Joint USAF/NOAA Report of Solar and Geophysical Activity 20 May 2008

Product: Report of Solar-Geophysical Activity
Issued: 2008 May 20 2200 UTC
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Weather Prediction Center and the U.S. Air Force.

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 141 Issued at 2200Z on 20 May 2008

IA. Analysis of Solar Active Regions and Activity from 19/2100Z to 20/2100Z: Solar activity was very low. No flares occurred during the past 24 hours. The two spotted regions on the disk were quiet and stable,

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

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z: The geomagnetic field was quiet to unsettled. A small increase in solar wind speed from around 360 km/s up to about 440 km/s occurred between 1200-1400Z. The solar wind signatures are consistent with a high speed stream from a coronal hole.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be unsettled to active with a chance for isolated minor storm periods for the first day (21 May) as the high speed stream is expected to continue. Observations of the solar wind at the Stereo-B spacecraft suggest that the solar wind velocity should increase to around 550-600 km/s. Activity levels are expected to decline to unsettled levels with occasional active periods for the second day (22 May) and should be predominantly unsettled for the third day (23 May).

III. Event Probabilities 21 May-23 May

• Class M 01/01/01
• Class X 01/01/01
• Proton 01/01/01
• PCAF Green

IV. Penticton 10.7 cm Flux

• Observed 20 May 069
• Predicted 21 May-23 May 068/068/068
• 90 Day Mean 20 May 071

V. Geomagnetic A Indices

• Observed Afr/Ap 19 May 005/008
• Estimated Afr/Ap 20 May 010/015
• Predicted Afr/Ap 21 May-23 May 015/025-008/015-008/010

VI. Geomagnetic Activity Probabilities 21 May-23 May

A. Middle Latitudes

• Active 40/25/25
• Minor storm 15/10/10
• Major-severe storm 05/01/01

B. High Latitudes

• Active 30/40/40
• Minor storm 35/20/20
• Major-severe storm 15/10/10