Joint USAF/NOAA Report of Solar and Geophysical Activity 13 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 13 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 104 Issued at 2200Z on 13 Apr 2012

IA. Analysis of Solar Active Regions and Activity from 12/2100Z
to 13/2100Z: Solar activity was very low. Region 1455 (N07W19)
produced occasional B-class x-ray flares. It showed gradual spot and
penumbral growth during the period as well as a mix of polarities in
its intermediate and trailer portions, which indicated a beta-gamma
magnetic structure. New Region 1457 (N22E41) was numbered.

IB. Solar Activity Forecast: Solar activity is expected to be very
low during days 1 – 3 (14 – 16 April) with a chance for isolated
C-class flares from Region 1455.

IIA. Geophysical Activity Summary 12/2100Z to 13/2100Z:
Geomagnetic field activity ranged from quiet to minor storm levels
with a brief period of major storm at high latitudes. The increased
field activity was associated with a persistent coronal hole
high-speed stream (CH HSS). Solar winds speeds gradually increased
during the first half of the period (maximum speed 693 km/s at
13/0846Z), then gradually decreased during the second half of the
period (minimum speed 544 km/s at 13/1941Z).

IIB. Geophysical Activity Forecast: Geomagnetic field activity is
expected to be at quiet to unsettled levels during days 1 – 2 (14 –
15 April) with a chance for active levels due to persistent CH HSS
effects. Activity is expected to decrease to mostly quiet levels on
day 3 (16 April) as the CH HSS subsides.

III. Event Probabilities 14 Apr-16 Apr
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 13 Apr 098
Predicted 14 Apr-16 Apr 100/100/100
90 Day Mean 13 Apr 114

V. Geomagnetic A Indices
Observed Afr/Ap 12 Apr 011/014
Estimated Afr/Ap 13 Apr 014/020
Predicted Afr/Ap 14 Apr-16 Apr 007/012-010/012-004/005

VI. Geomagnetic Activity Probabilities 14 Apr-16 Apr
A. Middle Latitudes
Active 30/25/15
Minor storm 20/15/05
Major-severe storm 01/01/01
B. High Latitudes
Active 35/30/20
Minor storm 25/20/10
Major-severe storm 01/01/01