A Perfect Storm of Cosmic Rays

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How high will the Earth’s cosmic ray count go this year?

April 23, 2019: Ten years ago, NASA reported a “perfect storm of cosmic rays.” During the year 2009, radiation peppering Earth from deep space reached a 50-year high, registering levels never before seen during the Space Age.

It’s about to happen again.

Ground-based neutron monitors and high-altitude cosmic ray balloons are registering a new increase in cosmic rays. The Oulu neutron monitor in Finland, which has been making measurements since 1964, reports levels in April 2019 only percentage points below the Space Age maximum of 2009:

Source: The Sodankyla Geophysical Observatory in Oulu, Finland.

What’s going on? The answer is “Solar Minimum.” During the low phase of the 11-year solar cycle, the sun’s magnetic field and solar wind weaken. Cosmic rays find it easier to penetrate the inner solar system. In 2009, the sun experienced the deepest solar minimum in a century. Cosmic rays reaching Earth naturally surged.