Classic Halo CME (May 17, 2005)
Hi-res TIF image (2.9M)
On May 13, 2005 at 17:00 UT a good-sized (M-8) X-ray flare and a CME
(Coronal Mass Ejection) erupted from the Sun from the area of Active
Region 759 (see the large sunspot in the yellow MDI image of the Sun,
upper left). The flare can be seen as a bright, almost white area in
the EIT 195 Angstrom (green) image of the Sun's corona at the left. In the
video one can also see a disturbance spreading out across much of the
Sun from the source of the flare.
Scientists call this phenomenon an "EIT wave". Because the sunspot was just about facing directly towards Earth, the particle cloud of the CME rushed out from the Sun heading right towards us. Its speed was estimated at around 3 million miles per hour. As the CME expanded, it formed a "halo" of bright material around the Sun (therefore the term "halo CME"). This image shows one of the most distinct and well-defined "halo CME's" that SOHO has observed.
The CME cloud reached Earth in about 34 hours and pounded Earth for hours with a powerful solar storm. The SOHO/CELIAS/MTOF particle instrument registered the impact of the CME material as a shock front on May 15. Note the sudden increase in solar wind speed to over 900 km/s and the steep increase in plasma density at around 02:00 UT on May 15. Bright aurora were seen as far south as California and Florida as the charged particles from the storm interacted with and excited atoms in our own atmosphere, causing them to glow in different colors.
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