Strange afternoon MW DX flare (5,500 and 7,500km!)
Posted: Sat Nov 05, 2022 10:25 am
Friday afternoon (November 4th) around 14:20 UTC (15:20 local) I was scanning the MW band with my indoor YouLoop, when I heard an unusual Russian speaking station on an unusual frequency of 1521 kHz getting stronger and stronger. MWList.org had nothing Russian in the Europe/Africa/Middle East list for that frequency... that was because the station wasn't in that part of the world: It was "Radio Kitaya" a Russian program from CRI transmitted from Hutubi in northwestern China with a whopping 500kW:
However, it was still broad daylight and that station is just as whopping 5,445km or 3,383 miles from here, that's roughly the distance between Anchorage, AK and New York City, and the signal was unusually strong even for that kind of power (10dB less = 50kW would've been no problem). The band was otherwise still very much in daytime mode, like 2 hours before sunset!
Of course I scanned the band more while it lasted and heard a few more Chinese language stations, one of them was taking out BBC Aberdeen on 1449 kHz. The spectacle lasted for maybe 30 minutes with fading intervals of ~5 minutes, then the stations disappeared again (and Radio Kitaya flared up once again hours later after sunset). When I conversed about it with Thomas later that evening I remembered that I forgot looking up where the 2 possible Chinese 10kW transmitters on 1449 kHz are located and found out that both are in eastern China, one 7,425km/4,613mi away and the other 7,820km/4,860mi and I Instantly regretted not having recorded that one... what the Heaviside?
My basic theory is that the signal was refracted on the dark side of the grayline and slipped underneath the likely still heavily charged D-layer (HSS influence) to its destination, my indoor YouLoop.*
That doesn't explain the signal strength from that kind of distance and how that short and (at least to me) pretty out of the ordinary flare-up was over so quickly? I checked the realtime solar data off the NOAA page and noticed the event coincided at most with changes in the interplanetary magnetic field strength components Bz/By/Bx and Phi (angle) of the field. Other parameters I could find (without knowing what I'm even looking for) did not give away any indication of how space weather could've had a word in this.
Whatever it was, it was unexpected and reminded me how little I understand the role of space weather in MW DX. However, another part of my ad-hoc theory is that this was a rare (?) occurrence of an extended (more than 4,000km) one-hop propagation path. I think this could only work this good for eastbound paths because the refraction would happen in a still nicely charged F2-layer since the sun went away only a short time before. For westbound paths, the refraction point would be either in the F-layer of the dark side already having lost much of its ionization over night, or a freshly charged F-layer on the day side but then the D-layer would be in the way, particularly with conditions like this (high A-index).
Apparently, even the old MW is always good for a surprise! Has anyone ever witnessed something like this?
However, it was still broad daylight and that station is just as whopping 5,445km or 3,383 miles from here, that's roughly the distance between Anchorage, AK and New York City, and the signal was unusually strong even for that kind of power (10dB less = 50kW would've been no problem). The band was otherwise still very much in daytime mode, like 2 hours before sunset!
Of course I scanned the band more while it lasted and heard a few more Chinese language stations, one of them was taking out BBC Aberdeen on 1449 kHz. The spectacle lasted for maybe 30 minutes with fading intervals of ~5 minutes, then the stations disappeared again (and Radio Kitaya flared up once again hours later after sunset). When I conversed about it with Thomas later that evening I remembered that I forgot looking up where the 2 possible Chinese 10kW transmitters on 1449 kHz are located and found out that both are in eastern China, one 7,425km/4,613mi away and the other 7,820km/4,860mi and I Instantly regretted not having recorded that one... what the Heaviside?
My basic theory is that the signal was refracted on the dark side of the grayline and slipped underneath the likely still heavily charged D-layer (HSS influence) to its destination, my indoor YouLoop.*
That doesn't explain the signal strength from that kind of distance and how that short and (at least to me) pretty out of the ordinary flare-up was over so quickly? I checked the realtime solar data off the NOAA page and noticed the event coincided at most with changes in the interplanetary magnetic field strength components Bz/By/Bx and Phi (angle) of the field. Other parameters I could find (without knowing what I'm even looking for) did not give away any indication of how space weather could've had a word in this.
Whatever it was, it was unexpected and reminded me how little I understand the role of space weather in MW DX. However, another part of my ad-hoc theory is that this was a rare (?) occurrence of an extended (more than 4,000km) one-hop propagation path. I think this could only work this good for eastbound paths because the refraction would happen in a still nicely charged F2-layer since the sun went away only a short time before. For westbound paths, the refraction point would be either in the F-layer of the dark side already having lost much of its ionization over night, or a freshly charged F-layer on the day side but then the D-layer would be in the way, particularly with conditions like this (high A-index).
Apparently, even the old MW is always good for a surprise! Has anyone ever witnessed something like this?