A Danish experiment suggests unexpected magic by cosmic rays in cloud formation

September 04, 2013

According to the theory, small clusters of molecules in the atmosphere have difficulty growing large enough to act as "cloud condensation nuclei" on which water droplets can gather to make our familiar low-altitude clouds. The SKY2 experiment shows that the growth of clusters is much more vigorous, provided ionizing rays -- gamma rays in the experiment or cosmic rays in the atmosphere -- are present to work their chemical magic. Details of the experiment appear in the latest issue of Physics Letters A.

Back in 1996 Danish physicists suggested that cosmic rays, energetic particles from space, are important in the formation of clouds. Since then, experiments in Copenhagen and elsewhere have demonstrated that cosmic rays actually help small clusters of molecules to form. But the cosmic-ray/cloud hypothesis seemed to run into a problem when numerical simulations of the prevailing chemical theory pointed to a failure of growth.

Fortunately the chemical theory could also be tested experimentally, as was done with SKY2, the chamber of which holds 8 cubic metres of air and traces of other gases. One series of experiments confirmed the unfavourable prediction that the new clusters would fail to grow sufficiently to be influential for clouds. But another series of experiments, using ionizing rays, gave a very different result, as can be seen in the accompanying figure.

The reactions going on in the air over our heads mostly involve commonplace molecules. During daylight hours, ultraviolet rays from the Sun encourage sulphur dioxide to react with ozone and water vapour to make sulphuric acid. The clusters of interest for cloud formation consist mainly of sulphuric acid and water molecules clumped together in very large numbers and they grow with the aid of other molecules.

Atmospheric chemists have assumed that when the clusters have gathered up the day's yield, they stop growing, and only a small fraction can become large enough to be meteorologically relevant. Yet in the SKY2 experiment, with natural cosmic rays and gamma-rays keeping the air in the chamber ionized, no such interruption occurs. This result suggests that another chemical process seems to be supplying the extra molecules needed to keep the clusters growing.

"The result boosts our theory that cosmic rays coming from the Galaxy are directly involved in the Earth's weather and climate," says Henrik Svensmark, lead author of the new report. "In experiments over many years, we have shown that ionizing rays help to form small molecular clusters. Critics have argued that the clusters cannot grow large enough to affect cloud formation significantly. But our current research, of which the reported SKY2 experiment forms just one part, contradicts their conventional view. Now we want to close in on the details of the unexpected chemistry occurring in the air, at the end of the long journey that brought the cosmic rays here from exploded stars."
-end-
Prof. Svensmark and his team are in the Center for Sun-Climate Research at the Danish National Space Institute, DTU Space. His co-authors are Martin B. Enghoff and Jens Olaf Pepke Pedersen. In their paper they acknowledge important theoretical contributions to this line of research, notably from Nicolai Bork of the University of Helsinki.

Technical University of Denmark

Related Cosmic Rays Articles from Brightsurf:

Cosmic X-rays reveal an indubitable signature of black holes
A black hole is an exotic cosmic object, from within which nothing, not even light, can escape.

Cosmic rays may soon stymie quantum computing
Infinitesimally low levels of radiation, such as from incoming cosmic rays, may soon stymie progress in quantum computing.

Using lung X-rays to diagnose COVID-19
This system uses deep learning to train a neural network model that can distinguish between healthy patients, pneumonia patients and COVID-19 patients.

How cosmic rays may have shaped life
Physicists propose that the influence of cosmic rays on early life may explain nature's preference for a uniform 'handedness' among biology's critical molecules.

Galactic cosmic rays now available for study on Earth, thanks to NASA
To better understand and mitigate the health risks faced by astronauts from exposure to space radiation, we ideally need to be able to test the effects of galactic cosmic rays (GCRs) here on Earth under laboratory conditions.

Not just for bones! X-rays can now tell us about soft tissues too
A new X-ray imaging technique could identify lesions and tumors before ultrasound or MRI can.

Galactic cosmic rays affect Titan's atmosphere
Planetary scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn.

Invisible X-rays turn blue
A new reaction system can detect X-rays at the highest sensitivity ever recorded by using organic molecules.

Chest X-rays contain information that can be harvested with AI
The most frequently performed imaging exam in medicine, the chest X-ray, holds 'hidden' prognostic information that can be harvested with artificial intelligence (AI).

X and gamma rays --Even more powerful
International group of researchers including scientists from Skoltech have invented a new method for the generation of intense X and gamma-ray radiation based on Nonlinear Compton Scattering.

Read More: Cosmic Rays News and Cosmic Rays Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.