Joint USAF/NOAA Report of Solar and Geophysical Activity 18 April 2012

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Weather Prediction Center and the U.S. Air Force.
Updated 2012 Apr 18 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 109 Issued at 2200Z on 18 Apr 2012

IA. Analysis of Solar Active Regions and Activity from 17/2100Z
to 18/2100Z: Solar activity was low during the past 24 hours. New
Region 1463 (S26W36) produced several C-class and optical flares,
the largest a C8/Sf at 18/1239Z. An associated CME became visible in
STEREO COR2 imagery at 18/1309Z. Further analysis will be conducted
to determine effectiveness as imagery becomes available. Region 1463
also produced a C5 flare at 18/1706Z associated with Type II (est.
speed 621 km/s) and Type IV radio sweeps. No STEREO or LASCO imagery
was available for this event. Further analysis will also be
conducted on this event when imagery is available.

IB. Solar Activity Forecast: Solar activity is expected to be low
with a slight chance for an isolated M-class event for the next
three days (19-21 April).

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z:
The geomagnetic field was quiet to unsettled during the past 24
hours. The increase in activity was due to a slight increase in
solar wind speeds (reaching approximately 475 km/s) and extended
periods of southward Bz.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly quiet on day one (19 April). Quiet to
unsettled conditions are expected on day two (20 April) due to an
anticipated Solar Sector Boundary Crossing. A return to mostly quiet
conditions is expected on day three (21 April).

III. Event Probabilities 19 Apr-21 Apr
Class M 15/15/15
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 18 Apr 122
Predicted 19 Apr-21 Apr 120/120/120
90 Day Mean 18 Apr 112

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

VI. Geomagnetic Activity Probabilities 19 Apr-21 Apr
A. Middle Latitudes
Active 10/25/10
Minor storm 01/10/01
Major-severe storm 01/01/01
B. High Latitudes
Active 15/15/15
Minor storm 15/30/15
Major-severe storm 10/30/10