Brilliant curtains of light shimmer over Norwegian mountains on February 14—part of a recent spate of auroras that caught sky-watchers by surprise. because the displays weren't linked to specific eruptions from the sun.
Space scientists think the light shows arose due not to specific solar eruptions but to common—but no less curious—"cracks" in Earth's magnetic shield.
Such cracks form when the sun's magnetic field lines interconnect with those of the Earth. For hours at a time, charged solar particles can spill through the openings, slam into atmospheric gas, and put on dazzling displays.
(Related: "Magnetic-Shield Cracks Found; Big Solar Storms Expected.")
Interactions between the field lines often occur when there's significant solar activity, which is precisely what the sun is experiencing now as it rolls toward solar maximum—the high point in our star's roughly 11-year cycle of magnetic fluctuations. Such peaks can trigger more and stronger outflows of solar particles.
"That activity is now picking up, and we'll begin seeing more and more of these geomagnetic events and storms than we have in the previous five years," said University of California space scientist Harald Frey, an expert on cracks in Earth's magnetic field, or magnetosphere.