University of California scientists
working at Los Alamos National Laboratory have proposed a new theory
to explain the movement of vast energy fields in giant radio
galaxies (GRGs). The theory could be the basis for a whole new
understanding of the ways in which cosmic rays — and their
signature radio waves — propagate and travel through intergalactic
space.
In a paper published this month in The Astrophysical Journal
Letters, the scientists explain how magnetic field reconnection may
be responsible for the acceleration of relativistic electrons within
large intergalactic volumes. That is, the movement of charged
particles in space that are originally energized by massive black
holes.
“If our understanding of this process is correct,” says Los Alamos
astrophysicist Philipp Kronberg, “it could be a paradigm shift in
current thinking about the nature of GRGs and cosmic rays.”
Researchers still do not fully understand why magnetic field
reconnection occurs, but this much is known: a deeper understanding
of the mechanism could have important applications here on Earth,
such as the creation of a system of magnetic confinement for fusion
energy reactors.
If the Los Alamos scientists’ theory is correct, the discovery also
has wide-ranging astrophysical consequences. It implies that
magnetic field reconnection or some other highly efficient
field-to-particle energy conversion process could be a principal
source of all extragalactic radio sources, and possibly also the
mysterious “Ultra High Energy Cosmic Ray particles”.
Giant radio galaxies are vast celestial objects that emit a
continuum of radio wavelengths detectable with radio telescopes like
those at the Very Large Array in Socorro, N.M. Using comprehensive
data on seven of the largest radio galaxies in the Universe gathered
over the past two decades, the researchers were able to study cosmic
ray energy fields that are expelled from the GRGs centers — which
are almost certain to contain supermassive black holes — outward as
much as a few millions of light years into intergalactic space (1
light year = 5,900,000,000,000 miles).
What the Los Alamos researchers concluded was that the high energy
content of these giant radio galaxies, their large ordered magnetic
field structures, the absence of strong large-scale shocks and very
low internal gas densities point to a direct and efficient
conversion of the magnetic field to particle energy in a process
that astrophysicists call magnetic field reconnection. Magnetic
field reconnection is a process where the lines of a magnetic field
connect and vanish, converting the field’s energy into particle
energy. Reconnection is considered a key process in the sun’s
corona for the production of solar flares and in fusion experiment
devices called tokamaks. It also occurs in the interaction between
the solar wind and the Earth’s magnetic field and is considered a
principal cause of magnetospheric storms.
The research determined that the measurement of the total energy
content of at least one of these giant radio galaxies — which is
believed to have at its center a black hole with a mass equal to 100
million times that of our sun — was 1061 ergs. Ergs are a measure
of energy where one erg is the amount of energy needed to lift one
gram of weight a distance of one centimeter. This energy level of
1061 ergs is several times more than the thermonuclear energy that
could be released by all the stars in a galaxy, offering substantial
proof to the researchers that the source of the measured energy
could not be typical solar fusion or even supernovae.
In addition to the high energy content, the large, orderly structure
of the magnetic field and the absence of strong large-scale shocks
— like those that might be present from a supernova explosion —
led the scientists to believe that the process of magnetic field
reconnection is at work.
In addition to Kronberg, the theory is the result of work by Los
Alamos scientists Stirling Colgate, Hui Li and Quentin Dufton. The
research was funded by Los Alamos Laboratory-Directed Research and
Development (LDRD) funding. LDRD funds basic and applied research
and development focusing on creative concepts selected at the
discretion of the Laboratory Director.
Los Alamos National Laboratory is operated by the University of
California for the National Nuclear Security Administration (NNSA)
of the U.S. Department of Energy and works in partnership with
NNSA’s Sandia and Lawrence Livermore national laboratories to
support NNSA in its mission.
Los Alamos enhances global security by ensuring safety and
confidence in the U.S. nuclear stockpile, developing technologies to
reduce threats from weapons of mass destruction and improving the
environmental and nuclear materials legacy of the cold war. Los
Alamos’ capabilities assist the nation in addressing energy,
environment, infrastructure and biological security problems
