Ap 04 Apr-06 Apr 015/020-015/020-025/035

VI. Geomagnetic Activity Probabilities 04 Apr-06 Apr

A. Middle Latitudes

• Active 30/30/45
• Minor storm 15/15/30
• Major-severe storm 10/10/15

B. High Latitudes

• Active 45/45/30
• Minor storm 25/25/45
• Major-severe storm 15/15/25