Joint USAF/NOAA Report of Solar and Geophysical Activity 26 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 26 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 117 Issued at 2200Z on 26 Apr 2012

IA. Analysis of Solar Active Regions and Activity from 25/2100Z
to 26/2100Z: Solar activity was at low levels. Region 1460 (N15W93)
and Region 1465 (S18W39) both produced C1 x-ray events at 25/2242Z
and 26/1723Z respectively. Both had associated CMEs but neither are
expected to be geoeffective. Three consecutive CMEs appeared on
LASCO/C2 imagery at 26/0924Z, 26/1148Z, and 26/1638Z. All three
were around the west limb and are not expected to be geoeffective.

IB. Solar Activity Forecast: Solar activity is expected to remain
low with a slight chance for M-class activity for the next three
days (27 – 29 April).

IIA. Geophysical Activity Summary 25/2100Z to 26/2100Z:
The geomagnetic field started the period at minor storm levels, but
fell to quiet levels and remained mostly quiet for the remainder of
the period. This activity was attributed to Coronal Hole High Speed
Stream (CH HSS) effects. Solar wind speeds have steadily decreased
from approximately 730 km/s to approximately 560 km/s. The Bz
component of the interplanetary magnetic field has remained fairly
neutral with minor fluctuations between +3 and -5 nT. Overall, the
total field fluctuated between +2 and +8 nT. The greater than 2 MeV
electron flux at geosynchronous orbit was at high levels throughout
the period.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to unsettled levels with isolated active
periods for day one (27 April) as CH HSS effects begin to wane.
Days two and three (28 -29 April) are expected to be mostly quiet.

III. Event Probabilities 27 Apr-29 Apr
Class M 15/15/15
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 26 Apr 119
Predicted 27 Apr-29 Apr 115/110/105
90 Day Mean 26 Apr 112

V. Geomagnetic A Indices
Observed Afr/Ap 25 Apr 018/031
Estimated Afr/Ap 26 Apr 013/017
Predicted Afr/Ap 27 Apr-29 Apr 007/010-004/005-004/005

VI. Geomagnetic Activity Probabilities 27 Apr-29 Apr
A. Middle Latitudes
Active 20/10/10
Minor storm 05/01/01
Major-severe storm 01/01/01
B. High Latitudes
Active 15/15/15
Minor storm 25/15/15
Major-severe storm 25/10/10