Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsm31b1729j&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SM31B-1729
Physics
2723 Magnetic Reconnection (7526, 7835), 2744 Magnetotail, 2772 Plasma Waves And Instabilities (2471), 7863 Turbulence (4490)
Scientific paper
Recent advances in collisionless magnetic reconnection (like formation of the electron diffusion region (EDR) of scale size of electron skin depth de=c/ωpe embedded inside ion diffusion region of the scale size of ion skin depth di=c/ωpi, identification of EDR in laboratory plasma, satellite observations of electron scale structures in magnetopause (few tenth of de) and magnetotail (few de) etc.) emphasize the crucial role of electron scale physics. In this work, the electron scale processes during collisionless reconnection are simulated using the simplified electron-magnetohydrodynamic (EMHD) model, in which electron inertia provides the non-ideal effect in Ohm's law and breaks the frozen-in condition. The simulations are performed for the two cases when the simulations are initialized with (a) the longest wavelength perturbation leading to only one reconnection site in the system, and (b) with many modes leading to multiple reconnection sites in the system corresponding to the maximally growing mode. Key differences in the structures and their scale lengths in the two cases arise due to the important roles of electron flows. In case of one reconnection site, highly directed electron out flow jets lead to the bifurcation of the out of plane electron current and the length of the central reconnecting current sheet depend on the wavelength of the mode which initiated the reconnection. In the case of multiple reconnection sites, interaction of outflow jets from the neighboring reconnection sites leads to secondary instabilities which split these jets. The outflow region develops turbulence and electron vortices as a consequence of the electron Kelvin-Helmholtz instability which grows on the shear flow pattern formed by the split jets. This limits the length of the current sheet and defines the scale sizes observable by spacecraft in the Earth's magnetotail. The development of electron vortices lead to modification in the basic quadrupole structure of the out of plane magnetic field. These results has implications for the upcoming NASA's MMS mission which is designed to resolve the short scale structures ~ de. Three-dimensional studies are in progress and will be compared with these results.
Jain Nitin
Sharma Surjalal A.
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