Joint USAF/NOAA Report of Solar and Geophysical Activity 30 May 2011

:Product: Report of Solar-Geophysical Activity
:Issued: 2011 May 30 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 150 Issued at 2200Z on 30 May 2011
IA. Analysis of Solar Active Regions and Activity from 29/2100Z
to 30/2100Z: Solar activity was low. Five C-class x-ray events were
observed in the past 24 hours. Region 1224 (N20W56) produced a C3
event at 30/0252Z which was accompanied by a faint, but potentially
geoeffective, CME seen in STEREO-B COR2 imagery at 30/1209Z with a
plane-of-sky speed estimate of 610 km/s. Region 1224 grew slightly
and ended the period as a Dso type group with Beta-Gamma magnetic
characteristics. Region 1227 (S18E54) was also associated with CME
activity. At 30/1101Z, this region produced a C2/Sn flare
accompanied by a Type II sweep (1697 km/s) and CME observed in LASCO
C2 imagery (estimated speed 420 km/s). Earlier in the period, Region
1227 produced a C8/Sf that peaked at 29/2120Z. GOES-15 x-ray
signatures indicated this event began at 29/2011Z with northward
surging evident by 29/2035Z. At 29/2124Z, LASCO C2 imagery observed
a potentially geoeffective CME with an estimated plane-of-sky
velocity of 1576 km/s. Associated with this flare were Type II (1548
km/s), Type IV and 10 cm (520 sfu) radio signatures. Region 1227
ended the period as a Dsi type group with Beta-Gamma magnetic
characteristics. Region 1226 (S21E42) produced a C3/Sf flare at
30/0549Z and a C7/Sn flare at 30/0605Z. This region ended the
period as a Dki type group with Beta-Gamma magnetic characteristics.
New Region 1229 (N16E38) was numbered and classified as a Cao type
group with Beta magnetic characteristics.
IB. Solar Activity Forecast: Solar activity is expected to be low
with a chance for M-class events for the next three days (31 May –
02 Jun).
IIA. Geophysical Activity Summary 29/2100Z to 30/2100Z:
The geomagnetic field ranged from quiet to active levels. A coronal
hole high speed stream continued to cause disturbed geomagnetic
conditions. Some signs of weakening were evident at the ACE
spacecraft as solar wind speed decreased from near 700 km/s to about
600 km/s, the total interplanetary magnetic field strength decreased
to less than 5 nT and the average Bz component was approximately 0
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 quiet to unsettled on days 1 and 2 (31 May – 1 Jun)
as the coronal hole high speed stream wanes. Conditions are
expected to remain unsettled with a chance for active periods on day
3 (02 Jun) due to the potential influence from the 29 and 30 May
CMEs.
III. Event Probabilities 31 May-02 Jun
Class M 40/40/40
Class X 05/05/05
Proton 05/05/05
PCAF green
IV. Penticton 10.7 cm Flux
Observed 30 May 112
Predicted 31 May-02 Jun 115/115/115
90 Day Mean 30 May 108
V. Geomagnetic A Indices
Observed Afr/Ap 29 May 017/032
Estimated Afr/Ap 30 May 007/018
Predicted Afr/Ap 31 May-02 Jun 010/015-007/010-010/012
VI. Geomagnetic Activity Probabilities 31 May-02 Jun
A. Middle Latitudes
Active 20/05/10
Minor storm 10/01/05
Major-severe storm 05/01/05
B. High Latitudes
Active 20/05/20
Minor storm 10/01/20
Major-severe storm 05/01/10