Physics – Plasma Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm53b1289t&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SM53B-1289
Physics
Plasma Physics
2744 Magnetotail, 7800 Space Plasma Physics, 7829 Kinetic Waves And Instabilities, 7835 Magnetic Reconnection (2723, 7526), 7845 Particle Acceleration
Scientific paper
Magnetic reconnection is an important process to convert electromagnetic energy into plasma kinetic/thermal energy in the plasma universe. However, trigger mechanisms of the reconnection have not been fully understood well yet. The tearing mode is thought to be a direct cause of triggering the magnetic reconnection. Previous two- dimensional (2-D) full-particle simulations of the tearing mode have revealed that global reconnection picture is attained at the thickness far thinner than the ion-inertial scale. In contrast, in-situ magnetotail observations have shown the existence of the ion-scale current sheet. Recently, two key processes attracted attentions in the sense that they might play important role in explosive triggering of magnetic reconnection. The first process is the effect of the lower-hybrid drift instability (LHDI) at the edges of the current sheet. In the three-dimensional (3-D) situation, this fastest growing mode quickly leads to the spontaneous quick magnetic reconnection triggering due to the quick current sheet modification. Indeed, recent 3-D full-particle simulations have shown that even in an ion-scale current sheet, the magnetic reconnection can be triggered more quickly than 2-D situations. Can be this process operative in much thicker current sheet? The second process is the effect of the electron temperature anisotropy on the tearing mode. It has been shown that when the electron temperature perpendicular to the magnetic field is higher than that of parallel, this anisotropy boosts up the growth rate at high wave number modes of the tearing mode. In a thick current sheet favored for the electron temperature anisotropy, coalescence of small magnetic islands may lead to quick triggering of global reconnection. However, recent 2-D full-particle simulations have shown that there is a critical current sheet thickness, above which no significant saturation level was attained in the existence of the electron anisotropy. It is natural to be asked if the "ion" anisotropy might play an important role in quick magnetic reconnection triggering. In this talk, it will be reported that there is a critical thickness above which the spontaneous quick magnetic reconnection triggering ceases to exist in 3-D situation. Then, it will be reported that introduction of both the ion and electron temperature anisotropy to the 3-D system is required to revive the quick magnetic reconnection process.
Fujimoto Minoru
Shinohara Iku
Tanaka Kenny G.
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