The Sun protects us from cosmic rays from beyond the solar system. Every 11 years, the Sun's poles reverse.

Solar cosmic rays are greatest during the reversal.

During the reversal, are we hit by more galactic cosmic rays too? Does the reversal reduce the Sun's protection from them?

Would that harm astronauts heading for Mars at such a time?

  • $\begingroup$ Relevance to space exploration? $\endgroup$ Commented Sep 11, 2020 at 12:32
  • 3
    $\begingroup$ @OrganicMarble The cosmic rays are relevant. They could disturb or even destroy electronics, for example. $\endgroup$
    – Infrisios
    Commented Sep 11, 2020 at 13:32
  • 1
    $\begingroup$ @Infrisios the question needs to show relevance to space exploration to be on topic. Not a comment. $\endgroup$ Commented Sep 11, 2020 at 13:33
  • $\begingroup$ @Infrisios Thankx for the comment. I edited. $\endgroup$ Commented Sep 11, 2020 at 17:25
  • $\begingroup$ The Forbush decrease phenomena is linked to coronal mass ejections, which are more common at solar max, not the reversal direction of the solar magnetic field itself. $\endgroup$ Commented Sep 2, 2021 at 14:45

1 Answer 1


1, Yes, but in an opposite sense.
Cosmic rays are densest when the solar cycle is least active, but that corresponds to when there are the fewest sunspots. But the magnetic field reverses when there are the most sunspots, at "solar max."

2, Yes.
NASA has published extensively about the risks of cosmic rays to astronauts outside Earth's magnetosphere.


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