Joint USAF/NOAA Report of Solar and Geophysical Activity 18 Apr 2009

Product: Report of Solar-Geophysical Activity
Issued: 2009 Apr 18 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 108 Issued at 2200Z on 18 Apr 2009

IA. Analysis of Solar Active Regions and Activity from 17/2100Z
to 18/2100Z: Solar activity was very low. No flares were observed
during the past 24 hours. The visible disk remains spotless.

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

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z:
The geomagnetic field was at quiet to unsettled levels. Observations
from the ACE spacecraft show solar wind speeds gradually increased
through the period from about 400 km/s to near 550 km/s with IMF Bz
fluctuations around +/- 5nT, all due to continued effects from a
coronal hole high speed stream.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly quiet for 19 – 20 April as the coronal hole
high speed stream will have rotated out of a geoeffective position.
Quiet to unsettled levels are expected for 21 April due to a
recurrent enhancement in solar wind velocities.

III. Event Probabilities 19 Apr-21 Apr
Class M 01/01/01
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 18 Apr 070
Predicted 19 Apr-21 Apr 070/070/070
90 Day Mean 18 Apr 070

V. Geomagnetic A Indices
Observed Afr/Ap 17 Apr 004/005
Estimated Afr/Ap 18 Apr 007/007
Predicted Afr/Ap 19 Apr-21 Apr 005/005-005/005-008/010

VI. Geomagnetic Activity Probabilities 19 Apr-21 Apr
A. Middle Latitudes
Active 05/05/15
Minor storm 01/01/05
Major-severe storm 01/01/01
B. High Latitudes
Active 05/05/20
Minor storm 01/01/05
Major-severe storm 01/01/01