Very large x-ray (X17.2) flare from Sunspot Group 070 (NOAA 10486)

The SIDC sent an alert message on October 28 at 12:10 UT:
An X17.2 X-ray flare has just occurred in sunspot group Catania 70 (NOAA 10486) located 20 degrees west of the central meridian. Its peaking time is 11:10 UT (12:10 Belgian time). Coronal dimmings and probably an EIT wave have been observed close to the central meridian in EIT 195 movie, indicating the onset of a coronal mass ejection (CME), which is directed towards the Earth. The CME is first visible in SOHO/LASCO C2 images at 11:06 UT and at 11:42 UT in C3, indicating this is a very fast CME with a speed of the order of 1000 km/s. We therefore expect it to arrive between Wednesday night (29/10) and Thursday night (30/10), triggering a major to severe geomagnetic storm. This could be your chance to see aurorae even in Belgium!

The imagery of the "green" Sun above is taken by the Extreme ultraviolet Imaging Telescope (EIT) on SOHO. The active region which produced the X-flare is bright because it is emitting strongly in 19.5 nm.


The reddish and bluish images show the CME associated with the eruption in white light, resp. in a small and a large field-of-view. The instrument (SOHO/LASCO) that is making these images is called a coronagraph. The dots and stripes are from the impact of high-energy particles slamming unto the camera.

We see an MDI/SOHO image showing the magnetic field strengths: black and white spots denote areas of intense (opposite) magnetic flux. The biggest spot in the middle is the sunspot group that caused the X17.2 flare. It has a size which is 14 times the size of the Earth and is still growing!

The high energy proton fluxes all have exceeded the threshold of 10, indicating the flare was directed to the Earth. This graph is made with data measured by the GOES spacecraft.

Scientists classify solar flares according to their x-ray brightness in the wavelength range 1 to 8 Angstroms. We have the A, B, C, M and X level. X-class flares are big; they are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms. These measurements are made by GOES, a geostationary satellite.

A press release has been sent and is available in Nederlands and Français.



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