Report of Solar-Geophysical Activity

Issued: 2012 Apr 23 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 114 Issued at 2200Z on 23 Apr 2012

IA.  Analysis of Solar Active Regions and Activity from  22/2100Z
to 23/2100Z:  Solar activity has been at low levels for the past 24
hours. There are currently 8 active regions on the disk, with 5
regions having sunspots. The spotted regions on the disk all
remained rather quiet and stable throughout the period. However,
around plage Region 1461 (N10W19), two C-class events were observed
today with associated Earth directed CME's.
IB.  Solar Activity Forecast:  Solar activity is expected to be at
low levels with a chance for M-class x-ray events for the next three
days (24 - 26 April).
IIA.  Geophysical Activity Summary 22/2100Z to 23/2100Z:
The geomagnetic field has been at quiet to minor storm levels for the
past 24 hours. Observations made by the ACE spacecraft, around
23/0200Z, indicated the arrival of a CME that lifted off the solar
disk on 19 April. Solar wind velocities increased from 350 - 400
km/s with the total IMF reaching around 18 nT. The Boulder
magnetometer measured a 31 nT sudden impulse at 23/0325Z in
conjunction with the CME arrival here at Earth. From then on, active
to minor storm levels were observed due to multiple periods of
sustained negative Bz.
IIB.  Geophysical Activity Forecast:  The geomagnetic field is
expected to be at quiet to active levels with a slight chance for a
minor storm on day 1 (24 April) as effects from the CME wane and a
coronal hole high speed stream (CH HSS) moves in. Quiet to active
levels are expected on day two (25 April) as the effects of the CH
HSS continue.  An increase to quiet to minor storm levels are
expected on day three (26 April) as the two CMEs, observed earlier
in the period, are expected to become geoeffective.
III.  Event Probabilities 24 Apr-26 Apr
Class M    30/30/30
Class X    01/01/01
Proton     01/01/01
PCAF       green
IV.  Penticton 10.7 cm Flux
Observed           23 Apr 142
Predicted   24 Apr-26 Apr  140/140/135
90 Day Mean        23 Apr 112
V.  Geomagnetic A Indices
Observed Afr/Ap 22 Apr  007/008
Estimated Afr/Ap 23 Apr  016/025
Predicted Afr/Ap 24 Apr-26 Apr  012/018-008/012-011/018
VI.  Geomagnetic Activity Probabilities 24 Apr-26 Apr
A.  Middle Latitudes
Active                40/25/40
Minor storm           15/05/15
Major-severe storm    01/01/01
B.  High Latitudes
Active                50/40/50
Minor storm           30/20/30
Major-severe storm    10/05/10