Joint USAF/NOAA Report of Solar and Geophysical Activity 21 Jan 2005

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2005 Jan 21 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 021 Issued at 2200Z on 21 Jan 2005

IA. Analysis of Solar Active Regions and Activity from 20/2100Z
to 21/2100Z: Solar activity was moderate. There were two M-class
events during the past 24 hours: an M1 from Region 720 (N13W83) at
1016 UTC, and an M1 from Region 719 (S06W90) at 1355 UTC. Two new
regions emerged on the disk today: Region 725 (S04W36) and Region
726 (S02E27).

IB. Solar Activity Forecast: Solar activity is expected to be
moderate. In addition, there is a fair chance for a major flare
and/or proton producing event from Region 720 as it rotates off the
solar disk.

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z:
The geomagnetic field was initially at quiet to unsettled levels
until a sudden impulse occurred at 1711 UTC. The sudden impulse was
preceded by a strong shock at the ACE spacecraft: solar wind
velocity jumped from about 600 km/s to 900-1000 km/s. The sudden
impulse at Earth was followed by magnetopause crossings at
geosynchronous orbit and severe levels of geomagnetic activity. The
shock and subsequent disturbed solar wind were most likely a
response to a CME associated with yesterday’s X7 event. The greater
than 100 MeV proton event that began at 20/0650 UTC continued to
decline during the past 24 hours and dropped below threshold at
21/1845 UTC. The greater than 10 MeV proton event that began 16/0210
continues in progress: flux levels continue to decline with current
levels at about 50 PFU.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be at minor to major storm levels for the next 12-24
hours (22 January) as the current disturbance persists. Conditions
should subside to mostly active levels by day two (23 January).
Unsettled to active levels are expected to prevail on the third day
(24 January) due to effects from a favorably positioned coronal
hole.

III. Event Probabilities 22 Jan-24 Jan

• Class M 90/80/70
• Class X 30/20/10
• Proton 95/50/20
• PCAF in progress

IV. Penticton 10.7 cm Flux

• Observed 21 Jan 114
• Predicted 22 Jan-24 Jan 105/095/090
• 90 Day Mean 21 Jan 108

V. Geomagnetic A Indices

• Observed Afr/Ap 20 Jan 010/012
• Estimated Afr/Ap 21 Jan 045/070
• Predicted Afr/Ap 22 Jan-24 Jan 030/060-020/025-015/015

VI. Geomagnetic Activity Probabilities 22 Jan-24 Jan

A. Middle Latitudes

• Active 30/45/40
• Minor storm 35/25/20
• Major-severe storm 30/05/05

B. High Latitudes

• Active 15/25/35
• Minor storm 25/30/30
• Major-severe storm 55/25/05