Event #79 - 13 December 2006

Issued: 05:55 UTC, 13 December 2006

SOURCE EVENT

X-Class Proton Flare from Region 930 on 13 December 2006
Type II: 1534 km/sec
Estimated LASCO-derived Plane of Sky Velocity: N/A

ESTIMATED TIME OF ARRIVAL OF SHOCK AT EARTH

Estimated Impact Window: 00:00 UTC on 14 December to 21:00 UTC on 14 December
Preferred Predicted Impact Time: 07:00 UTC on 14 December (2:00 am EST on 14 December)
Estimated Shock Strength (0=Weakest, 9=Strongest): 7-8

Predicted Behavior of IMF at Shock Impact

At Shock Impact, the Interplanetary Magnetic Field is predicted to initially turn:
NORTHWARD

EVENT #79 NOTES:

A major class X3.4 solar flare with associated strong radio emissions including a Type II, Type IV sweeps and an intense 44,000 sfu tenflare were observed from Region 930 at 02:41 UTC on 13 December. A prompt Ground Level Event (GLE) was associated with this event as near relativistic protons impacted the Earth's magnetic field. Although there is no LASCO imagery at the time this prediction was released, there is sufficient evidence to suggest that a high velocity coronal mass ejection was associated with this event. The initial impact will likely be associated with a strong northward turning of the Interplanetary Magnetic Field (IMF), which would help reduce the intensity of the geomagnetic and auroral storming that occurs immediately after the disturbance arrives. However, during the following 12 to 18 hours, the IMF is expected to rotate into a southward orientation and produce possibly strong to intense storm conditions. Geomagnetic K-indices of 6 to 9 are considered possible with this event. This is a significant event and has the potential to produce widespread manifestations of geomagnetic and auroral activity during the UTC day of 14 December (evening/early morning hours of 13/14 December over North America).

These predictions may be based on preliminary data and may be revised without warning. The predictions should not be used as a definitive indication of CME impact times or strengths and may frequently be in error. The proprietary methods used to estimate shock impact times are under continual development. Caution is advised.