Comment added at 05:33 UT on April 10: Region 9415 (image at the time of the flare) is the source of a major X2.2 flare currently in progress. It is likely that the flare has produced a major geoeffective CME which could reach Earth already by noon tomorrow April 11. Further details will be posted within a few hours. (What effect does such a large flare have on the radio spectrum? See image from the Learmonth observatory.)

Comment added at 07:48 UT: The above X2 flare was associated with a strong type II sweep with an estimated shock speed of 2100 km/sec (+/- 250 km/sec). The CME should impact Earth tomorrow and could arrive soon after midnight causing solar wind speeds near Earth to reach 1000 km/sec or more. A severe or very severe geomagnetic storm is expected with planetary K indices in the 6-9 range. The flare itself may have been triggered by a filament eruption inside region 9415, this event began less than one hour prior to the flare. No significant increase in energetic particles have been observed near Earth yet, however, the above 10 MeV proton flux could reach event level soon.

Comment added at 11:41 UT: The above 10 MeV proton flux is increasing steadily and has so far reached the 40 pfu level. The X2 flare this morning disrupted filaments 40-50 degrees away from the center of the eruption, this degree of disruptive effect is highly unusual. The most interesting question now is how strong tomorrow's geomagnetic storm will become. Potentially it could become an extreme storm (G5). Image of the monster CME in LASCO C3

-- Anonymous, April 10, 2001

Answers

Bummer, any chance at a decent light show is a guarantee of heavy overcast in these parts.

-- Anonymous, April 10, 2001

NC is not sending snow to you this time, though. However, Tstorms rains may be a problem later in the week. Better see if David can dance a preemptive strike.

-- Anonymous, April 10, 2001

Comment added at 18:19 UT on April 11: Two solar wind shocks have been observed today. The first was a moderate shock and was recorded at SOHO at 13:02 UT with solar wind speed increasing suddenly from 500 to 620 km/sec. The source of this shock was likely a halo CME observed on April 9. A much more significant shock was observed at SOHO at 15:18 UT, this time with solar wind speed increasing from 630 to 860 km/sec over a short time span. The source of this disturbance was the large halo CME observed on April 10. Magnetometers at all latitudes displayed strong fluctuations when the CME reached Earth at 16h UT, several recorded a K index of 8 (very severe storm) or 9 (extreme storm) during the first hour of the disturbance. If the disturbance continues at its current intensity it could be possible to observe aurora in southern Europe and most of North America. The planetary A index for the 15-18h UT interval was 200.

-- Anonymous, April 11, 2001