The Effects of Turbulence on Three-Dimensional Magnetic Reconnection at the Magnetopause

Two- and three-dimensional particle-in-cell simulations of a recent encounter of the Magnetospheric Multiscale Mission (MMS) with an electron diffusion region at the magnetopause are presented. While the two-dimensional simulation is laminar, turbulence develops at both the x-line and along the magnetic separatrices in the three-dimensional simulation. The turbulence is strong enough to make the magnetic field around the reconnection island chaotic and produces both anomalous resistivity and anomalous viscosity. Each contribute significantly to breaking the frozen-in condition in the electron diffusion region. A surprise is that the crescent-shaped features in velocity space seen both in MMS observations and in two-dimensional simulations survive, even in the turbulent environment of the three-dimensional system. This suggests that MMS's measurements of crescent distributions do not exclude the possibility that turbulence plays an important role in magnetopause reconnection.Comment: Revised version accepted by GR

Fundamental length in quantum theories with PT-symmetric Hamiltonians II: The case of quantum graphs

Manifestly non-Hermitian quantum graphs with real spectra are introduced and shown tractable as a new class of phenomenological models with several appealing descriptive properties. For illustrative purposes, just equilateral star-graphs are considered here in detail, with non-Hermiticities introduced by interactions attached to the vertices. The facilitated feasibility of the analysis of their spectra is achieved via their systematic approximative Runge-Kutta-inspired reduction to star-shaped discrete lattices. The resulting bound-state spectra are found real in a discretization-independent interval of couplings. This conclusion is reinterpreted as the existence of a hidden Hermiticity of our models, i.e., as the standard and manifest Hermiticity of the underlying Hamiltonian in one of less usual, {\em ad hoc} representations ${\cal H}_j$ of the Hilbert space of states in which the inner product is local (at $j=0$) or increasingly nonlocal (at $j=1,2, ...$). Explicit examples of these (of course, Hamiltonian-dependent) hermitizing inner products are offered in closed form. In this way each initial quantum graph is assigned a menu of optional, non-equivalent standard probabilistic interpretations exhibiting a controlled, tunable nonlocality.Comment: 33 pp., 6 figure

Magnetosphere-ionosphere coupling at Jupiter:a parameter space study

Jupiter's main auroral emission is a signature of the current system that transfers angular momentum from the planet to radially outward moving Iogenic plasma. Ray et al. (2010) developed a steady state model of this current system which self-consistently included the effects of a field-aligned potential, and an ionospheric conductance modified by precipitating electrons. The presented parameter space study extends their model to explore how variations in the auroral cavity density and temperature, magnetospheric mass loading rate, and background ionospheric Pedersen conductance affect the current system and resulting auroral emission. We show that while the solutions found by Ray et al. (2010) vary with changes in the system parameters, the gross general trends remain similar to the original solutions. We find that, for an outer constraint of I100 = 86 MA, the high-latitude electron temperature and density have a lower limit of ∼1.5 keV and an upper limit of ∼0.01 cm -3, respectively, in order for solutions to be consistent with observations of Jupiter's auroral emission. For increases in the radial mass transport rate and an outer constraint of Max = 75 kV the auroral emission brightness increases

Magnetosphere-ionosphere coupling at Jupiter:Effect of field-aligned potentials on angular momentum transport

We present a time-independent model of Jupiter's rotation-driven aurora based on angular momentum conservation, including the effects of a field-aligned potential (φ∥) and an ionospheric conductivity that is modified by precipitating electrons. We argue that φ∥ arises from a limit to field-aligned current at high latitudes, and hence, we apply a current-voltage relation, which takes into account the low plasma densities at high latitudes. The resulting set of nonlinear equations that govern the behavior of angular momentum transfer is underconstrained and leads to a set of solutions, including those derived in earlier work. We show that solutions with high angular momentum transfer, large radial currents, and small mass transport rates (Ṁ ≤ 1000 kg/s) exist. Our set of solutions can reproduce many of the observed characteristics of Jupiter's main auroral oval, including the energy of the precipitating electrons, the energy flux into the ionosphere, the width of the aurora at the ionosphere, and net radial current across the field for a radial mass transport value of ∼500 kg/s

Magnetospheric Multiscale Observations Of The Electron Diffusion Region Of Large Guide Field Magnetic Reconnection

We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled t ..

Solar wind density turbulence and solar flare electron transport from the Sun to the Earth

Solar flare accelerated electron beams propagating away from the Sun can interact with the turbulent interplanetary media, producing plasma waves and type III radio emission. These electron beams are detected near the Earth with a double power-law energy spectrum. We simulate electron beam propagation from the Sun to the Earth in the weak turbulent regime taking into account the self-consistent generation of plasma waves and subsequent wave interaction with density fluctuations from low frequency MHD turbulence. The rate at which plasma waves are induced by an unstable electron beam is reduced by background density fluctuations, most acutely when fluctuations have large amplitudes or small wavelengths. This suppression of plasma waves alters the wave distribution which changes the electron beam transport. Assuming a 5/3 Kolmogorov-type power density spectrum of fluctuations often observed near the Earth, we investigate the corresponding energy spectrum of the electron beam after it has propagated 1 AU. We find a direct correlation between the spectrum of the double power-law below the break energy and the turbulent intensity of the background plasma. For an initial spectral index of 3.5, we find a range of spectra below the break energy between 1.6-2.1, with higher levels of turbulence corresponding to higher spectral indices.Comment: 9 pages, 9 figures, to be published in Ap

Efficacy of Vancomycin, Teicoplanin and Fusidic Acid as Prophylactic Agents in Prevention of Vascular Graft Infection: An Experimental Study in Rat

AbstractObjectivesTo compare the efficacy of a single prophylactic dose of intra-peritoneal vancomycin and teicoplanin with anti-biotic treated Dacron grafts (vancomycin, teicoplanin, 10 or 40% fusidic acid-soaked grafts) in preventing vascular graft infections in a rat model.DesignProspective, randomized, controlled animal study.Materials and methodsThe graft infections were established in the subcutaneous tissues of 80 female Sprague–Dawley rats by the implantation of Dacron prostheses followed by the topical inoculation with methicillin-resistant Staphylococcus aureus. The study groups were as follows: (1) uncontaminated control group, (2) untreated contaminated group, (3) contaminated group with intra-peritoneal vancomycin, (4) contaminated group with intra-peritoneal teicoplanin, (5) contaminated group received vancomycin-soaked Dacron graft, (6) contaminated group received teicoplanin-soaked Dacron graft, (7) contaminated group received 40% fusidic acid-soaked Dacron graft, and (8) contaminated group received 10% fusidic acid-soaked Dacron graft prophylaxis. The grafts were removed after 7 days and evaluated by a quantitative culture analysis.ResultsNo infection was detected in controls. The untreated contaminated group had a high bacteria count (6.0×104CFU/cm2 Dacron graft). Groups that received intra-peritoneal vancomycin or teicoplanin had less bacterial growth (4.8×103 and 3.9×103CFU/cm2 Dacron graft, respectively). Similarly, the group that received 10% fusidic acid-soaked graft showed less bacterial growth (3.6×103CFU/cm2 Dacron graft). The groups with vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts showed no evidence of infection. Statistical analyses demonstrated that intra-peritoneal prophylactic antibiotic treatment was less effective in inhibiting bacterial growth than high concentration antimicrobial-soaking of grafts.ConclusionThe use of vancomycin-, teicoplanin- and 40% fusidic acid-soaked grafts was effective in preventing primary prosthetic vascular graft infection