I would like to compare natural vs artificial (human) emissions in the radio spectrum (f < 1 THz).

The goal is to bring some scientific facts in the debate for deployment of 5G.

It's easy to find info for the spectrum around visible light : enter image description here

I am looking for something similar for radio waves, and ideally some measures of the power of equivalent human emissions (radio, 4G, 5G, etc).

Also, I believe that artificial emissions are usually measured in a different units (V/m) and it's not easy to compare to W/m2/nm.

  • 1
    $\begingroup$ Well, the blackbody equation works well. And human emissions need to be above the noise floor to be useful. $\endgroup$
    – Jon Custer
    Commented Sep 30, 2020 at 12:53
  • $\begingroup$ It depends on whether the sun is active (e.g., solar maximum) vs quiet (e.g., solar minimum). During solar maximum, there are a lot of so called radio bursts which are extremely "radio loud." The sun is loud enough that if a spacecraft passes in between the sun and the Earth, even our most powerful ground-based transponders cannot communicate with it. $\endgroup$ Commented Mar 16, 2021 at 13:32

1 Answer 1


The Sun is incredibly dynamic in the radio frequency range, so there isn't a static value or nice consistent spectrum against which to compare. However, one can show an example figure with ranges of values for reference/comparison. An example is given below from Figure 2 in Cecconi et al. [2017]. Radio sources near Earth

Just to clarify some of the terms in the figure, they are defined as: QTN is quasi-thermal noise, AKR is auroral kilometric radiation (similarly the SKR and UKR are the equivalents for Saturn and Uranus, respectively), SW is solar wind, Solar burst is referring to solar radio bursts (discussed below), and LF cutoff is low frequency cutoff, as you may have guessed.

The largest sources of radio noise from the sun are due to solar radio bursts, which come in at least five major flavors (i.e., named Type I, Type II, Type III, Type IV, and Type V). You can see from the cartoon-like image that the range of flux densities from the sun can be rather large, i.e., upwards of eight orders of magnitude difference between quiet times and peak activity.

From a practical point of view, when viewed from the the first Lagrange point L1, solar radio bursts can be much higher in intensity than any artificial radio source observed from Earth, e.g., see links for the Wind WAVES radio data from https://wind.nasa.gov. Or type "solar radio burst" and look under Images to see numerous examples. The artificial sources will show up as horizontal, narrow bands in the images of frequency versus time spectrograms. Note that Wind has had a rather large diversity in orbital configurations, as discussed in Wilson et al. [2021]


  • Cecconi, B., et al., "NOIRE Study Report: Towards a Low Frequency Radio Interferometer in Space," arXiv 1710.10245, 2017. (Refereed version found at: 10.1109/AERO.2018.8396742)
  • Wilson, L.B., et al., "A Quarter Century of Wind Spacecraft Discoveries," Reviews of Geophysics 59(2), pp. e2020RG000714, doi:10.1029/2020RG000714, 2021.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.