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,” said Nathan Schwadron from the IBEX Science Operations Center at the UNH Institute for the Study of Earth, Oceans, and Space.
Establishing a consistent local interstellar magnetic field direction using IBEX low-energy neutral atoms and galactic cosmic rays at energy levels 10 orders of magnitude higher 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.
“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,” said Schwadron. “That it’s revealing a consistent picture of our neighborhood 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.
“We are discovering how the interstellar magnetic field shapes, deforms, and transforms our entire heliosphere,” said David McComas from the Southwest Research Institute in San Antonio, Texas.
To date, the only other direct information gathered from the heart of this complex boundary region is from NASA’s Voyager satellites. Voyager 1 entered the heliospheric boundary region in 2004, passing beyond what’s known as the termination shock where the solar wind abruptly slows. Voyager 1 is believed to have crossed into interstellar space in 2012.
Interestingly, when scientists compared the IBEX and cosmic-ray data with Voyager 1’s measurements, the Voyager 1 data provide a different direction for the magnetic fields just outside our heliosphere.
That’s a puzzle, but it doesn’t necessarily mean one set of data is wrong and one is right. Voyager 1 is taking measurements directly, gathering data at a specific time and place, while IBEX gathers information averaged over great distances — so there is room for discrepancy. Indeed, the very discrepancy can be used as a clue — understand why there’s a difference between the two measurements and gain new insight.
“It’s a fascinating time,” said Schwadron. “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.”