Oct. 2, 2017 — In July 2012, a powerful solar storm almost struck Earth. Scientists estimate that had the storm, called a coronal mass ejection (CME), hit the planet, the impact would have crippled power grids worldwide, burning out transformers and instruments.
A NASA probe that happened to lie in the CME’s path detected some of the charged particles it contained. Data the satellite collected showed the storm was twice as powerful as a 1989 event that knocked out Quebec’s entire power grid, disrupted power delivery across the United States and made the northern lights visible as far south as Cuba. In fact, the recent storm might have been stronger than the first and most powerful CME known to hit the planet, the Carrington event. That 1859 storm sprayed sparks from telegraph lines, setting fire to telegraph stations. Researchers put the odds of a Carrington-size CME occurring by 2024 – and possibly hitting Earth – at 12 percent.
Such events occur when field lines in the sun’s massive magnetic system snap and reconnect. “Magnetic fields are a reservoir of an enormous amount of energy, and major eruptive events occur in which this energy is liberated,” says Amitava Bhattacharjee, a plasma physicist at the Princeton Plasma Physics Laboratory (PPPL), a Department of Energy facility in Princeton, New Jersey. “Charged particles tend to get tied to magnetic field lines like beads on a wire – when the wire breaks, the beads get thrown off at enormous speeds.”
The phenomenon, known as fast magnetic reconnection, remains a mystery. No one knows how field lines break and rejoin fast enough to expel the billions of tons of material unleashed in a CME, or even in the smaller eruptions of common solar flares. In laboratory experiments and simulations, Bhattacharjee and his colleagues have revealed new mechanisms that help explain fast magnetic reconnection.