New data from cosmic ray balloons show that Solar Cycle 25 is having an effect on Earth's atmosphere. Radiation levels in the air above our heads is decreasing as the new solar cycle gains strength. Spaceweather.com and the students of Earth to Sky Calculus have been monitoring the situation for more than 6 years, and here are the latest data:

The plot shows cosmic rays in the stratosphere, measured by radiation sensors we launch almost once a week from the Sierra Nevada mountains in California. Recent flights confirm that radiation levels are decreasing for the first time since 2015.

Cosmic rays come from deep space--mostly from supernova explosions. To reach the inner solar system, they have to fight their way through the sun's protective magnetic field. Once cosmic rays reach Earth, they crash into the top of our atmosphere, creating a spray of secondary radiation, which we measure using high-altitude balloons.

Atmospheric radiation shot up in 2015-2019 because then-Solar Cycle 24 was decaying. The sun's magnetic field became weak and uncomplicated; cosmic rays from deep space found it easier to reach us. Our highest measurements in late 2019 correspond with NOAA's official date of Solar Minimum. Now the sun is waking up again. New Solar Cycle 25 is strengthening the sun's magnetic shield, and atmospheric radiation is dropping.

Above: In search of data, Earth to Sky student Joey Harvey hikes through the Saline Range in Death Valley National Park.

Every time we launch a balloon we have to recover the payload to get the results--often from rugged mountain peaks and remote deserts. There's a little blood, sweat and/or tears in each data point. For many of us, this is the best part of the program. Our adventures have resulted in an uninterrupted record of in situ atmospheric radiation measurements now straddling two solar cycles.

More information and some technical details may be found here.