11 Jan 2006

Magnetic reconnection is a magnetic to particle energy conversion process believed to be important in astrophysics (intergalactic medium, neutron stars), solar and space physics (solar flares, coronal mass ejections, geomagnetic storms), and laboratory devices (tokamaks*). Other than in the laboratory, planetary magnetospheres and the solar wind are the only places we can study this process directly. The paper by T. D. Phan et al. addresses an aspect of reconnection that has been hotly debated. Namely, can reconnection occur over an extended region in space or is it intrinsically patchy and random?

The reported observations in the solar wind provide direct evidence that the process is fundamentally large scale and quasi-steady in nature. The 2.5 million kilometre reconnection region is a world record, 2 orders of magnitude longer than the previous record.

Largest reconnection X-line found in the solar wind between the Sun and the Earth (white line). The plasma jets directions associated with the magnetic reconnection process are symbolised by red arrows embedded in the jets (colour coded in orange). Courtesy of Matt Davis and Tai Phan, SSL, UC Berkeley, USA.

These findings are published in the 12 January 2006 issue of Nature.

T. D. Phan, J. T. Gosling, M. S. Davis, R. M. Skoug, M. Øieroset, R. P. Lin, R. P. Lepping, D. J. McComas, C. W. Smith, H. Rème, A. Balogh, A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind, Nature, Vol. 439, 12 January 2006, doi:10.1038/nature04393

* A tokamak is a torus-shaped device to contain plasma by means of strong magnetic fields. The tokamak is used for the research into nuclear fusion processes.