Proton events on east limb extremely rare

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.
Updated 2005 Sep 08 2204 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 251 Issued at 2200Z on 08 Sep 2005

IA. Analysis of Solar Active Regions and Activity from 07/2100Z
to 08/2100Z: Solar activity remains at high levels. An X5/2b flare
was in progress from Region 808 (S09E67) at the time of this
writing. Moderate centimetric radio bursts are also in progress,
including a 990 sfu Tenflare. Very active Region 808 is rotating
into view as a large and complex sunspot cluster. Limb proximity is
still hindering the analysis, but this compact spot group will
likely exceed 1000 millionths of white light area. Numerous C-class
flares and two M2 flares preceded the X5 event. New Region 809
(N10E60) was numbered today.

IB. Solar Activity Forecast: Solar activity is expected to remain
at high levels. Region 808 is a large and complex sunspot group
capable of producing M and X-class flares.

IIA. Geophysical Activity Summary 07/2100Z to 08/2100Z:
The geomagnetic field was quiet to unsettled. A sudden disturbance of
41 nT (magnetic crochet) was observed in the geomagnetic field
following today´s X5 flare. A greater than 10 and greater than 100
MeV proton event occurred following yesterday´s X17 flare on the
southeast limb. The greater than 10 MeV proton event began at
08/0215Z and remains in progress. The peak flux so far was 87 pfu at
08/1950Z. The greater than 100 MeV proton event began at 08/0405Z
and also remains in progress. The peak flux was 7 pfu at 08/1925Z.
............A greater than 100 MeV proton event from a source on the east
limb is extremely rare.................. The greater than 2 MeV electron flux at
geosynchronous orbit was at high levels again today.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to range from quiet to minor storm levels. The CME
associated with yesterday´s X17 flare was very large and very fast.
Although the magnetic cloud associated with this CME is not expected
to impact Earth, a shock passage is expected, which will likely
produce active to minor storm periods on 09 Sep. Isolated active
periods are expected on 10 and 11 Sep. The greater than 10 MeV
proton event currently in progress is expected to continue through
10 Sep. A further enhancement in the greater than 10 MeV protons
will likely follow the anticipated shock passage on 09 Sep. Today´s
X5 flare may enhance the existing proton event. The greater than 100
MeV proton event will persist through 09 Sep.

III. Event Probabilities 09 Sep-11 Sep
Class M 80/80/80
Class X 50/50/50
Proton 99/90/75
PCAF in progress

IV. Penticton 10.7 cm Flux
Observed 08 Sep 094
Predicted 09 Sep-11 Sep 100/110/110
90 Day Mean 08 Sep 091

V. Geomagnetic A Indices
Observed Afr/Ap 07 Sep 018/015
Estimated Afr/Ap 08 Sep 008/012
Predicted Afr/Ap 09 Sep-11 Sep 020/025-015/020-008/010

VI. Geomagnetic Activity Probabilities 09 Sep-11 Sep
A. Middle Latitudes
Active 40/30/25
Minor storm 20/15/10
Major-severe storm 10/05/01
B. High Latitudes
Active 50/40/30
Minor storm 30/20/15
Major-severe storm 15/10/05