Mason Professor Finds Direction of Magnetic Field beyond Solar System

Posted: May 11, 2007 at 1:00 am, Last Updated: November 30, -0001 at 12:00 am

By Tara Laskowski

Merav Opher, assistant professor of physics and astronomy, and her colleagues Ed Stone of the California Institute of Technology and Tamas Gombosi from the University of Michigan have published a paper in Science magazine that suggests the direction of the local interstellar magnetic field, located just outside of our solar system.

The paper, “The Orientation of the Local Interstellar Magnetic Field,” uses data sets gathered from the Voyager spacecrafts, which recently crossed the termination shock at the edge of the solar system after having been launched in 1977.

Up to now, scientists have believed that the magnetic field outside of our solar system was parallel to the galactic plane. But Opher, Stone and Gombosi used two data sets to conclude that the magnetic field is actually 60-90 degrees perpendicular to the plane.

Their data also strongly suggests that the solar system is asymmetric. While scientists thought the northern and southern hemispheres would be similar, Opher’s team has found that the southern hemisphere is more compressed due to the pull of the magnetic field. Even the eastern and western hemispheres don’t look the same, giving our solar system more of a bullet shape.

image of solar system movement
A 3D rendition of the heliosphere as seen from outside the solar system shows that the heliosphere is distorted in the direction of the interstellar magnetic field. The interstellar field lines are shown wrapping around the heliosphere (solar system).
Image courtesy Merav Opher

“Scientists have often looked at the larger scale magnetic fields of the galaxy. The work we are doing is on a much smaller scale, looking just beyond our solar system. It is like looking at our backyard as opposed to looking at the country,” says Opher. “For the first time we know what the local magnetic field looks like, and astronomers will be very excited about this.”

Opher is the only female scientist – and by far one of the youngest scientists – working to calculate the flow of particles and magnetic fields at the edge of the solar system.

Many millions of miles past Pluto, the solar wind of our sun begins to lose its dominance when it comes into contact with the interstellar wind from the rest of our galaxy. Scientists consider the place where the two winds meet – called the heliopause – as the edge of our solar system. Opher analyzed radio emissions from the heliopause and the streaming direction of ions from the termination shock, which is the area where the million-mile-per-hour solar wind slows to about 250,000 miles per hour.

Their work suggests that the field orientation of the local magnetic field differs from that of a larger scale interstellar magnetic field thought to parallel the galactic plane. This conclusion will have an enormous impact on the way physicists and astronomers measure the physics and properties of the areas beyond our solar system.

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