Numerical Studies of Weakly Stochastic Magnetic Reconnection

We study the effects of turbulence on magnetic reconnection using three-dimensional numerical simulations. This is the first attempt to test a model of fast magnetic reconnection proposed by Lazarian & Vishniac (1999), which assumes the presence of weak, small-scale magnetic field structure near the current sheet. This affects the rate of reconnection by reducing the transverse scale for reconnection flows and by allowing many independent flux reconnection events to occur simultaneously. We performed a number of simulations to test the dependencies of the reconnection speed, defined as the ratio of the inflow velocity to the Alfven speed, on the turbulence power, the injection scale and resistivity. Our results show that turbulence significantly affects the topology of magnetic field near the diffusion region and increases the thickness of the outflow region. We confirm the predictions of the Lazarian & Vishniac model. In particular, we report the growth of the reconnection speed proportional to ~ V^2, where V is the amplitude of velocity at the injection scale. It depends on the injection scale l as ~ (l/L)^(2/3), where L is the size of the system, which is somewhat faster but still roughly consistent with the theoretical expectations. We also show that for 3D reconnection the Ohmic resistivity is important in the local reconnection events only, and the global reconnection rate in the presence of turbulence does not depend on it.Comment: 8 pages, 8 figure

The role of pressure anisotropy in the turbulent intracluster medium

In low-density plasma environments, such as the intracluster medium (ICM), the Larmour frequency is much larger than the ion-ion collision frequency. In such a case, the thermal pressure becomes anisotropic with respect to the magnetic field orientation and the evolution of the turbulent gas is more correctly described by a kinetic approach. A possible description of these collisionless scenarios is given by the so-called kinetic magnetohydrodynamic (KMHD) formalism, in which particles freely stream along the field lines, while moving with the field lines in the perpendicular direction. In this way a fluid-like behavior in the perpendicular plane is restored. In this work, we study fast growing magnetic fluctuations in the smallest scales which operate in the collisionless plasma that fills the ICM. In particular, we focus on the impact of a particular evolution of the pressure anisotropy and its implications for the turbulent dynamics of observables under the conditions prevailing in the ICM. We present results from numerical simulations and compare the results which those obtained using an MHD formalism.Comment: 7 pages, 14 figures, Journal of Physics: Conference Serie

Reversible Superconductivity in Electrochromic Indium-Tin Oxide Films

Transparent conductive indium tin oxide (ITO) thin films, electrochemically intercalated with sodium or other cations, show tunable superconducting transitions with a maximum $T_c$ at 5 K. The transition temperature and the density of states, $D(E_F)$ (extracted from the measured Pauli susceptibility $\chi_p$ exhibit the same dome shaped behavior as a function of electron density. Optimally intercalated samples have an upper critical field $\approx 4$ T and $\Delta/{k_BT_c} \approx 2.0$. Accompanying the development of superconductivity, the films show a reversible electrochromic change from transparent to colored and are partially transparent (orange) at the peak of the superconducting dome. This reversible intercalation of alkali and alkali earth ions into thin ITO films opens diverse opportunities for tunable, optically transparent superconductors