DULUTH — As I write, a blast of particles from the sun has already buffeted Earth's magnetic domain. Predicted to arrive this evening, the material from a March 10 coronal mass ejection instead showed up early, sparking a spectacular aurora display over Alaska this morning. With a bit of luck, the auroras will continue into the night, when skywatchers in the northern states will get their chance. The latest space weather forecast predicts minor to moderate storming from nightfall Sunday to around 1 a.m. Monday morning Central Daylight Time.

The numbers show a minor G1 storm from nightfall until around 10 p.m., with activity increasing to moderate (G2) from 10 p.m. through 1 a.m. Unfortunately, the waxing gibbous moon will affect the view, likely washing out the early aurora, making it nearly impossible to see except in camera time exposures. If the storm swells to a G2, where bright arcs and rays are common, we'll fare better. Best time to watch will be between 10 p.m. and 1 a.m.

The culprit behind today's storm is an innocent-looking gray stripe hovering above the sun's surface called a filament. Filaments look like centipedes, but they're actually incandescent hydrogen gas suspended "in the air" by invisible magnetic fields. When visible at the sun's edge we see them as bright, pink flames called prominences. Filaments and prominences are one and the same. Occasionally, the magnetic field supporting the filament shifts and sends the filament bounding into space. That's what happened on March 10, with the material producing the halo CME event that we hope will bring dancing lights to our sky Sunday night.

The spring and fall equinoxes are often best for seeing auroras at mid-latitudes. In part, this has to do with the tilt of the sun's axis, which is tipped 7.25° in relation to Earth's orbit. The steady stream of particles blowing from the sun called the solar wind blasts more strongly from the polar regions than the equator by about 30 miles a second (50 km/sec).

In March, when the sun's south pole tips in Earth's direction, we get blasted by higher "winds," which can boost the possibility for auroras. In September, we face the north pole more directly, which elevates the chances for auroras once again.

The sun, which resembles a giant magnet with north and south poles, rotates on its axis roughly once every four weeks. As it spins, the solar magnetic field spirals outward across the solar system like ripples on a pond. In April and October (also great aurora months), Earth's magnetic field aligns most closely with the sun's, increasing the chances of the two connecting. Once that connection is established, particles in the solar wind can funnel down into the atmosphere in the polar regions and spark auroral displays.

Let's hope all these factors add up to some aurora Sunday night! I'll be monitoring and will update on my Facebook page .

"Astro" Bob King is a freelance writer for the Duluth News Tribune.