Issued: 2007 Apr 23 2200 UTC

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

Joint USAF/NOAA Report of Solar and Geophysical Activity SDF Number 113 Issued at 2200Z on 23 Apr 2007

IA. Analysis of Solar Active Regions and Activity from 22/2100Z to 23/2100Z: Solar activity was very low. The visible solar disk remains spotless.

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

IIA. Geophysical Activity Summary 22/2100Z to 23/2100Z:

The geomagnetic field ranged from quiet to active with a single minor storm period at all latitudes from 23/0300 - 0600Z. The solar wind speed reached approximately 550 km/s today due to a recurrent coronal hole high speed stream, but dropped below 450 km/s by the end of the reporting period.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be quiet to unsettled for the next three days (24 - 26 April).

III. Event Probabilities 24 Apr-26 Apr

Class M 01/01/01

Class X 01/01/01

Proton 01/01/01

PCAF Green

IV. Penticton 10.7 cm Flux

Observed 23 Apr 069

Predicted 24 Apr-26 Apr 070/070/070

90 Day Mean 23 Apr 074

V. Geomagnetic A Indices

Observed Afr/Ap 22 Apr 008/010

Estimated Afr/Ap 23 Apr 012/018

Predicted Afr/Ap 24 Apr-26 Apr 005/008-005/005-005/005 VI. Geomagnetic Activity Probabilities 24 Apr-26 Apr A. Middle Latitudes

Active 15/10/10

Minor storm 05/05/05

Major-severe storm 01/01/01

B. High Latitudes

Active 20/15/15

Minor storm 05/05/05

Major-severe storm 01/01/01

Summary For April 16-22

No space weather storms were observed during the summary period.

Outlook For April 25-May 1

Category G1 (minor) geomagnetic storms are possible on 28 April due to a high-speed solar wind stream from a coronal hole.