HR: 1340h
AN: SM53B-0409    [Abstracts]
TI: Role of Electron Temperature Anisotropy in the Onset of Magnetic Reconnection
AU: * Daughton, W S
EM: william-daughton@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy 511 VAN, Iowa City, IA 52242 United States
AU: Karimabadi, H
EM: homa@san.rr.com
AF: University of California San Diego, Department of Electrical and Computer Engineering 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Quest, K B
EM: quest@ucsd.edu
AF: University of California San Diego, Department of Electrical and Computer Engineering 9500 Gilman Drive, La Jolla, CA 92093 United States
AB: Predictions of tearing saturation in a neutral sheet range from small amplitude saturation to explosive growth. Using fully kinetic simulation it is demonstrated that in 2D single island tearing saturates at very small amplitudes due to preferential electron heating in the parallel direction. However, the presence of multiple unstable modes allows the system to get past the stabilization and grow to ion scales. In 3D there are two modes that can affect the nonlinear evolution of tearing. One is the Weibel instability driven by $T_{\perp e} /T_{\parallel e} <1$ and the other is the lower hybrid drift instability (LHDI). In this work the non-local linear Vlasov theory is computed for the perpendicular Weibel instability which is driven by $T_{\perp e} /T_{\parallel e} <1$. The resulting growth rate is much smaller than previous calculations and can at most increase the saturation amplitude up to the singular layer thickness. On the other hand, the LHDI can affect tearing through the generation of $T_{\perp e} /T_{\parallel e} >1$ within the current layer rather than through anomalous resistivity. When $T_{\perp e} /T_{\parallel e} >1$, the parallel Weibel/mirror instabilities merge with tearing to give rise to anisotropic tearing, which becomes the dominant instability with a broad angular spectrum. The levels of $T_{\perp e} /T_{\parallel e} >1$ generated by the LHDI significantly enhance the tearing growth rate and extend the spectrum to very short wavelengths. This expedites the transition to ion scales compared to cases where there is no LHDI.
DE: 7835 Magnetic reconnection
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting