Kinetic Vlasov Simulations of collisionless magnetic Reconnection

A fully kinetic Vlasov simulation of the Geospace Environment Modeling (GEM) Magnetic Reconnection Challenge is presented. Good agreement is found with previous kinetic simulations using particle in cell (PIC) codes, confirming both the PIC and the Vlasov code. In the latter the complete distribution functions $f_k$ ($k=i,e$) are discretised on a numerical grid in phase space. In contrast to PIC simulations, the Vlasov code does not suffer from numerical noise and allows a more detailed investigation of the distribution functions. The role of the different contributions of Ohm's law are compared by calculating each of the terms from the moments of the $f_k$. The important role of the off--diagonal elements of the electron pressure tensor could be confirmed. The inductive electric field at the X--Line is found to be dominated by the non--gyrotropic electron pressure, while the bulk electron inertia is of minor importance. Detailed analysis of the electron distribution function within the diffusion region reveals the kinetic origin of the non--gyrotropic terms

Preliminary design of a mobile lunar power supply

A preliminary design for a Stirling isotope power system for use as a mobile lunar power supply is presented. Performance and mass of the components required for the system are estimated. These estimates are based on power requirements and the operating environment. Optimizations routines are used to determine minimum mass operational points. Shielding for the isotope system are given as a function of the allowed dose, distance from the source, and the time spent near the source. The technologies used in the power conversion and radiator systems are taken from ongoing research in the Civil Space Technology Initiative (CSTI) program

The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts

Copyright 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Physics of Plasmas 20, 062903 (2013) and may be found at .Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [D. Tsiklauri, Phys. Plasmas, 18, 052903 (2011)]. The numerical simulations were carried out using different density profiles and fast electron distribution functions. It is shown that electromagnetic L and R modes are excited by the transverse current, initially imposed on the system. In the course of the simulations no further interaction of the electron beam with the background plasma could be observed

Modeling of RTS noise in MOSFETs under steady-state and large-signal excitation

The behavior of RTS noise in MOSFETs under large-signal excitation is experimentally studied. Our measurements show a significant transient effect, in line with earlier reports. We present a new physical model to describe this transient behavior and to predict RTS noise in MOSFETs under large-signal excitation. With only three model parameters the behavior is well described, contrary to existing models

The peregrine falcon's rapid dive: on the adaptedness of the arm skeleton and shoulder girdle

During a dive, peregrine falcons (Falco peregrinus) can reach a velocity of up to 320 km h− 1. Our computational fluid dynamics simulations show that the forces that pull on the wings of a diving peregrine can reach up to three times the falcon’s body mass at a stoop velocity of 80 m s− 1 (288 km h− 1). Since the bones of the wings and the shoulder girdle of a diving peregrine falcon experience large mechanical forces, we investigated these bones. For comparison, we also investigated the corresponding bones in European kestrels (Falco tinnunculus), sparrow hawks (Accipiter nisus) and pigeons (Columba livia domestica). The normalized bone mass of the entire arm skeleton and the shoulder girdle (coracoid, scapula, furcula) was significantly higher in F. peregrinus than in the other three species investigated. The midshaft cross section of the humerus of F. peregrinus had the highest second moment of area. The mineral densities of the humerus, radius, ulna, and sternum were highest in F. peregrinus, indicating again a larger overall stability of these bones. Furthermore, the bones of the arm and shoulder girdle were strongest in peregrine falcons

Spacelab 3: Research in microgravity

The Spacelab 3 mission, which focused on research in microgravity, took place during the period April 29 through May 6, 1985. Spacelab 3 was the second flight of the National Aeronautics and Space Administration's modular Shuttle-borne research facility. An overview of the mission is presented. Preliminary scientific results from the mission were presented by investigators at a symposium held at Marshall Space Flight Center on December 4, 1985. This special issue is based on reports presented at that symposium

Creation of ventricular septal defects on the beating heart in a new pig model

Background/ Aims: So far, surgical and interventional therapies for muscular ventricular septal defects ( mVSDs) beyond the moderator band have had their limitations. Thus, alternative therapeutic strategies should be developed. We present a new animal model for the evaluation of such strategies. Methods: In a pig model ( n = 9), anterolateral thoracotomy was performed for exposure of the left ventricle. mVSDs were created under two- and three- dimensional echocardiography with a 7.5- mm sharp punch instrument, which was forwarded via a left ventricular puncture without extracorporeal circulation. Results: Creation of mVSDs was successful in all animals ( n = 9) confirmed by echocardiography, hemodynamic measurements and autopsy. The defects were located in the midmuscular ( n = 4), apical ( n = 1), inlet ( n = 2) and anterior part ( n = 2) of the muscular septum. All animals were hemodynamically stable for further procedures. The diameter and shunt volume of the mVSDs were 4.8 - 7.3 mm ( mean: 5.9 mm) and 12.9 - 41.3% ( mean: 22.1%), respectively. Autopsy confirmed in all animals the creation of a substantial defect. Conclusion: The described new technique for creation of an mVSD on the beating heart in a pig model is suitable for the evaluation of new therapeutic strategies for mVSD closure. Copyright (C) 2008 S. Karger AG, Basel

Clues on the obscured active nucleus of NGC 1365

Copyright © European Southern Observatory (ESO) 1999We have analyzed optical spectra (ESO-CASPEC) from the composite starburst-Seyfert galaxy NGC 1365 taken on the nucleus and the following positions (relative to nucleus): 2 arcsec N, 2 arcsec W; 2 arcsec S; 4 arcsec S; 5 arcsec S; 10 arcsec S and 20 arcsec W. A nuclear broad-line component indicative of the AGN source is confirmed in Hβ and Hα . Narrow-line widths vary between 150 and 200 km s(-1) . Extranuclear line ratios in the observed regions are mostly consistent with the lines being formed in HII regions. One of the exceptions is a rise of [OIII]lambda5007 /Hβ from 0.5 to 5 within 5 arcsec (from west to east) across the nucleus suggesting the transition from gas ionized by stars to gas ionized by the active nucleus. Faint emission-line gas observed 20 arcsec W of the nucleus (called region II) shows line ratios lying in the AGN part of diagnostic diagrams. While at first glance shocks by bar streaming motions appear to be a suggestive explanation for these line ratios we stress that there is no positive evidence for the velocities > 300 km s(-1) required for this mechanism. Another, presently more likely, explanation is that region II belongs to the far cone of the bipolar nuclear outflow which can be glimpsed through the dusty disk. Photoionization of a single-density cloud system by a diluted AGN continuum reproduces the measured line ratios, but leads via the ionization parameter to an intrinsic Hα luminosity of the obscured AGN of ~ 10(42) erg s(-1) of which less than ~ 4% are observed in the central few arcseconds. Dust obscuration could explain Hα but its concomitant gas column cannot account for the lack of Seyfert-1 typical hard X-rays from the nucleus. Based on observations collected at the European Southern Observatory, La Silla, ChileHartmut Schulz, Stefanie Komossa, Clemens Schmitz, and Anita Muck