Prepared jointly by the U.S. Dept. of Commerce, NOAA, Space Environment Center and the U.S. Air Force. Updated 2005 May 15 2230 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity SDF Number 135 Issued at 2200Z on 15 May 2005

IA. Analysis of Solar Active Regions and Activity from 14/2100Z to 15/2100Z: Solar activity was low. Several low level C-flares were produced by Regions 758 (S10 on the west limb) and 763 (S15E16). Region 759 (N11W20) has decayed slightly over the past 24 hours. A CME off the west limb with a speed of approximately 580 km/s was seen on LASCO imagery at 14/2122 UTC associated with a long duration C2.8 which occurred at 14/2058 UTC from Region 758. At the time of issue, the greater than 10 MeV proton flux at geosynchronous orbit was at 3.4 PFU as of 15/2135 UTC.

IB. Solar Activity Forecast: Solar activity is expected to be at low to moderate levels. Region 759 is still capable of producing an M-class event.

IIA. Geophysical Activity Summary 14/2100Z to 15/2100Z: The geomagnetic field was at quiet to severe storm levels. The arrival of a CME from 13 May initiated the disturbance which caused severe storming conditions between 15/0600 UTC and 0900 UTC. Solar wind speed at ACE increased from approximately 200 km/s to 950 km/s. Solar wind speed has declined to approximately 750 km/s by the end of the period. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels again today.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at unsettled to minor storm levels on 16 May. On 17 May, a possible glancing blow from the 14 May CME along with a recurrent coronal hole high speed stream are expected to become geoeffective causing unsettled to active conditions. Quiet to unsettled conditions are expected on 18 May.

III. Event Probabilities 16 May-18 May

• Class M 40/35/30
• Class X 05/05/05
• Proton 40/10/05
• PCAF yellow

IV. Penticton 10.7 cm Flux

• Observed 15 May 103
• Predicted 16 May-18 May 100/100/100
• 90 Day Mean 15 May 093

V. Geomagnetic A Indices

• Observed Afr/Ap 14 May 004/008
• Estimated Afr/Ap 15 May 075/100
• Predicted Afr/Ap 16 May-18 May 020/040-012/015-008/010

VI. Geomagnetic Activity Probabilities 16 May-18 May

A. Middle Latitudes

• Active 30/25/20
• Minor storm 25/10/10
• Major-severe storm 15/01/01

B. High Latitudes

• Active 25/25/20
• Minor storm 30/15/10
• Major-severe storm 25/05/01

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