Following each flare event, a shockwave of radiation spread out through the solar system, and upon reaching Earth, potent X-rays showered down upon the upper layers of our atmosphere (the ionosphere), causing an event called a sudden ionospheric disturbance, or SID. 

Down on Earth, electronic ears were listening--not to solar X-rays, or even the radio chatter of disturbed atmospheric ions, but rather to human-made radio signals bouncing off of a layer of Earth's ionosphere. 

Around the world, a number of very low frequency (VLF) radio transmitters are stationed to permit communications with submarines and other vehicles.  The signals bounce, or echo, off of a layer of the ionosphere, and back down to Earth where they can be picked up by receivers.  As part of a network of "SID Monitor" stations around the country (and beyond) created and conducted by Stanford Solar Center, Chabot Space & Science Center monitors the VLF transmissions from a station in Washington state, listening for changes in the signal that can be caused by a sudden ionospheric disturbance brought on by a solar flare.

As it turns out, Chabot's SID monitor detected the flare on the 14th, as did many other SID monitoring sites.  The flare of the 13th occurred when it was 6:34 AM Pacific Standard Time--prior to sunrise--and so went undetected here at Chabot.  The flare on the 14th, however, erupted at close to 2:00 PM PST (22:00 GMT).

These two graphs show the detection of the solar flare events.  On the left is the detection by Chabot's SID Monitor on Dec 14.  On the right are the signals from the X-ray detectors on board the GOES 11 and 12 satellites, showing the flares on both dates. 

Chabot Space & Science Center is the Education/Public Outreach site
for the Lockheed-Martin Solar-B SOT/FPP Project