Solar Flux versus Cosmic Ray Rates as we Approach Solar Minimum

Solar Flux vs Cosmic Rays

We’re keeping an eye on the rate of cosmic ray detection as we approach solar minimum. As the solar flux falls, the strength of the protective bubble of solar wind in our solar system declines. This allows for more cosmic rays to impact Earth. With a weaker solar wind, the strength of our magnetic field also decreases, which exposes us to the effects of solar flares. As the cosmic rays (atomic protons and neutrons travelling at relativistic speeds) interact with our atmosphere, they cause a cascading “shower” of particles to fall to earth, and it’s these events that are detected.

When the solar wind declines, our Earth becomes more exposed to solar CMEs and Gamma Ray Bursts from cosmic events. In extreme cases these events can reach the ground and are detected as “Ground Level Events”. They can cause increased rates of various cancers in humans. People travelling in high altitude aircraft, especially on polar routes, and pregnant women in particular, are at an even higher risk.

Detectors around the world have been monitoring cosmic rays for many decades, and the cosmic ray rate (as of May 2018) is the second highest rate ever recorded. If the current solar minimum deepens further, it’s likely that the previously recorded high (in 2010) will be exceeded.

This site has live links to neutron monitors in Finland. Below is a comparison chart showing the solar flux versus neutron monitor rates from 2000 until May 2018.

Solar Flux (black and left-hand scale – blue line = running average) vs Neutron Count Rate (red with right-hand scale – which is a percentage of the average rate since 2000)

More background information: Space Weather Archive