That particular trace was at 24KHz--looking at the NAA station in Cutler, Maine.Marcus, this is amazing data. What frequencies are in your VLF band?
Pace
Here is the data for NML, at 25.2Khz, located in LaMour, North Dakota:
You can see that the response is absorptive, rather than reflective, and less intense, along this very-much-longer path between
my receiver and the transmitter in North Dakota. In particular, the M7 at 15:20 UTC isn't even visible in this data, because the Sun
angle at the transmitter site was probably "all wrong" to get a strong response at that time of day.
I monitor several different frequencies, and submit data to the Stanford SID data center every day. With my 96KHz sound card, and loop
antenna, I can "see" from a few hundred Hz to around 45KHz or so.
-- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org