February 13, 2014
Ribbon Discovery At Edge Of Solar System Points To Influences From The Galactic Magnetic Field
Lee Rannals for redOrbit.com - Your Universe Online
NASA’s Interstellar Boundary Explorer (IBEX) discovered an enigmatic “ribbon” of energetic particles at the edge of our Solar System and a new study says it may be just a glimpse into how vast the influence of the galactic magnetic field really is.
The new findings offer up an explanation for the mystery on why we measure more incoming high-energy cosmic rays on one side of the sun than on the other.
"It's a fascinating time," Nathan Schwadron, of the University of New Hampshire in Durham, and first author on the paper published in Science Express, said in a statement. "Fifty years ago, we were making the first measurements of the solar wind and understanding the nature of what was just beyond near-Earth space. Now, a whole new realm of science is opening up as we try to understand the physics all the way outside the heliosphere."
IBEX detects energetic neutral atoms that form from interactions at the heliosphere’s boundaries. Charged particles must travel along the magnetic field lines that are found throughout space, and sometimes a charged particle collides with a neutral atom at the outskirts of the heliosphere and captures an electron from a neutral atom. Once this happens, the charged particle becomes electrically neutral and heads in a straight line, which can be caught by IBEX’s detectors.
Scientists can use these detections to learn more about the atoms and the magnetic field lines involved in the original collision.
The team measured super-high-energy particles to study the unequal distribution of particles as they arrive from various directions. The particles were expected to be equally distributed as they arrived from all directions.
“The teraelectronvolt (TeV) particles measured by the team are incredible,” Dr. David McComas, IBEX principal investigator and assistant vice president of the Space Science and Engineering Division at Southwest Research Institute, said in a statement. “Each one is up to 12 orders of magnitude more energetic than, for example, a photon of visible light coming from the Sun. To illustrate this scale, consider that $1 raised 12 orders of magnitude is $1,000,000,000,000 — a trillion dollars. These are super-high-energy cosmic rays made in some of the highest energy acceleration mechanisms that exist in the galaxy, such as supernovae.”
The researchers said the amount of anisotropy is small, but was clearly ordered by the galactic field around the heliosphere as measured from the IBEX ribbon. This finding suggests that the orientation of the magnetic field measured locally at our heliosphere extends much farther out into the galaxy than previously thought.
“The analysis of this important paper strongly correlates with the theoretical view of the heliosphere from the numerical model developed by our team, which uses IBEX observations to derive the interstellar magnetic field direction,” Nick Pogorelov, a space scientist at the University of Alabama in Huntsville, who works with IBEX data, said in a statement. “It shows that the heliopause that separates solar and interstellar plasmas is very long, maybe 2 trillion miles in the downwind direction, and therefore may affect the transport of high-energy cosmic rays toward the solar system.”