ANCHORAGE, Alaska (KTUU) – Most experienced aurora chasers know there is a pattern to the aurora—an eleven year solar cycle. When the solar cycle is its peak, Earth experiences lots of aurora. At its minimum, sky-watchers have fewer chances to see the northern lights. The last maximum was 2013. The sun is heading into its minimum.
Aurora over Bethel, April 20, 2018.
The phenomenon is the result of the sun’s magnetic field.
“Because the sun is a ball of plasma rather than a solid object like the Earth, as it rotates, the equator actually rotates faster than the rest of the sun,” explains Erin Hicks, Assistant Professor of Astronomy at the University of Alaska-Anchorage. This causes the sun’s magnetic field—which is anchored into the plasma—to get twisted.
“As it does that, we see more sunspots,” says Hicks. “We see more activity on the sun, big ejections of material that go out into the solar system sometimes toward Earth and then it will settle down.”
The solar minimum—which means fewer aurora viewing chances—is when the sun’s magnetic field settles down and moves in a more orderly fashion.
Even with the sun nearing its solar minimum, this winter has had pretty good aurora. Hicks says that just because there aren’t as many massive explosions, there is still a steady stream of charged particles that hit the Earth’s atmosphere.
“The sun is still a very active body in our solar system,” says Hicks. “For example, there can be more steady streams of charged particles, from the sun during these solar minimums. So although we don’t have the big violent events that carry charged particles in our direction, there’s still a steady stream, more of the solar wind effect.”