Scientists Identify Halting Mechanisms for Solar Eruptions

Rising from the sun’s surface like bulbous, fiery plumes, coronal mass ejections are bursts of magnetic energy from the sun’s corona. Often, these outbursts manifest as magnetic flux ropes, large and arching structures that either end in collapse or erupt outwards into surrounding space, throwing out millions of tons of plasma and radiation.

They’re considered an unpredictable threat to Earth technology and space missions. 

Researchers from the U.S. Dept. of Energy’s Princeton Plasma Physics Laboratory (PPPL) have identified a mechanism that may indicate the halt of such an eruption. The research was published in Nature.

During laboratory experiments, the researchers discovered that when the guide magnetic field—which runs along the flux rope—is strong enough to keep the rope from destabilizing, it ends up collapsing rather than erupting.

“Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic force that halts the eruptions,” according to PPPL. The lab “has discovered the importance of this force, called the ‘toroidal field tension force,’ which is missing from existing models of solar eruptions.”

The finding stemmed from the research team’s usage of the laboratory’s Magnetic Reconnection Experiment, which is a device meant for studying how magnetic fields in plasma coalesce and break apart. The researchers were able to create a flux rope, which had enough energy to drive it outwards but also had a restraining magnetic field, composed of strapping and guide fields, much like the ones keeping the rope within the solar corona on the sun.

If eruptions occurred, the researchers knew the strapping field was too weak to hold the rope down. The effect is called torus instability.

“But the researchers found that the guide field can play an important role in halting eruptions,” according to PPPL. “When the flux rope starts to move outward in the presence of a sufficiently powerful guide field, the plasma undergoes an internal reconfiguration—or ‘self-organization’—that causes the eruption to lose energy and collapse.”

The researchers suggest solar physicists turn towards guide fields when determining whether magnetic flux ropes will erupt or collapse.