Echoes during CW Sweepstakes

On Saturday night local time I experienced some echoes of my own signal on 80 meters that were pretty interesting. Here are the details:

Timeline

0645Z: I'm bouncing between 40M and 80M following RBN spots.
0648Z: I work 4 stations S&P on 80M, and don't hear any echoes.
0700Z: I pop up to 40M to make a couple of S&P QSOs, then call CQ for a bit with no takers.
0703Z: I drop back down to 80 to call K6JS and hear the echoes for the first time. I can hear them so distinctly in between QSK breaks that I think I'm losing a jump ball (that's when 2 or more stations respond to another station's CQ).



(Direct link to mp3, if your browser isn't showing an audio player.)

0706Z: I find a clear frequency at 3571 and start calling CQ. Again the echoes are so pronounced I think I'm doubling with another station.



(Direct link)

0730Z: I pop back up to 40M for a couple of S&P QSOs. No echo there.

0746Z: I send a series of dits on my CQ frequency so I can measure the delay later using Audacity.



(Direct link)

Here's one echo, zoomed in. I've selected the time period from when I send the dit to when the echo is heard. That's reflected in the "Selection Length" text at the bottom on the window, where you can see that the delay is 0.157 seconds (157 milliseconds). 186,000 mile/sec * 0.157 sec ~= 29,000 miles, roughly the circumference of the earth.

0752Z: I work N6RO and the echoes are starting to fade.

0802Z: I hear K6MMM (about 15 miles directly south of me) and hear echo on Rich/Anna's signal.

0804Z: I head to bed.

What was happening?

I'm not sure if it was related, but there was a coronal mass ejection late last week that impacted the earth. If I recall correctly, the A index was about 42 and the K index was 4 at the time I was hearing the echoes. Those numbers represent geomagnetic activity in the unsettled to minor storm range.

I did find another blog post from W2PA about a similar phenomenon (with links to other QST articles about echoes like this, as well as longer-delayed ehoes). My best guess is this was some sort of magnetospheric ducting. I can't imagine around-the-world multi-hop F2 propagation being this strong. The delay of the echoes is consistent with an around-the-world trip, although from reading the articles, it looks like magnetospheric ducts can take the signal away from the earth and back.

The effect seems to have been localized to stations in the immediate area. One station in Sonoma County (K6SRZ), about 70 miles NNW, reported the effect, as well a few stations just to the south of me in Campbell (W6FB), Cupertino (N3ZZ) and Los Gatos, CA (K6MMM). I did not hear the echoes on stations in SoCal, nor did I see anyone other than N3ZZ reporting it in soapbox comments on the 3830 reflector.

My big regret is that I didn't think to hook up my SDR and capture the entire band data. Then I could have gone back and listened to all the other local stations on 80m to see which ones were experiencing the echo. But what a reminder about how cool mother nature can be!