Joint USAF/NOAA Report of Solar and Geophysical Activity 25 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 25 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 116 Issued at 2200Z on 25 Apr 2012

IA. Analysis of Solar Active Regions and Activity from 24/2100Z
to 25/2100Z: Solar activity was at low levels. Region 1459 (S16W65)
produced a C1 x-ray event at 25/0224Z while Region 1460 (N15W81)
produced a C3/Sf at 25/1215Z. Region 1465 (S17W26) indicated
consolidation in both its leader and trailer spots. The region
appeared to have lost its gamma and delta magnetic configuration,
but still maintained an east to west oriented inversion line. No
discernible changes were noted in the remaining regions. No
Earth-directed CMEs were observed during the period.

IB. Solar Activity Forecast: Solar activity is expected to remain
at low levels with a slight chance for M-class activity for the next
three days (26 – 28 April).

IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z:
The geomagnetic field ranged from quiet to minor storm conditions
with an isolated high latitude severe storm period observed during
25/0600Z – 0900Z. This activity was due to coronal hole high speed
stream affects (CH HSS). Over the past 24 hours, solar wind
velocities gradually increased from about 600 km/s to near 800 km/s.
Total field strength (Bt) varied between 5 to 12 nT while the Bz
component of the interplanetary magnetic field remained mostly south
from -4 to -10 nT. The greater than 2 MeV electron flux at
geosynchronous orbit reached high levels during the period.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at quiet to active levels with isolated minor storm
periods on day one (26 April) as the 23 April CME is expected to
become geoeffective. Quiet to unsettled levels with isolated active
periods are expected on day two (27 April) as effects of the CME
wane. By day three (28 April), mostly quiet conditions are expected.

III. Event Probabilities 26 Apr-28 Apr
Class M 20/20/20
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 25 Apr 127
Predicted 26 Apr-28 Apr 125/120/120
90 Day Mean 25 Apr 112

V. Geomagnetic A Indices
Observed Afr/Ap 24 Apr 030/043
Estimated Afr/Ap 25 Apr 018/022
Predicted Afr/Ap 26 Apr-28 Apr 017/025-011/015-004/006

VI. Geomagnetic Activity Probabilities 26 Apr-28 Apr
A. Middle Latitudes
Active 50/25/10
Minor storm 20/10/01
Major-severe storm 10/05/01
B. High Latitudes
Active 40/30/10
Minor storm 30/15/01
Major-severe storm 15/10/01