Propagation Related Data

[KW2P]

It just occurred to me that I find myself constantly flipping back and forth between SpaceWeatherLive and any site that displays the data on this banner:

http://www.hamqsl.com/solar.html

Items of greatest interest are:

Solar Flux Index
Sunspot Number
Kp Index
X-Ray Flux
304 Angstrom Flux
Solar Wind Speed

A couple of the above are shown on SpaceWeatherLive but not all of them.  Or maybe I haven't found them.  Lol.

[Marcel de Bont]

We have all those items but what is the 304 Angstrom Flux you are talking about? That doesn't ring a bell

[KW2P]

1 minute ago, Marcel de Bont said:

We have all those items but what is the 304 Angstrom Flux you are talking about? That doesn't ring a bell

My understanding is it's the intensity of UV radiation at 304 Angstroms, which I believe is the most important wavelength for ionizing the F1 and F2 layers of the ionosphere that radio depends on.

Radio people like me wish for high levels of 304A and x-rays, and a low Kp index. This results in the best radio conditions. Coincidentally, conditions right now are the best I've seen in a long while because we have all of the above.

[KW2P]

I've been looking around the site at things I don't normally look at. I see plenty of great imagery at 304 Angstroms but not a total flux value.  In other words, the overall brightness of the sun at 304A.

I've never looked to see what in the ionosphere is absorbing the 304A UV -- oxygen, nitrogen, what?  I'll have to see if I can find the answer.

[FairyG]

1 hour ago, KW2P said:

I've never looked to see what in the ionosphere is absorbing the 304A UV -- oxygen, nitrogen, what?  I'll have to see if I can find the answer.

If you can let me know when you find out, I'd appreciate it!

[Marcel de Bont]

10 uren geleden, KW2P zei:

I've been looking around the site at things I don't normally look at. I see plenty of great imagery at 304 Angstroms but not a total flux value.  In other words, the overall brightness of the sun at 304A.

I've never looked to see what in the ionosphere is absorbing the 304A UV -- oxygen, nitrogen, what?  I'll have to see if I can find the answer.

I am not familiar with this at all? Is this a value that SDO can measures or something with the AIA 304 channel?

[KW2P]

Hmm.  Good question. I'll see if I can find out where that number comes from.

I did some research last night and gathered some documents I need to print and read. I did learn that 60 percent of the ionization that matters for radio propagation comes from UV in the range of 26 to 32 nm.  So that's why that 304A number correlates with improved propagation. I presume that X-rays account for the rest of the ionization but am not sure. (yet)

There's also a time factor. The radiation doesn't result in an immediate improvement, it builds up over a few hours. When the radiation drops or it's night, the ionation remains and fades slowly.  At solar max, there's so much ionization that radio propagation is excellent 24 hours a day on bands as high as 10 meters (30 MHz). During really strong cycles like the Modern Maximum in the 1950s, even the 6 meter VHF band (50 MHz) opens worldwide 24 hours. During the Modern Max, 56 MHz television signals were being picked up across the Atlantic Ocean.  (6 meters is normally a local band, useful for line-of-sight communications only so you can see how crazy this is and why it's so exciting for radio amateurs.)

Anyway, I'll see what I can find.

11 hours ago, FairyG said:

If you can let me know when you find out, I'd appreciate it!

Will do.  Now that I'm on this topic, I intend to pursue it all the way.  I've used these numbers for decades to forecast radio propagation but never dug down for details.

[Drax Spacex]

Some interesting insights about 304A from this web page:

http://www.bidstrup.com/w7ri-hf-radio-propagation.htm

" The 304A Index is the relative strength of total solar ultraviolet radiation at a wavelength of 304 angstroms, emitted primarily by ionized helium in the sun's photosphere. There are two running indexes available for this parameter, one measured by the new Solar Dynamics Observatory, using the EVE instrument, and the other, using data from the older SOHO satellite, using its SEM instrument. This one is from the SOHO's SEM instrument, and the index number here is roughly equal to the index on the plot to the right, which also comes from SOHO's SEM instrument. While the SDO satellite is more sensitive to change, and is a newer instrument, the older SOHO index is more widely watched simply for historical reasons, and so it is the one used here. The background level - at solar minimums - will typically be around 134, and at solar maxima can exceed 200 or more.

It is solar radiation in this frequency band that is directly responsible for about half of all the ionization of the F2 layer, the ionosphere layer of greatest significance to us (the other half is due to solar wind electrons and protons, and the soft X-ray radiation (upper red graph to the right) together in about equal measure. The solar wind electron inflow is how F2 propagation can remain open at night). Watching this number and observing the trend along with the X-ray flux number in the plot to the right will tell you whether the upper frequency band conditions - mostly 30m through 10m - will be improving or degrading over the next few hours. If a time is given, it is the time (in GMT) at which the measurement was made - this index is updated frequently because such things as solar flares and coronal mass ejections can affect the number dramatically over short periods. This is a better index to watch, especially at high sunspot numbers, than the older Solar Flux Index everyone has grown accustomed to watching. That is because the old SFI (which measures solar microwave radiation at 2800 Mhz.) was used for many years to serve as a proxy for this parameter, because in the old days before satellites it was not possible to observe this wavelength directly from the surface of the earth. The problem with watching SFI is that the correlation between it and the 304a radiation falls apart at SFI numbers above about 110. "

[KW2P]

Well, there's the answer right there. I haven't had time to do more digging than I did last night and was hoping to get to it later tonight. Thank you!

[Marcel de Bont]

Very interesting thanks. Wonder if there is a data feed somewhere for these numbers.

[Drax Spacex]

I found this EVE site which provides irradiance in mW/m² for various wavelengths, including 30.4nm.  I haven't found a feed for or formula/algorithm for the 304A Index.  https://lasp.colorado.edu/eve/data_access/eve-space-weather/index.html

[KW2P]

22 minutes ago, Drax Spacex said:

I found this EVE site which provides irradiance in mW/m² for various wavelengths, including 30.4nm.  I haven't found a feed for or formula/algorithm for the 304A Index.  https://lasp.colorado.edu/eve/data_access/eve-space-weather/index.html

Wow, this is great stuff. I'm collecting links at the moment because I'm working.

I too am interested in finding raw data feeds. With that I can create hidden pages on one of my web sites that aggregate the data and present it for personal use.

[KW2P]

On 3/29/2022 at 3:55 AM, FairyG said:

If you can let me know when you find out, I'd appreciate it!

I found out. The answer is nearly all of the EUV (wavelengths shorter than 1000A) is absorbed by oxygen, O2 and O3, which become ionized.  This results in oxygen ions and free electrons which reflect electromagnetic radiation (radio waves) longer than a certain wavelength that depends on the intensity of the ionization and the angle at which the the radio waves strike the ionized layer. The more oblique the angle, the stronger the reflection (which I knew).

An interesting thing I learned was why there's such a focus on loss of ozone due to CFCs. Ozone (O3) has an inordinately large equivalent cross-sectional area when it comes to absorption of dangerous EUV, far larger than O2. While the majority of EUV is absorbed by O2 because it's far more abundant than O3, it's the O3 that guarantees that none of the EUV reaches the ground.