Does the radiation danger in interplanetary space decrease the further you get from the sun?

Question

Does radiation danger increase or decrease as you travel farther from the Sun?

I understand that there's a significant radiation hazard to astronauts. Say, traveling from Earth to Mars, due to radiation from the Sun and also from other sources.

Does this hazard decrease the farther you get from the Sun and into the outer solar system? I'm not asking solely about the radiation dangers from the Sun. I'm asking about all radiation dangers, regardless of their source. Do levels of any and all radiation sources increase or decrease the farther out you go?

Answer 1

Let's start with a few unspoken assumptions

• Radiation refers to emissions from any body in space. To name a few possible sources
  • Star
  • Nebula
  • Gas giant
• 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.

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Background: 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.

So ...

• 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

1. The risk increases as one moves away from the inner Solar System, and
2. The risk is probably a function of proximity to any alternate sources.

Answer 2

Yes as you move away from our solar system the radiation from the sun decreases because it follows inverse square law.. But other source of radiation is Galactic cosmic radiation :

Galactic Cosmic Radiation (GCR) Galactic cosmic radiation originates outside the solar system. It consists of ionized atoms ranging from a single proton up to an uranium nucleus. The flux (rate of flow) levels are the low. However, since they travel very close to the speed of light, and because some of them are composed of very heavy elements such as iron, they produce intense ionization as they pass through matter.

For the most part, the Earth's magnetic field provides shielding for spacecraft from galactic cosmic radiation. However, cosmic rays have free access over the polar regions where the magnetic field lines are open to interplanetary space.

The flux of galactic cosmic radiation is isotropic outside heliosphere , inside it propagation effect results in an isotropic of approximately 1%

The sun is not only the source of radiation to an spacecraft but there are countless stars like sun in and outside our solar system which emit radiation.

The radiation effects decreases to greater extent ( after heliosphere ) unless the spacecraft is hit by the suddenout burst of galactic cosmic radiation.