Friday, February 14, 2014

IBEX: Scientists reveal cosmic roadmap to galactic magnetic field

Cosmic ray intensities (left) compared with predictions (right) from IBEX. 

The similarity between these observations and predictions—as evidenced by the similar colour regions—supports the local galactic magnetic field direction determined from IBEX observations made from particles at vastly lower energies than the cosmic ray observations shown here. 

The blue area represents regions of lower fluxes of cosmic rays. 

The gray and white lines separate regions of different energies—lower energies above the lines, high energies below. 

Credit: Nathan Schwadron, UNH-EOS.

Scientists on NASA's Interstellar Boundary Explorer (IBEX) mission, including a team leader from the University of New Hampshire, report that recent, independent measurements have validated one of the mission's signature findings—a mysterious "ribbon" of energy and particles at the edge of our solar system that appears to be a directional "roadmap in the sky" of the local interstellar magnetic field.

Unknown until now, the direction of the galactic magnetic field may be a missing key to understanding how the heliosphere—the gigantic bubble that surrounds our solar system—is shaped by the interstellar magnetic field and how it thereby helps shield us from dangerous incoming galactic cosmic rays.

"Using measurements of ultra-high energy cosmic rays on a global scale, we now have a completely different means of verifying that the field directions we derived from IBEX are consistent," says Nathan Schwadron, lead scientist for the IBEX Science Operations Center at the UNH Institute for the Study of Earth, Oceans, and Space.

Schwadron and IBEX colleagues published their findings online today in Science Express.

Establishing a consistent local interstellar magnetic field direction using IBEX low-energy neutral atoms and galactic cosmic rays at ten orders of magnitude higher energy levels has wide-ranging implications for the structure of our heliosphere and is an important measurement to be making in tandem with the Voyager 1 spacecraft, which is in the process of passing beyond our heliosphere.

An all-sky map made by the IBEX spacecraft shows a surprising bright ribbon of emission coming from the edge of the solar system. 

Credit: Southwest Research Institute (SwRI)

"The cosmic ray data we used represent some of the highest energy radiation we can observe and are at the opposite end of the energy range compared to IBEX's measurements," says Schwadron.

"That it's revealing a consistent picture of our neighbourhood in the galaxy with what IBEX has revealed gives us vastly more confidence that what we're learning is correct."

How magnetic fields of galaxies order and direct galactic cosmic rays is a crucial component to understanding the environment of our galaxy, which in turn influences the environment of our entire solar system and our own environment here on Earth, including how that played into the evolution of life on our planet.

David McComas, principal investigator of the IBEX mission at Southwest Research Institute and coauthor on the Science Express paper says, "We are discovering how the interstellar magnetic field shapes, deforms, and transforms our entire heliosphere."

More information: "Global Anisotropies in TeV Cosmic Rays Related to the Sun's Local Galactic Environment from IBEX," by N.A. Schwadron et al. Science, 2014.

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