April 5, 2013, 12:00 pm - 1:00 pm

April 5, 12:00 pm - 1:00 pm

Laboratory Study of Magnetic Reconnection: Recent discoveries on how it works in the two fluid regime and energizes plasma particles

Masaaki Yamada,Princeton Plasma Physics Laboratory

Magnetic reconnection is a phenomenon of nature in which magnetic field lines change their topology in plasma and convert magnetic energy to particles by acceleration and heating. It is one of the most fundamental processes at work in laboratory and astrophysical plasmas. Magnetic reconnection occurs everywhere: in solar flares; coronal mass ejections; the earth’s magnetosphere; in the star forming galaxies; and in plasma fusion devices. This talk focuses on recent discoveries in the fundamental research of magnetic reconnection at Princeton Plasma Physics Laboratory and its application to space astrophysical plasmas. We compare the experimental results from the Magnetic Reconnection Experiment (MRX) with those from theory and numerical simulations. The collaboration between space and laboratory scientists on reconnection research has recently reached a point where we can compare measurements of the reconnection layer profile in detail with support from numerical simulations. In spite of the huge difference in physical scales, we find remarkable commonalities in the features of the magnetic reconnection region in laboratory and space-astrophysical plasmas.

Recently the physics of the reconnection layer has moved forward through understanding of the local physics of collision-less magnetic reconnection. Two-fluid dynamics have been verified through experimental identification of both the ion and electron diffusion layers. The measured in-plane plasma potential profile, which is established by electrons accelerated around the electron diffusion region, shows a saddle-shaped structure that is wider and deeper towards the outflow direction. This potential structure ballistically accelerates ions near the separatrices toward the outflow direction. Ions are heated as they travel into the high pressure downstream region. The effects of guide field on reconnection have also been studied by systematically varying the applied guide field to values much greater than the reconnecting field. Guide field is observed to significantly decrease the reconnection speed and the quantitative relationship of reconnection rate with guide field will be presented.

(1) M. Yamada, R. Kulsrud, H. Ji, Rev. Mod. Phys. v.82, 602 (2010)