Joint USAF/NOAA Report of Solar and Geophysical Activity 28 May 2011

:Product: Report of Solar-Geophysical Activity
:Issued: 2011 May 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 148 Issued at 2200Z on 28 May 2011
IA. Analysis of Solar Active Regions and Activity from 27/2100Z
to 28/2100Z: Solar activity was low. Region 1226 (S19E65) produced
the majority of the flare activity, including a C8 x-ray event at
28/0331Z. The region grew rapidly in size, spot count and
complexity over the past 24 hours, ending the period as an Eai spot
group with Beta-Gamma magnetic characteristics. Region 1224
(N20W28), a Dso class group with Beta magnetic characteristics, also
grew over the past 24 hours.
IB. Solar Activity Forecast: Solar activity is likely to remain low
for the next three days (29-31 May) with a slight chance for an
M-class event.
IIA. Geophysical Activity Summary 27/2100Z to 28/2100Z:
Geomagnetic field activity ranged from unsettled to major storm
levels over the past 24 hours. The ACE spacecraft observed the Bz
component of the interplanetary magnetic field turned southward
(negative) at approximately 25/0530Z. The field generally ranged
from -5 nT to -12 nT between 27/2130Z to 28/1230Z. The prolonged
southward Bz resulted in substantial geomagnetic disruption and was
attributed to the arrival of a coronal hole high speed stream
possibly coupled with effects from the 25 May filament eruption.
Solar wind speed rose above 500 km/s after 28/0530Z.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to remain at unsettled to active levels, with isolated
minor storm periods, on days 1 and 2 (29-30 May), becoming
predominantly unsettled on day 3 (31 May). This activity is in
response to the continued influence of the coronal hole high speed
stream.
III. Event Probabilities 29 May-31 May
Class M 15/15/15
Class X 01/01/01
Proton 01/01/01
PCAF green
IV. Penticton 10.7 cm Flux
Observed 28 May 101
Predicted 29 May-31 May 100/100/100
90 Day Mean 28 May 108
V. Geomagnetic A Indices
Observed Afr/Ap 27 May 007/011
Estimated Afr/Ap 28 May 032/035
Predicted Afr/Ap 29 May-31 May 020/020-015/015-010/010
VI. Geomagnetic Activity Probabilities 29 May-31 May
A. Middle Latitudes
Active 20/20/15
Minor storm 20/15/05
Major-severe storm 10/05/01
B. High Latitudes
Active 30/30/20
Minor storm 25/20/10
Major-severe storm 15/10/05