Joint USAF/NOAA Report of Solar and Geophysical Activity 17 May 2012

:Product: Report of Solar-Geophysical Activity
:Issued: 2012 May 17 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 138 Issued at 2200Z on 17 May 2012
IA. Analysis of Solar Active Regions and Activity from 16/2100Z
to 17/2100Z: Solar activity was at high levels due to an M5/1f flare
at 17/0147Z that occurred from Region 1476 (N12W89) as it was
approaching the west limb. Associated with the flare was Type II
(645 km/s) and IV radio sweeps as well as a partial halo CME with an
estimated plane-of-sky speed of approximately 1200 km/s. The
majority of the ejecta was directed off the west limb as seen in
SOHO/LASCO C3 imagery beginning at 17/0206Z, however a shock
enhancement in the interplanetary magnetic field is expected from
the event. Further analysis is pending.
IB. Solar Activity Forecast: Solar activity is expected to be at
predominantly low levels with a slight chance for M-class activity
for all three days of the period (18 – 20 May).
IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z:
The geomagnetic field was at quiet to active levels. An isolated
active period was observed during the 16/2100Z – 2400Z period due to
a prolonged southward period of the Bz component of the
interplanetary magnetic field. A >10 MeV and >100 MeV proton event
at geosynchronous orbit was observed associated with the M5 flare.
The >10 MeV event began at 17/0210Z, crossed the 100 pfu threshold
(S2) at 17/0245Z, reached a max of 255 pfu at 17/0430Z, and fell
below 100 pfu at 17/0945Z. The greater than 100 MeV proton event
began at 17/0200Z and reached a max of 20.4 pfu. Both events were
still in progress at the time of this report.
IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly quiet during the first half of day 1 (18 May).
Around mid to late on day 1, a shock arrival is expected from the
partial halo CME associated with the 17 May M5 flare. Active to
minor storm conditions are expected. Early on day 2 (19 May),
unsettled to active conditions are expected, returning to quiet to
unsettled levels by the end of the day. Quiet to unsettled
conditions are expected on day 3 (20 May).
III. Event Probabilities 18 May-20 May
Class M 20/10/10
Class X 05/01/01
Proton 70/20/05
PCAF yellow
IV. Penticton 10.7 cm Flux
Observed 17 May 136
Predicted 18 May-20 May 135/135/135
90 Day Mean 17 May 115
V. Geomagnetic A Indices
Observed Afr/Ap 16 May 008/009
Estimated Afr/Ap 17 May 006/006
Predicted Afr/Ap 18 May-20 May 011/015-010/008-007/005
VI. Geomagnetic Activity Probabilities 18 May-20 May
A. Middle Latitudes
Active 35/30/10
Minor storm 25/15/05
Major-severe storm 10/05/01
B. High Latitudes
Active 35/35/15
Minor storm 40/25/10
Major-severe storm 15/10/05