On a number of occasions I have commented about southern-originating signals that struggle to move north during periods of elevated geomagnetic activity. I get a lot of blank stares when I say this as it is obviously not clear what I mean. Last night, only a few hours after full dark here in North Texas, I observed a textbook example using WSPR.
Just prior to the above screen shot being taken, my signal was being reported in the north east. This was around 0230z. The geomagnetic field took a hit around 0300z which led to a K index increase to 6. The screen shot reflects that period after the K index spiked to 6. The recovery was fairly quick but the S/N struggled to return to the pre-GMF disturbance levels. Note the lateral distribution of my signal. Its no longer being reported by the northern stations.
The VHF and UHF guys are successful at using these solar disturbances to their advantage. The signals are able to propagate successfully to the region of intense ionization and reflect and refract like a light shining on a mirror. But why might a signal at 630-meters not be able to move north into those regions of ionization? Intense absorption of the sky wave signal might be one good reason but reduced signal levels have been observed on ground wave signals while moving north as well during daylight hours. This really should not be happening yet it does.
The answer may lie in the Planck-Einstein relationship that says,
E = Energy in Joules
h = Planck’s constant in Joule-seconds, 6.62606957×10−34
ν = frequency in Hertz
The general relationship indicates that as frequency increases, energy increases in accordance with Planck’s constant. We might not often think of energy differences in our RF signals based on frequency but, in fact, signals at 475 kHz are almost three orders of magnitude less energetic than signals at 144 MHz. Its no wonder that our signals at these low frequencies struggle so much against these magnetic disturbances and are often pushed further south. This fact might be advantageous on the transequitorial path and will have to be examined further as we go forward.
There are some interesting observations of signals moving from North to South under disturbed conditions as well but I will save those discussions for another time when I have ample visual aides.