Comparison of SID detectors

On 07NOV13 there was a Sudden Ionospheric Disturbance which was captured by three amateur receiving stations:

G4JVF VLF receiving NAA on 24 kHz
W4HBK grabber on 10m receiving G0PKT
W5COV receiving WWVB

This is a comparison of the exact timing of the onset of the SID as seen by the three observers.

G4JVF VLF RX Receiving NAA in Maine

W4HBK 10m Grabber Receiving G0PKT

W5COV VLF RX receiving WWVB in Colorado

I measured the times on the first two by measuring distances with a ruler and interpolating.  Marks estimating the onset were placed first and then the measurements taken.  On the last image since the SID wasn't clear to me I calculated the time estimate from the first two and placed that on the figure.  As I understand it's one of the small spikes.

For comparison here is the X-Ray flux measured by the GOES satellite:

GOES X-Ray Flux for 06NOV13 SID

All things considered the agreement is excellent.  At the time of occurrence the Sun was over the Atlantic which would strongly illuminate the skip points for the EU-US path.   The W5COV-WWVB path was almost in the dark and might be expected to be minimally effected by the SID.

Previously with SIDs I had gotten the impression that the QRSS method was more sensitive to the onset time than were other methods.  But now that I have seen them together and put some numbers with onset features  it looks like there is no significant difference.

de w4hbk