Key to fusion energy may be found in space

New discoveries about magnetic field lines and the first-ever direct observation of their reconnection in space are offering hope that scientists will learn how to unlock fusion power as an energy source in the future.

Nuclear fusion is a reaction between two nuclei that combine together to form a heavier nuclei. The sun shines thanks to fusion reactions that turn hydrogen nuclei into helium. Nuclear fusion is someway the opposite of current nuclear energy source used, based in fission -break- of nuclei.

Space contains magnetic fields that direct the flow of plasma, an energetic fourth state of matter consisting of positive ions and electrons. The plasma particles normally follow the paths of the magnetic field lines like streams of cars following highways.

Magnetic reconnection can release that stored energy when two magnetic field lines bend towards each other and fuse to create new field lines.

The effect frustrates efforts to create sustained energy sources through fusion. Experimental fusion reactors force atomic particles to fuse together and release energy as plasma. The plasma is contained within a “magnetic bottle,” or a cage of magnetic field lines, so that the high plasma temperatures can maintain the fusion reaction.

However, magnetic reconnection can break the magnetic bottle and allow plasma to reach the colder walls of the reactor where fusion will not sustain itself.

James Drake (university of Maryland) became interested in the topic when he looked at early fusion studies and realized how many theories at the time were “dead wrong” about magnetic reconnection. To learn more about the phenomenon, he had to look beyond Earth.

A four cluster satellite crossed through a turbulent plasma region just outside Earth’s magnetic field in January 2003, when they happened to run into an area where magnetic reconnection had occurred. Physicists thought such areas, known as electron diffusion regions, were just over six miles long and so spacecraft would probably miss them in the vastness of space.

Instead, a new look at the Cluster data showed that the electron diffusion region measured 1,864 miles long — 300 times longer than early theoretical expectations and still four times longer than seen in the latest astrophysics simulations. That also marked the first ever direct observations of magnetic reconnection in space.

Although the basic physics behind magnetic reconnection remain a mystery, Cluster promises that future missions have a good chance of further examining the phenomenon. One example is NASA’s Magnetospheric Multiscale mission, which will consist of four spacecraft that study why the plasma particles can become “unfrozen” or unstuck from the magnetic field lines they normally travel along. Magnetic reconnection is simply the most “dramatic” example of this, Drake said.

Such an energy release amounts to a conversion of magnetic energy into particle energy, which can occur in black hole jets and drives solar flares. Drake hopes to someday create a computer model that can accurately describe the conversion process — and if scientists can also apply some understanding towards future energy by fusion.