Let's start with a few unspoken assumptions
- Radiation refers to emissions from any body in space. To name a few possible sources
- Danger means danger to humans
- Sun refers to our very own Sol
The answer may appear to contradict itself at times. This may be because my attempt here is to provide a ... holistic (for want of a better word) view of what little I comprehend, recall, and read.
As already premised, Earth's atmosphere & magnetosphere serve as an umbrella. They shield surface bound Earth life from known sources of radiation. The Sun is perhaps the nearest source of radiation. However even the Solar wind serves to protect planets within the Solar System from Cosmic Rays
Wikipedia writes to say
At distances of ~94 AU from the Sun, the solar wind undergoes a transition, called the termination shock, from supersonic to subsonic speeds. The region between the termination shock and the heliopause acts as a barrier to cosmic rays, decreasing the flux at lower energies (≤ 1 GeV) by about 90%. However, the strength of the solar wind is not constant, and hence it has been observed that cosmic ray flux is correlated with solar activity.
An independent source for the above
Moving onwards - another major source of radiation within the Solar System is Sol itself. The planetary fact sheets available from NSSDC show Solar irradiance fall as one moves within the Solar System from Mercury to Pluto. Of course, this is inclusive of the visible spectrum.
- Cosmic ray radiation within the Solar System is affected by Sol's weather.
- Incident radiation from Sol is directly proportional to distance from the Sun
Still staying within the Solar System, what are the other possible sources of radiation? DeerHunter's comment of Aug 22 provides an answer. The Gas giants are audible in the radio bands; they may be a source, and therefore potentially dangerous. A person standing within a pressure vessel of a reactor would likely be in danger regardless of Cosmic Rays, and Solar radiation; replace 'reactor' with, say, Jupiter and the analogy fits to a 'T'.
Between the known major sources (Cosmic Rays, and Sol) my impressions are
- The risk increases as one moves away from the inner Solar System, and
- The risk is probably a function of proximity to any alternate sources.