Joint USAF/NOAA Report of Solar and Geophysical Activity 28 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 28 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 119 Issued at 2200Z on 28 Apr 2012

IA. Analysis of Solar Active Regions and Activity from 27/2100Z
to 28/2100Z: Solar activity was at low levels due to single,
low-level C-class events from Regions 1461 (N10W89), 1466 (N12W51),
1467 (N12E18), 1469 (S19E14) and new Region 1470 (S17E61). New
Region 1471 (S23E70) was also numbered during the period. A 16
degree filament eruption was observed in SDO/AIA 304 imagery at
28/1045Z. During the period of the eruption, the SE to NW oriented
filament was centered near S32W33. LASCO/C2 imagery observed an
associated slow-moving, non-Earth directed CME lifting off the SW
limb at 28/1224Z.

IB. Solar Activity Forecast: Solar activity is expected to be low
with a slight chance for M-class activity for the next three days
(29 April – 01 May).

IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z:
The geomagnetic field was at quiet to unsettled levels with an
isolated high latitude active period between 28/0900 – 1200Z.
Through the period, ACE solar wind velocities steadily decreased
from about 490 km/s to near 420km/s while the Bz component of the
interplanetary magnetic field was variable between +/-4 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 predominately quiet levels for days one and two
(29 – 30 April). By day three (01 May), quiet to unsettled levels,
with isolated active periods, are expected as a coronal hole high
speed stream moves into a geoeffective position.

III. Event Probabilities 29 Apr-01 May
Class M 20/20/20
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 28 Apr 121
Predicted 29 Apr-01 May 125/120/120
90 Day Mean 28 Apr 112

V. Geomagnetic A Indices
Observed Afr/Ap 27 Apr 007/008
Estimated Afr/Ap 28 Apr 005/005
Predicted Afr/Ap 29 Apr-01 May 004/005-004/005-007/008

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