The Voyager probes sensed strong magnetic fields near the edge of our solar system, and earlier Interstellar Boundary Explorer (IBEX) results supported that. IBEX is in a high-altitude highly elliptical Earth orbit that helps it get above the Earth's magnetic field. Now, the picture is clear. There's a giant invisible space ribbon, made of energetic hydrogen atoms pumped up in energy by a galactic magnetic field.
Space is, paradoxically, both extremely empty and very full. In interstellar space (the space between stars, aka the galaxy medium), our sun's solar wind and extended magnetic field interacts with traveling cosmic rays and random interstellar clouds of mostly cold hydrogen gas. The ambient galactic magnetic field in our area is weak-- perhaps 5 milliGauss, or a fractional five one-thousands of a Gauss, versus the 50 Gauss of a refrigerator magnet or the half Gauss field of the Earth -- but potentially pervasive. A little field over a big area can have a strong effect.
So we have outward streaming particles from our sun, hitting a galactic magnetic field. What we get is the ribbon. The first reports of the invisible space ribbon were covered in Science by Richard Kerr, under the title "Tying Up the Solar System with a Ribbon of Charged Particles."
IBEX "revealed a sky-spanning "ribbon" of unexpectedly intense emissions of energetic neutral atoms (ENAs). No one knows what is creating the ENA ribbon, but everyone agrees that it means the textbook picture of the heliosphere—in which the solar system's enveloping pocket filled with the solar wind's charged particles is plowing through the onrushing "galactic wind" of the interstellar medium in the shape of a comet—is wrong."
Now further IBEX work reveals a possible cause for the ribbon. From this week's NASA press release, "We believe the ribbon is a reflection," says Jacob Heerikhuisen,.. "It is where solar wind particles heading out into interstellar space are reflected back into the solar system by a galactic magnetic field."
Since no good astronomy article neglects catastrophe, here's NASA's spiffy line, well worth me stealing here. "And upon this field, the future may hinge.".Our solar system is in a bubble, the heliosphere. The ribbon (and the Voyager probes) are near its edge, and outside are the aforementioned high energy cosmic rays zinging around, and the occasional interstellar cloud of 'stuff'. The heliosphere keeps most of that outside of our solar system, and we end up with a stable environment consisting of mostly just what the sun puts out. Baring a local supernova, we're safe. But a "strong magnetic field just outside the solar system could press against the heliosphere and interact with it in unknown ways. Will this strengthen our natural shielding—or weaken it?"
And just to be clear, we mean IBEX the satellite, not Ibex the mountain goat.
Alex, the Daytime Astronomer
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Read about my own private space venture in The Satellite Diaries