STD - CME Impact Prediction *LINK*

[Peter Kuklok]

Event #47 - 26 October 2003
Issued: 06:00 UTC, 27 October 2003

SOURCE EVENT

Class X1.3/3N Flare in Region 486 at 06:54 UTC on 26 October 2003
Type II: 1302 km/sec
Estimated LASCO-derived Plane of Sky Velocity: 1245 km/sec

ESTIMATED TIME OF ARRIVAL OF SHOCK AT EARTH

Estimated Impact Window: 19:00 UTC on 27 October to 12:00 UTC on 28 October
Preferred Predicted Impact Time: 04:00 UTC, 28 October 2003
Estimated Shock Strength (0=Weakest, 9=Strongest): 5

Predicted Behavior of IMF at Shock Impact

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

EVENT #47 NOTES:

Although this event appears to have been associated with a partial halo coronal mass ejection, there is a faint hint in LASCO imagery that perhaps this was close to a halo event. Nevertheless, most of the mass has been ejected east of the Earth. Time of arrival estimates are poor because of the probable interaction of the shock front with a coronal hole stream. Most models we have examined suggest an impact is probable late in the UTC day of 27 October. However, these models do not take into heavy account the observed shape of the CME, which will impact the Earth more obliquely than most models suggest. For this reason, we believe the impact at the Earth will probably occur later than most models suggest - probably in the early part of the UTC day of 28 October. We expect to observe mostly active to periods of possible major geomagnetic storm conditions with this disturbance.
This event does NOT cover the possible effects of the CME associated with the second major X-class flare from Region 484 at 18:19 UTC on 26 October. We are holding off on issuing a prediction for this event due to the SOHO LASCO data outage, which should be corrected within a few hours. Nevertheless, ground-based observations seem to suggest that the CME with this event was directed almost entirely west of the Earth with very little (if any) mass directed Earthward. A better determination will be possible in the next few hours when the data associated with this event becomes available.

[Ulrich Rieth]

Latest Geomagnetic and Auroral Activity Conditions

Updated: 12:50 UTC 27 October (7:50 am EDT, 27 October):

A great deal of activity has occurred during the last 24 hours. There have been 5 major solar flares (6 during the last 36 hours) and at least two known higher velocity coronal mass ejections. The first of these CMEs should impact the Earth within the next 24 hours (see http://www.spacew.com/cme/index.html here for details).

The characteristics of the second CME have not been accurately determined yet, so it is not possible to estimate with any certainty whether there will be an Earthbound impact. Preliminary data indicates most of the mass from the event was directed west of the Earth from solar Region 484, but we are waiting for the SOHO data before making any conclusions.

Solar Activity Update

A major class X1.3/3N solar flare erupted from Region 486 at 06:54 UTC on 26 October. This was followed at 18:19 UTC by another major class X1.2 event from Region 484. This latter event produced a moderately strong space radiation storm (category S2 on a scale of S1 to S5) due to the arrival of enhanced populations of energetic solar protons. A small class M5.0 event was observed in Region 486 at 09:27 UTC on 27 October during a time when x-rays from Region 484 were above M-class levels (this would not have been a major x-ray event had x-rays been riding below M-class levels prior to the lare).
Most recently, a major class M6.7 flare was observed at 12:43 UTC on 27 October. The source of this last event is not yet firmly known.