Joint USAF/NOAA Report of Solar and Geophysical Activity 16 May 2005

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.
Updated 2005 May 16 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 136 Issued at 2200Z on 16 May 2005

IA. Analysis of Solar Active Regions and Activity from 15/2100Z
to 16/2100Z: Solar activity was moderate. Region 763 (S16E04)
produced three low level M-class flares. The largest of these
flares was a M3.5 at 15/2236 UTC. This region has increased in size
and complexity and now exhibits a beta-gamma magnetic
classification. Beginning at 16/1350 UTC, LASCO imagery showed what
appeared to be a partial halo CME. This event was actually two
events. The first was a DSF near Region 759 (N11W35) at
approximately 16/1243 UTC and the second was a backside event at
approximately 16/1358 UTC. Most of the front side ejection was
directed northward; therefore, the event is not likely to be
geoeffective.

IB. Solar Activity Forecast: Solar activity is expected to be low
to moderate.

IIA. Geophysical Activity Summary 15/2100Z to 16/2100Z:
The geomagnetic field was at quiet to minor storm levels with a
period of major storm conditions between 16/0300 UTC and 0600 UTC.
Solar wind speed at ACE has been steadily decreasing from
approximately 800 km/s to 550 km/s by the end of the period. The Bz
component of the IMF has remained south between -1 nT and -10 nT
during this reporting period. The greater than 2 MeV electron flux
at geosynchronous orbit was high today.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be unsettled to active with an isolated minor storm
period possible on 17 May due to a recurrent coronal hole high speed
stream becoming geoeffective. Quiet to unsettled conditions are
expected on 18 and 19 May.

III. Event Probabilities 17 May-19 May

• Class M 50/50/50
• Class X 10/10/10
• Proton 10/10/10
• PCAF yellow

IV. Penticton 10.7 cm Flux

• Observed 16 May 099
• Predicted 17 May-19 May 100/100/095
• 90 Day Mean 16 May 092

V. Geomagnetic A Indices

• Observed Afr/Ap 15 May 044/105
• Estimated Afr/Ap 16 May 020/030
• Predicted Afr/Ap 17 May-19 May 012/020-008/012-005/010

VI. Geomagnetic Activity Probabilities 17 May-19 May

A. Middle Latitudes

• Active 25/20/15
• Minor storm 10/10/05
• Major-severe storm 01/01/01

B. High Latitudes

• Active 30/25/20
• Minor storm 25/10/10
• Major-severe storm 15/01/01