Report of Solar-Geophysical Activity
Issued: 2011 Apr 28 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 118 Issued at 2200Z on 28 Apr 2011
IA. Analysis of Solar Active Regions and Activity from 27/2100Z
to 28/2100Z: Solar activity has been at low levels for the past 24
hours. Several C-class events were observed throughout the period,
the largest being a C2 flare at 28/1203Z from Region 1199 (N18W48).
Region 1196 (S23W32) regained sunspots and also produced a lower
level C-class event. Regions 1202 (N15W38) and 1203 (N19E77) were
numbered today. Region 1202 emerged as a simple beta group, while
Region 1203 rotated onto the east limb as an alpha group.
IB. Solar Activity Forecast: Solar activity is expected to be at
low levels for the next three days (29 April - 01 May). There also
remains a slight chance for M-class events with Region 1203 rotating
onto the disk and Region 1195 and 1199 continuing to grow and
evolve.
IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z:
The geomagnetic field has been at quiet levels for the past 24 hours.
Measurements by the ACE spacecraft show a solar sector boundary
crossing occurred at 28/1445Z. Solar wind speed increased from
around 320 - 360 km/s, behind a 12 hour bump in density. The Phi
angle also rotated from a positive influence to a negative.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to remain at mostly quiet levels for day 1 (29 April) of
the forecast period. On days 2 and 3 (30 April - 01 May), unsettled
to active levels with isolated periods of minor storming are
expected, due to the arrival of a coronal hole high-speed stream.
III. Event Probabilities 29 Apr-01 May
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF green
IV. Penticton 10.7 cm Flux
Observed 28 Apr 110
Predicted 29 Apr-01 May 110/110/105
90 Day Mean 28 Apr 107
V. Geomagnetic A Indices
Observed Afr/Ap 27 Apr 000/003
Estimated Afr/Ap 28 Apr 001/003
Predicted Afr/Ap 29 Apr-01 May 005/005-010/010-012/012
VI. Geomagnetic Activity Probabilities 29 Apr-01 May
A. Middle Latitudes
Active 10/35/40
Minor storm 01/05/10
Major-severe storm 01/01/01
B. High Latitudes
Active 10/35/40
Minor storm 01/05/15
Major-severe storm 01/01/01
For current space weather conditions please refer to:
NOAA Space Weather Scale descriptions can be found at
www.sec.noaa.gov/NOAAscales
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