| Space weather is a complicated subject. Solar flares emit both photons and protons. The photons are part of the electromagnetic radiation which reaches earth at the speed of light. The protons ejected with or by the flare are mass at very high speeds and can reach earth in as little as 30 minutes. Flares are often accompanied by CME’s which, as the name suggests, are mass ejections and reaches earth typically in a day or two. Solar storms are the high speed protons. CME’s also disrupt radio.
There is enough information on space weather online to make almost anyone’s eyes glaze over if you want more. - David WJ9O On Jan 5, 2024, at 11:15 AM, Mike Knerr via BVARC <bvarc@bvarc.org> wrote:
I understood that a coronal mass ejection released protons, not photons. These also bring high electromagnetic fields with them. I understood the electromagnetic fields are causing the problems. Just a thought. Mike Knerr KI5UBL 73 On Fri, Jan 5, 2024, 10:03 AM Stephen Flowers via BVARC < bvarc@bvarc.org> wrote: Richard, Good morning and Good question. The way I understand it, solar flares emit a large amount of photons at various frequencies. If these photons are sufficiently energetic, then they will pass a large portion of the ionosphere and impact what we refer to as the D layer. Note that the D layer is a daytime ionospheric layer that according to some models in the literature is made up of NO+, NO+(H2O)n, H+(H2O)n, CO3−, and O3−
These species readily combine with free electrons that increase in numbers due to the flares. This in turn results in “less refraction" of E&M waves that we as amateurs need to bounce our signals off of to communicate. In a nutshell, D layer constituents don’t refract as much and this is interpreted as “D layer absorption”. If you look at this URL you can playback a movie of the latest D layer absorption measurements. During a solar storm you’ll see the bar graph in the right hand corner increases across multiple frequencies.
Note that in a solar flare event the lower frequencies are preferentially impacted.
Of course other layers in the ionosphere are also affected by solar flares in ˜8 minutes of emission and CMEs hit us w/a delayed impact of ˜1 day or so; however, you may be on to something when you say that the lower frequencies suffer a bigger impact. In that case, you may be right in that the higher frequencies, 20m and higher, may be the way to go for Ham radio ops during solar storms.
Thank you for bringing up this topic!
73, Stephen (W2WF)
On Jan 5, 2024, at 9:03 AM, David Holden via BVARC < bvarc@bvarc.org> wrote:
A strong solar storm can cause a complete blackout of HF communication including the higher frequency bands. I was in a QSO a year or so ago and it just dropped as a solar storm hit. The noise floor dropped to zero as not even noise could propagate through the highly energized atmosphere. Lesser solar storms can increase noise particularly on the lower bands so 80 might be unusable while 20 might just be noisy. David WJ9O On Jan 4, 2024, at 10:25 PM, Richard Bonica via BVARC <bvarc@bvarc.org> wrote:
To all,
Tell me if I am wrong on this. During these solar storms, it is my understanding to use the higher frequency rather than lower? If so, is 20 and 40m bands a good choice?
Thank you in advance
Richard
KG5YCU
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