Odd behavior on 80 post X-class flare (red lines are the begining and end of flare):

[Vincent Leveque]

I'm looking at the impact of an x-class flare on March 30 2022 on HF propagation, using WSPR observations.

7 Mhz (40 meters) looks as expects - a sudden decline in SNR at the time of the flare followed by a gradual recovery.  On 80 meters, I notice an increase in SNR lasting about 2 hours, with no dropoff.

Is a solar flare somehow enhancing 80 meter propagation?  Is is causing a decline in noise which more than compensates for the drop in signal?

I've looked at 80 meters for the preceding day as a control and see no SNR change

[Jonathan]

Vincent,

Just for reference, I was able to detect this flare on the VLF transmitter NAA at 24 kHz:

Ignore the bottom plot as that data is invalid, but the top plot is the amplitude of the signal showing an enhancement during the time of the flare. 

Your observation is indeed odd. I wonder what other HF observations show. At VLF, sometimes there is an "inverted shark fin" response showing a diminishing of propagation during a flare, which is the opposite of the typical response. I wonder if this phenomena can occur at HF but show an enhancement like you are observing.

Jonathan

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[Bob Gerzoff]

Intriguing. This is counterintuitive to me. I assume the times are GMT? This would be early evening local time, right? It is undoubtedly not explainable with what would happen with D-layer absorption. I don't think so anyway. I wonder if it has something to do with gray line propagation?

 

Try posting to the HamSci group. If we don't get an explanation, it should engender some interesting conversation at least.

 

From: ham...@googlegroups.com <ham...@googlegroups.com> On Behalf Of Vincent Leveque
Sent: Wednesday, June 05, 2024 10:57 PM
To: HamSCI <ham...@googlegroups.com>
Subject: [HamSCI] Odd behavior on 80 post X-class flare (red lines are the begining and end of flare):

 

I'm looking at the impact of an x-class flare on March 30 2022 on HF propagation, using WSPR observations.

 

7 Mhz (40 meters) looks as expects - a sudden decline in SNR at the time of the flare followed by a gradual recovery.  On 80 meters, I notice an increase in SNR lasting about 2 hours, with no dropoff.

 

Is a solar flare somehow enhancing 80 meter propagation?  Is is causing a decline in noise which more than compensates for the drop in signal?

 

I've looked at 80 meters for the preceding day as a control and see no SNR change

 

 

 

 

 

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