Weak Solar Cycle: Cosmic rays increase 4th year in a row

Increased exposure for airline travelers at high altitudes.

New data released by the Earth to Sky Calculus/Spaceweather.com high-altitude ballooning program show that atmospheric cosmic rays are intensifying for the 4th year in a row–an ironic side-effect of the decaying solar cycle. The new results are of interest to everyone from astronauts to air travelers.

This finding comes from a campaign of almost weekly high-altitude balloon launches conducted by the students of Earth to Sky Calculus. Since March 2015, there has been a ~13% increase in X-rays and gamma-rays over central California, where the students have launched hundreds of balloons.

The grey points in the graph are Earth to Sky balloon data. Overlaid on that time series is a record of neutron monitor data from the Sodankyla Geophysical Observatory in Oulu, Finland. The correlation between the two data sets is impressive, especially considering their wide geographic separation and differing methodologies. Neutron monitors have long been considered a “gold standard” for monitoring cosmic rays on Earth. This shows that our student-built balloons are gathering data of similar quality.

Why are cosmic rays increasing? The short answer is “Solar Minimum.” Right now, the 11-year solar cycle is plunging into one of the deepest minima of the Space Age. The sun’s weakening magnetic field and flagging solar wind are not protecting us as usual from deep-space radiation. 

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