A Theory For Everything
Researchers from the U.S. DOE's Princeton Plasma Physics Laboratory (PPPL) and Princeton University may have solved the mystery surrounding magnetic reconnection, bringing us one step closer to better solar flare prediction and (pmost notably) problems surrounding nuclear fusion containment. Ultimately, this means that nuclear fusion, and the limitless energy it could provide, may be one step closer to reality.
But to step back for a moment, magnetic reconnection is a process that occurs when magnetic field lines embedded in plasma come together, break apart, and explosively reconnect. This occurs in thin plasma sheets where electric energy is concentrated.
The whole process is described by the Sweet-Parker model. But the theory fails to explain why magnetic reconnection seems to be moving faster than what is predicted.
The new research details a way to explain the occurrence of fast reconnection, using a phenomenon called plasmoid instability. It's what happens when the plasma sheets start breaking into plasma "islands."
The researchers were able to come up with a general theory of the plasmoid instability, and they say that plasmoid instability starts with a linear phase that follows Sweet-Parker, which then accelerates into an explosive phase that speeds up reconnection.
They calculated how long each of these phases occurs and the physics behind each one. In the end, they learned that the process doesn't follow power laws, which means that decreasing instability isn't going to impact reconnection speed in a predictable way.
The discovery is significant if you consider that magnetic reconnection powers solar flares, the northern lights, gamma-ray bursts, and other violent natural phenomena. Calculating just when reconnection speeds up in the Sun means we can predict solar flares, solar storms, and other freak space weather.
But it also has an effect on how we look at nuclear fusion. One of the most prominent ways of generating nuclear fusion is using tokamak fusion reactors. These trap plasma in magnetic fields in specific areas to force hydrogen to fuse.
In experiments, magnetic reconnection can break these fields. This weakens the hold on the plasma, meaning it can reach areas in the containment field that won't allow fusion to sustain itself. This discovery means we can find ways to strengthen these magnetic barriers, making for better fusion experiments.