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

Updated 2005 May 09 0120 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity SDF Number 128 Issued at 2200Z on 08 May 2005

IA. Analysis of Solar Active Regions and Activity from 07/2100Z to 08/2100Z: Solar activity was low. There was one C-class event at 0928 UTC from newly numbered Region 759 (N12E71). The group so far appears to be a moderately large D-type sunspot group. A CME was observed moving off the west limb at 1630 UTC but appears to be from the backside of the disk.

IB. Solar Activity Forecast: Solar activity is expected to be low. There is a slight chance for an isolated M-class event during the next three days.

IIA. Geophysical Activity Summary 07/2100Z to 08/2100Z: The geomagnetic field ranged from active to major storm levels during the past 24 hours with a severe storm period at high latitudes from 1200-1500 UTC. Magnetopause crossings were seen at GOES-12 at about 1330 UTC and 1610 UTC. Solar wind speed increased during the past 24 hours with peak values just below 900 km/s from 0900-1300 UTC. Intervals of strongly negative Bz were seen around 07/2100-08/0100 UTC and again from 0900-1300 UTC. The solar wind signatures appear to indicate the onset of a coronal hole high speed stream which has been modified by transient flow from the CME of 06/1728 UTC. The greater than 10 MeV protons gradually decayed from enhanced levels to nearly background level by forecast issue time.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at active to minor storm levels for the next two days (09-10 May) as the current disturbance persists. Conditions are expected to subside to mostly unsettled levels by the third day (11 May).

III. Event Probabilities 09 May-11 May

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

IV. Penticton 10.7 cm Flux

• Observed 08 May 101
• Predicted 09 May-11 May 100/100/100
• 90 Day Mean 08 May 093

V. Geomagnetic A Indices

• Observed Afr/Ap 07 May 010/010
• Estimated Afr/Ap 08 May 040/070
• Predicted Afr/Ap 09 May-11 May 025/030-020/030-010/015

VI. Geomagnetic Activity Probabilities 09 May-11 May

A. Middle Latitudes

• Active 20/30/25
• Minor storm 35/25/15
• Major-severe storm 30/20/10

B. High Latitudes

• Active 15/25/35
• Minor storm 35/35/20
• Major-severe storm 40/30/15

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