Is Solar Radio Flux dependent on Spectral Class?

[yannick7]

TL;DR Summary: Is Radio Flux dependent on Spectral Class? If yes, which Spectral Classes have the highest Radio Fluxes?

Is radio flux dependent on spectral class? If yes, which spectral classes have the highest radio fluxes?
I am currently working on a presentation about astrophysics and planet habitability. I found a list of the 10 exoplanets that have the highest chance of being habitable. One of the columns describes the solar radio flux. Well, I want to describe every column and be able to give my classmates some understanding about what every column means and how exoplanets get classified in terms of habitability.

 

[berkeman]

Welcome to PF.

What have you found so far in your research? Can you link to some of the reading that you've been doing about this question? Thanks.

 

[yannick7]

Hello

thank you for your quick response :D

So, it's a chosen topic and the presentation is ungraded. After some communication with the teacher, we were also told, that we can use Wikipedia for our chosen topics.
So far I read the german Wikipedia article about solar radio flux, the english version of it, this article of 'noaa' and some more. Well, after some more thinking, I can also maybe reformulate my question a little bit: Does the spectral class have influence on the solar activity (and with that on solar radio flux of a planter), if yes, which spectral classes have an enough high energy to make a solar system inside the typical habitability zone inhabitable? (So, it's my conclusion that it can make a planet inhabitable, because it's mentioned in the table, I talked about. Linked is the english version, I will use the german version for my presentation.)

 

[Bystander]

which spectral classes have an enough high energy to make a solar system inside the typical habitability zone inhabitable?

"Habitable?" Or, Un/not "habitable?" The language, English, is very unsuitable for this question, "Is life possible, or not."

 

[Bandersnatch]

The German article links to a different page for the column description than the English one, where it's linked to radiant flux, not radio flux.
In the context of the table, it would only make sense for it to be the stellar flux received at the orbital distance from the star (so more like radiant than radio flux). It's just how much stellar energy is present in the planet's neighbourhood relative to what the Earth gets.

The table on Wikipedia, however, is suspect, in that it has entries with higher flux and lower effective temperature. This is unphysical, as this should follow from the black body radiation that more flux equals higher effective temperature (depending on the level of the presentation, the calculation might be useful to show). It's possible some entries use effective temperature above the atmosphere, and some use the surface temp assuming certain atmospheric composition. Hard to tell where the discrepancies come from without tracking each source individually.

It's a common issue on the Wiki where different sources are often supplied for different values, without much regard for how they're calibrated or how they fit together - which is why you should always pick a more curated source for more serious purposes.
If you look at the table(s) below:
https://phl.upr.edu/projects/habitable-exoplanets-catalog
from the Arecibo's Planetary Habitability Laboratory at UPR, the entries are more consistent. You'll see that it's at least in some sections (e.g. the definitions in the German article) it's what formed the basis for the Wiki articles.

Radio flux itself is unlikely to be of issue for habitability. It's true that main sequence stars lower on the H-R diagram have higher relative radio flux. The lower the black body temperature, the more shifted the spectrum towards the longer wavelengths is. But it's the shorter wavelengths that you should be worried about with regard to atmospheric stripping or biological sterilisation.

Having said that, I've seen papers discussing the high propensity of low-mass stars for flaring - which spikes high-frequency emissions - and how it may or may not affect habitability (I've seen both for and against arguments). I don't have the literature wherewithal to tell you what's the consensus on that, though. You may want to do a deep dive e.g. on arxiv, if you care and have some intuitions on how to judge papers. Or just mention it in passing. Or not at all.

Another thing you might want to include is how the basic black body radiation or standard Earth-like atmosphere pictures can be altered by differing planetary atmospheres. Kopparapu et al. 2013 may or may not be over your head (we don't know your background) but in any case it does include a nice interactive calculator for how habitable zones are affected by different strengths of greenhouse effects. You'll find the link to the calc in the paper (to be found on arxiv or elsewhere).

 

[yannick7]

Hello Bandersnatch,
Thank you very much for your really useful and still well understandable answer. I wasn't aware of the difference of the German and English Wikipedia...

This will help much creating this presentation and explain the topics to complete newbies to the topic. (At least I got a maximum of 45 minutes for the whole presentation, so I should have more than enough time to explain everything in detail.)

Thanks for taking your time and have a great day :D

 

[davenn]

Is radio flux dependent on spectral class?

No, it isnt, you have read a number of articles
Surely one of them told you where (what frequency) that the daily radio flux is taken at ?

Now that is the standard radio solar flux that is spoken of when referring
to solar activity.
That doesn't negate the fact that "a flux" can be taken at any frequency.
It's just not what is done for normal use.

The table on Wikipedia, however, is suspect, in that it has entries with higher flux and lower effective temperature.

The higher radio solar flux is related to a cooler sun.
This is because higher flux = more sunspots and they are cooler ( around 1000C) than
the surrounding solar photosphere and therefore a lower overall temperature
from the photosphere.

Dave