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First 3-D Magnetic Reconnection Measurements

Data show reconnection of two partially merging rings of plasma. The green and gray field lines represent private and reconnected field lines, respectively. The red reconnected field line crosses normal to the reconnection plane, indicating a 3-D character.
Orlando - Nov 18, 2002
In work that promises new insights into the cosmos and fusion-energy production alike, physicists have reported they have made the first three-dimensional laboratory measurements of magnetic reconnection, the main process by which magnetic fields release energy in the universe.

Magnetic reconnection is the phenomenon in which magnetic energy in a plasma is rapidly converted to heat and jets of energetic particles.

This process is thought to heat the solar corona, the outer atmosphere of the sun, to temperatures 1000 times greater than the sun's surface itself, as well as to accelerate particles to high energies, possibly even to the very high energies of cosmic rays.

Record-high magnetic fields in lab may allow re-creations of extreme astrophysical phenomena: Using a new technique, researchers from Imperial College, London, and the Rutherford Appleton lab in the UK have created super-strong magnetic fields that are hundreds of times more intense than any previous magnetic field created in an Earth laboratory and up to a billion times stronger than our planet's natural magnetic field. Such intense magnetic fields may soon enable researchers to recreate extreme astrophysical conditions, such as the atmospheres of neutron stars and white dwarfs, in their very own laboratories.

At the Rutherford Appleton Laboratory near Oxford in the UK, researchers at the VULCAN facility aimed intense laser pulses, lasting only picoseconds (trillionths of a second), at a dense plasma.

The resulting magnetic fields in the plasma were on the order of 400 MegaGauss. To determine the magnitude of the fields, the researchers made polarization measurements of high-frequency light emitted during the experiment.

Recent measurements to be presented at the APS/DPP conference suggest that the peak magnetic field in the densest region of the plasma approaches 1 GigaGauss.

Due to technological advances peak laser intensities are likely to increase still further and consequently even higher magnetic fields may soon be possible, making it possible to put models of extreme astrophysical conditions to the test.

Magnetic reconnection is also an important process in some experimental fusion energy reactors that use magnetic fields to confine the plasma.

The physical picture of magnetic reconnection is of two strands of magnetized plasma with oppositely directed magnetic field merging together. Until recently, this process has been studied only in two dimensions--theoretically, computationally, and experimentally.

Now, 3D experimental measurements of magnetic reconnection have been made at the Swarthmore Spheromak Experiment (SSX) at Swarthmore College. At SSX, physicists merge rings of magnetized plasma called spheromaks. Compact probes measure up to 600 magnetic field components more than a million times a second.

This permits detailed studies of the ever-changing 3D magnetic structures resulting from these experiments. Measurements of the spheromaks reveal a swept and sheared magnetic structure in the reconnection region (see figure).

With SSX, researchers hope to elucidate fundamental plasma physics processes on the sun and understand new plasma structures in magnetic confinement fusion machines.

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Magnetic Space Storms Accelerate Electrons To Light Speed
Berkeley - Nov 13, 2002
A chance observation of high-energy electrons emanating from a tiny region of space where the sun and Earth's magnetic fields intertwine provides the first solid evidence that a process called magnetic reconnection accelerates electrons to near the speed of light in the Earth's magnetosphere and perhaps throughout the universe where magnetic fields entangle.

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