Japanese researchers claim they have invented a strategy for correctly forecasting the main driver for solar flares.
As magnetic fields on and around the Sun reconnect, solar flares form. Although most solar flares are harmless, large amounts of energy collecting near sunspots can be emitted, throwing plasma and high-energy particles into space. Also flares that are not Carrington-level events will cause severe electrical, communication, and transport network disturbances. An accurate way to forecast hazardous solar flares may help policymakers reduce their impact.
Previous attempts have been focused on observations of sunspots to predict flare behavior, for example, calculating flare size on the basis of sunspot and magnetic field properties.
The researchers of Nagoya University and the National Astronomical Observatory of Japan identify what they call "a physics-based approach that can forecast imminent massive solar flares" in a paper published this summer in Science.
The method is based on the insight that comparatively minor reconfigurations in the magnetic field lines of the Sun can induce major disruption, not unlike how avalanches can be caused by small gaps in the snow covering a mountain.
Only data relating to the solar magnetic field is used in the process. To measure the three-dimensional field above the surface, two-dimensional surface magnetic field data is fed into a supercomputer. The equations are based on magnetohydrodynamics (MHD), under the control of magnetic and electrical fields, the study of electrically conductive fluids and plasma.
The researchers found that a new kind of MHD instability, called double-arc instability, can serve as an initial driver of solar flares, a sort of M-shaped structure of magnetic field lines. The study also explains how the researchers used a new parameter called the density of magnetic twist flux, a reading taken on the solar surface near the magnetic polarity inversion line.
"Instability and magnetic reconnection were separately investigated as the initial driver of solar flares," said Kanya Kusano, lead author of the study and director of the Institute for Space-Earth Environmental Research at Nagoya University. "We combined them and developed the theory of triggered instability. As a result, we developed a new scheme (the 'kappa scheme'), which can calculate how small trigger reconnections can cause a large flare and how a large flare is imminent."
It would be a struggle to bring the kappa scheme into use. Although the researchers used a supercomputer, it also took several hours to produce forecasts, and the procedure is longer than the existing method of forecasting flares.
Kusano is collaborating with the Space Weather Forecast Center at Japan's National Institute of Information and Communications Technology to minimize computing time. While he and his colleagues have been using the Solar Dynamics Observatory's findings, which are capable of continuously tracking the entire solar magnetic field, Kusano needs to use the more sensitive instruments onboard another magnetic field observatory, the Japan Aerospace Exploration Agency spacecraft Hinode.
In 2-3 years, Kusano and his team expect to see the kappa scheme applied.
