In a report published today, new research suggests the enigmatic "ribbon" of energeticparticles discovered at the edge of our solar system by NASA's Interstellar Boundary Explorer (IBEX)may be only a small sign of the vast influence of the galactic magnetic field.
IBEX researchers have sought answers about the ribbon since its discovery in 2009. Comprisingprimarily space physicists, the IBEX team realized that the galactic magnetic field wrapped aroundour heliosphere — the giant "bubble" that envelops and protects our solar system — appears todetermine the orientation of the ribbon and the placement of energetic particles measured in it.
An unlikely teaming of IBEX researchers with ultra-high-energy cosmic ray physicists,however, has produced complementary insights that dovetail with IBEX's studies to produce a morecomplete picture of the interactions at the solar system boundary and how they reach much fartherout into the space between the stars.
The cosmic ray physics team measured super-high-energy particles to study anisotropies, orthe unequal distribution of particles as they arrive from various directions. The particles wereexpected to be isotropic, or equally distributed as they arrived from all directions. They areindeed seen to be fairly isotropic, but with some anisotropy in different directions.
"The teraelectronvolt (TeV) particles measured by the team are incredible," says Dr. DavidMcComas, IBEX principal investigator and assistant vice president of the Space Science andEngineering Division at Southwest Research Institute. "Each one is up to 12 orders of magnitude moreenergetic than, for example, a photon of visible light coming from the Sun. To illustrate thisscale, 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 mechanismsthat exist in the galaxy, such as supernovae."
The amount of measured anisotropy is small, but clearly ordered by the galactic field thatdrapes around the heliosphere as measured from the IBEX ribbon, suggesting that the orientation ofthe magnetic field measured locally at our heliosphere extends much farther out into the galaxy thanpreviously thought. As the high-energy particles arrive from the greater galaxy, they are affectedby the magnetic field, leading to the observed anisotropy.
Thus far, combining the heliospheric and high-energy particle data into a simple model hasshown good agreement with the observed anisotropy.
Voyagers 1 and 2 kicked off this area of research by taking point measurements as theyreached the first outer boundary of our solar system in 2004 and 2007, respectively. IBEX greatlyexpanded on Voyager data by providing global images of the interactions at the boundary. In weatherterms, this is analogous to a weather satellite making regional cloud and wind maps building on thedata provided by a couple of weather stations. The addition of high-energy cosmic ray measurementsprovides data from interstellar distances, well outside our solar system — similar to a satellitegathering weather information across a continent.
Source: Southwest Research Institute