This shows the X Ray Flux of the September 7th X Class flare. This causes radio blackouts of some bands and is a good indication of immediate earth impact of such an event.
This can be seen also here:
http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap
More info about today's flare:
https://steemit.com/news/@florio/another-x-class-flare-just-erupted-earth-facing
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