Researchers have long known that solar activity and cosmic rays have a yin-yang relationship. As solar activity declines, cosmic rays intensify. Lately, solar activity has been very low indeed. Are cosmic rays responding? The answer is “yes.” Spaceweather.com and the students of Earth to Sky Calculus have been using helium balloons to monitor cosmic rays in the stratosphere. Their data show that cosmic rays in the mid-latitude stratosphere now are approximately 12% stronger than they were one year ago:

Cosmic rays, which are accelerated toward Earth by distant supernova explosions and other violent events, are an important form of space weather. They can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Among patients who have an implanted cardioverter – defibrillator (ICD), the aggregate number of life-saving shocks appears to be correlated with the number of cosmic rays reaching the ground. References: #1, #2, #3, #4.

Why do cosmic rays increase when solar activity is low? Consider the following: To reach Earth, cosmic rays have to penetrate the inner solar system. Solar storms make this more difficult. CMEs and gusts of solar wind tend to sweep aside cosmic rays, lowering the intensity of radiation around our planet. On the other hand, when solar storms subside, cosmic rays encounter less resistance; reaching Earth is a piece of cake.

Forecasters expect solar activity to drop sharply in the years ahead as the 11-year solar cycle swings toward another deep minimum. Cosmic rays are poised to increase accordingly.

For the past year, neutron monitors around the Arctic Circle have sensed an increasing intensity of cosmic rays. Polar latitudes are a good place to make such measurements, because Earth’s magnetic field funnels and concentrates cosmic radiation there. Turns out, Earth’s poles aren’t the only place cosmic rays are intensifying. Spaceweather.com and the students of Earth to Sky Calculus have been launching helium balloons to the stratosphere to measure radiation, and they find the same trend over California:

In the plot, neutron monitor measurements from the University of Oulu Cosmic Ray Station are traced in red; gamma-ray/X-ray measurements over California are denoted in gray. The agreement between the two curves is remarkable. It means that the intensification of cosmic rays is making itself felt not only over the poles, but also over lower latitudes where Earth’s magnetic field provides a greater degree of protection against deep space radiation.

Cosmic rays, which are accelerated toward Earth by distant supernova explosions and other violent events, are an important form of space weather. They can seed clouds, trigger lightning, and penetrate commercial airplanes. Indeed, our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing cosmic radiation as 2 to 5 dental X-rays. Likewise, cosmic rays can affect mountain climbers, high-altitude drones, and astronauts onboard the International Space Station.

This type of radiation is modulated by solar activity. Solar storms and CMEs tend to sweep aside cosmic rays, making it more difficult for cosmic rays to reach Earth. On the other hand, low solar activity allows an extra dose of cosmic rays to reach our planet. Indeed, the ongoing increase in cosmic ray intensity is probably due to a decline in the solar cycle. Solar Maximum has passed and we are heading toward a new Solar Minimum. Forecasters expect solar activity to drop sharply in the years ahead, and cosmic rays are poised to increase accordingly. Stay tuned for more radiation.