The European Organization
for Nuclear Research
( CERN )
has a huge complex
of particle accelerators.
Cosmic rays are natural
high-energy particles.
They come from
distant cosmic objects,
such as exploding stars.
And they enter
our atmosphere.
It's claimed that changes
of incoming cosmic rays,
will change the quantity
of clouds, which will
affect the climate.
The CLOUD experiments
study how ions that are
produced by cosmic rays,
affect the atmosphere.
CLOUD uses a special
cloud chamber, and
a beam of particles
from their Proton
Synchrotron,
to create artificial
cosmic rays.
The chamber is inside
a thermal housing,
that precisely controls
the temperature between
-65 °C and +40 °C.
Instruments
surrounding
the chamber
continuously
analyze the
contents.
In 10 years of operation,
CLOUD made several
important discoveries
on the vapors that
form aerosol particles
in the atmosphere.
Most of CLOUD's
experiments are
aerosol runs.
Aerosols form
and grow inside
the chamber, under
simulated conditions
of sunlight and
cosmic-ray ionization.
Those aerosol particles
can seed clouds.
Most aerosol particle
formation requires
sulphuric acid.
CLOUD showed
aerosols can form
from biogenic vapors
emitted by trees.
And the aerosol
formation rate
is enhanced
by cosmic rays,
by up to 100x.
The CLOUD experiment
that started recently,
will last until the
end of November.
It is studying the ice-
and liquid-cloud-seeding
properties of various
aerosol species
grown in the chamber.
And direct effects of
cosmic-ray ionization
on clouds.
The experiment uses
several instruments
dedicated to measuring
the ice- and liquid
-cloud-seeding
properties of aerosols,
over the full range
of tropospheric
temperatures.
The CERN CLOUD team
has also built a generator
of electrically charged
cloud seeds.
It's used
to investigate
the effects of
charged aerosols,
on cloud formation
and dynamics.
"Cosmic rays, whether
natural or artificial,
leave a trail of ions
in the chamber,"
explains CLOUD
spokesperson
Jasper Kirkby,
"but the
Proton Synchrotron
provides cosmic rays
that can be adjusted
over the full range
of ionization rates
occurring in the
troposphere".
( the troposphere is the
lowest ten kilometers
of the atmosphere )
"Direct effects of
cosmic-ray ionization
on the formation of
fair-weather clouds
are highly speculative
and almost completely
unexplored experimentally,"
says Kirkby.
"So this run could be
the most boring
we've ever done
—or the most exciting!
We won't know
until we try,
but by the end of the
CLOUD experiment,
we want to be able
to answer definitively
whether cosmic rays
affect clouds
and the climate,
and not leave
any stone unturned."