22 September 2017 - Mission Day: 7966 - DOY: 265

Another X flare; CME Hits Earth

Click on the images for larger/full field versions.

LASCO C2 Running difference image of halo CME
LASCO C3 Running difference image of halo CME



LASCO C2 image of halo CME
LASCO C3 image of halo CME

1024x1024, MPEGs: 410K, 109K

1024x1024, MPEGs: 482K, 95K

EIT 195 Å MPEGs: 512x512 (450K), 256x256 (157K), 512x512 running difference (588K)
EIT 195 Å subfield MPEGs: 400x400 (265K), 200x200 ( 84K).

Caption: Active region 9415 continues to produce major events. At 05:26 on 10 April 2001, an X2.3 flare went off. A so-called "EIT wave" could be seen in EIT's 195 Å movie. The associated coronal mass ejection (CME) was first spotted by LASCO at 05:30 UT, rapidly developing into a full halo event, heading for Earth, with a plane-of-sky speed estimated at 6 million kilometers per hour. A significant impact is expected when the shock reaches Earth: The shock associated with an M7.9 flare on 9 April 2001 passed SOHO around 13UT, and a second shock at 15:18 UT may have been the one from the X2.3 flare - quite a rapid transit, but not unlikely given the precursor CME arriving just ahead. Both shocks were observed by the SOHO/CELIAS Proton Monitor, as shown below (click for figures including proton density, thermal speed and north/south flow angle).

The geomagnetic effects were quite tangible in Ny Ålesund and Tromsø, Norway, as shown in the magnetogram plots below (click for larger versions. Images courtesy of Tromsø Geophysical Observatory (Nordlysobservatoriet), University of Tromsø Norway). Compass needles were moving about 6 degrees in just minutes as a result of the impact!

The flare was also observed by the TRACE spacecraft. To the left is a 171 Å image of the postflare loops. Click the image for a full-size version. Movies: MPEGs (5.5M, 1.5M), and QuickTime ( 13M


Instruments: Large Angle Spectrometric Coronagraph (LASCO); Extreme ultraviolet Imaging Telescope (EIT);
Taken: 10 April 2001.
Picture credit: SOHO/LASCO and SOHO/EIT (ESA & NASA)


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