Adjunct Professor Ethan Vishniac
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The next time your cell phone goes haywire, look to the universe for answers. Magnetic disturbances produced by the sun might be responsible. Stars and planets also produce magnetic fields. Astrophysics professor Ethan Vishniac studies the origin and behaviour of these magnetic fields, which can stretch for tens of thousands of light years.
"We see a lot of evidence for very large-scale magnetic fields that show signs of organization and coherence," said Vishniac. "They account for some of the more exciting things that happen in the universe, ranging from flares that come off the surface of our sun and occasionally disrupt telecommunications to similar flares that happen in quasars billions of light years away and produce enormous fluctuations in x-ray radiation."
The origin of these magnetic fields remains unclear, although they are maintained by spiralling charged particles. The earth's magnetic field is produced by a relatively small number of charged particles flowing within its partially liquefied core, whereas stars and galaxies are made of gases consisting of charged particles that produce magnetic fields. An object's size and speed of rotation determines the scale of its magnetic fields.
In the last decade, the theory that explained the growth of magnetic fields, which dates back to the 1950s, proved to be surprisingly inaccurate. "Before we were able to do computer simulations of three-dimensional turbulence of a fluid with charged particles in it, we had all kinds of firm ideas of how the magnetic fields would behave, and it turned out to neglect certain facts that we're now just sorting out," Vishniac explained. Those theories began to fall apart when researchers re-evaluated the basic equations and discovered that computer simulations didn't produce the results they were looking for.
According to those theories, a fluid that spiralled clockwise or counter clockwise would generate a large-scale magnetic field, but computer simulations didn't confirm those results. "We now understand there's a simple physical effect involved," said Vishniac. "In a charged fluid, the magnetic field behaves a bit like elastic threads stretched throughout the fluid. As you stretch the magnetic field lines, tension forces try to pull them back."
Modern theories suggest that magnetic field lines don't spiral in the same direction as the fluid itself. Instead, the magnetic field lines resist spiralling and must be separated into left-handed and right-handed spirals to produce a large-scale magnetic field. In order for this to happen, the magnetic field lines need to break apart, change partners and reattach in a process known as magnetic reconnection.
McMaster's Department of Physics and Astronomy offers a positive environment where faculty and students can learn from each other. "What makes a working environment good for any of us is you enjoy the people you work with, and you like to talk to them about the things you work on together," said Vishniac. As for teaching, he enjoys instilling his students with an appreciation for astrophysics. "You see if you can persuade people to be obsessed by the same things that obsess you."