Joint USAF/NOAA Report of Solar and Geophysical Activity 28 May 2003

SDF Number 148 Issued at 2200Z on 28 May 2003

IA. Analysis of Solar Active Regions and Activity from 27/2100Z
to 28/2100Z: Solar activity increased to high levels today. Region
365 (S07W32) produced two X-class flares early in the period. The
first was an X1.3/2b flare that occurred at 27/2307Z with an
associated Tenflare (910 sfu), Type IV, and Type II (estimated shock
velocity of 607 km/s.) radio sweep. The second, larger flare, an
X3.6 x-ray event which occurred at 28/0027Z that also had an
associated Tenflare (1600 sfu), Type IV, and Type II (estimated 392
km/s.) radio sweep. Both flares had associated CME’s (based on
LASCO imagery) that appear to be Earth directed. This region
continues to show good growth and remains a beta-gamma-delta
magnetic complex. Little activity was noted from the rest of the
disk. Region 374 (S22W59) was newly assigned today.

IB. Solar Activity Forecast: Solar activity is expected to be at
moderate to high levels. Region 365 is very capable of producing
major flare activity.

IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z:
The geomagnetic field was at active to major storm levels. A
recurrent high speed stream coronal hole is responsible for the
elevated levels. The greater than 10 MeV proton fluxes have been
just under event threshold levels for the past several hours of this
period. The greater than 2 MeV electron fluxes at geosynchronous
orbit reached moderate levels today.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at predominantly active to minor storm levels through
the forecast period. Transient activity from today’s X-flares is
expected by day two of the interval with resulting major to severe
storm conditions possible. The greater than 10 MeV proton fluxes at
geosynchronous orbit may reach threshold levels on day one of the
period.

III. Event Probabilities 29 May-31 May

• Class M 75/75/75
• Class X 25/25/25
• Proton 80/50/25
• PCAF green

IV. Penticton 10.7 cm Flux

• Observed 28 May 130
• Predicted 29 May-31 May 135/140/135
• 90 Day Mean 28 May 125

V. Geomagnetic A Indices

• Observed Afr/Ap 27 May 018/026
• Estimated Afr/Ap 28 May 025/038
• Predicted Afr/Ap 29 May-31 May 025/025-040/050-015/025

VI. Geomagnetic Activity Probabilities 29 May-31 May

A. Middle Latitudes

• Active 50/35/40
• Minor storm 25/35/20
• Major-severe storm 15/25/10

B. High Latitudes

• Active 45/30/45
• Minor storm 30/35/30
• Major-severe storm 20/35/20