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.
Last month, we reported that cosmic rays are intensifying. Measurements so far in February indicate that the trend is continuing. In fact, the latest balloon flight over California on Feb. 5th detected the highest value yet:
The data show that cosmic rays in the mid-latitude stratosphere now are approximately 10% stronger than they were one year ago. All of these measurements were collected by Spaceweather.com and the students of Earth to Sky Calculus.
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.
Feb. 5, 2016: For the past week, sky watchers in the UK have witnessed a rare apparition of polar stratospheric clouds (PSCs). Normally restricted to the Arctic Circle, the fantastically colorful clouds have appeared over the British Isles almost every day since Jan. 31st. Colin Fraser photographed the display over Edinburgh, Scotland, on Feb. 2nd:
PSCs form in the lower stratosphere when temperatures drop to a staggeringly-cold -85ºC. High-altitude sunlight shining through tiny ice particles ~10µm wide produce bright iridescent colors by diffraction and interference.
But there is more to PSCs than ice. Some polar stratospheric clouds contain very small droplets of naturally occurring nitric and sulphuric acids. These droplets destroy ozone. Indeed, atmospheric optics expert Les Cowley points out that a temporary ozone hole has formed over Ireland and the UK. It is the blue patch in this Feb. 1st ozone map from NASA’s Arctic Ozone Watch:
“The acid droplets destroy the stratospheric ozone layer that protects us from harmful solar ultra-violet rays,” says Cowley. “They catalyse unreactive forms of man-made chlorine into active free radicals (for example ClO, chlorine monoxide). The radicals destroy many ozone molecules in a series of chain reactions..”
This outbreak of PSCs is truly unusual. “Prior to this outbreak I have seen PSCs over the UK only twice in the last 20 years!” says Cowley. “This episode is exceptional at such low latitudes. If it goes on any longer my camera will be worn out.”
UPDATE: On Feb. 5th, the outbreak of PSCs has subsided, and so has the UK ozone hole. Click here for updates.