A filamentation instability for streaming cosmic-rays

We demonstrate that cosmic rays form filamentary structures in the precursors of supernova remnant shocks due to their self-generated magnetic fields. The cosmic-ray filamentation results in the growth of a long wavelength instability, and naturally couples the rapid non-linear amplification on small scales to larger length scales. Hybrid magnetohydrodynamics--particle simulations are performed to confirm the effect. The resulting large scale magnetic field may facilitate the scattering of high energy cosmic rays as required to accelerate protons beyond the knee in the cosmic-ray spectrum at supernova remnant shocks. Filamentation far upstream of the shock may also assist in the escape of cosmic rays from the accelerator.Comment: Accepted for publication in MNRA

On the Cosmic Ray Driven Firehose Instability

The role of the non-resonant firehose instability in conditions relevant to the precursors of supernova remnant shocks is considered. Using a second order tensor expansion of the Vlasov-Fokker-Planck equation we illustrate the necessary conditions for the firehose to operate. It is found that for very fast shocks, the diffusion approximation predicts that the linear firehose growth rate is marginally faster than its resonant counterpart. Preliminary hybrid MHD-Vlasov-Fokker-Planck simulation results using young supernova relevant parameters are presented.Comment: Contribution to the 6th International Symposium on High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, Germany. To be published in the AIP Conference Proceeding

Travel Expenses In Connection With Tax-Deductible Education Expenses

Trade or business expenses are deductible if they are ordinary and necessary with respect to the trade or business in which they were incurred. Treasury Regulations bring education expenses into this purview but only if they maintain or improve skills already acquired or allow a taxpayer to maintain his current position. Related travel expenses in connection with educational activities may come into play in (i) travel to an out of town location to attend an educational function, (ii) travel while engaging in educational activities or (iii) travel which is itself a form of education.  Current regulations may limit the allowable deduction for these education-related travel expenses

The Commerce Clause From Expansion To Extortion

The Commerce Clause of the United States Constitution gave the federal government power over foreign trade, trade with the Indian tribes and trade “among several states.”  By lack of further enumeration and the passage of the Tenth Amendment to the Constitution, it would be reasonable to conclude that commerce that is truly intrastate would, therefore, be within the regulatory province of the states.  In fact, that was the interpretation initially reached and subsequently followed by the United States Supreme Court.  But in 1942, that changed and, over the course of the following 60+ years, to date the Court has concluded, by an expansive interpretation of that federal power granted, that Congress and the federal government have virtually unbridled power to regulate not only those areas that would traditionally be considered “commerce” or “interstate commerce”, but, moreover, in areas that seemingly have nothing to do with commerce, interstate, or otherwise.  This paper will trace the journey that the justices have taken down this judicial interstate highway and the methods that the federal government has employed to achieve its objectives.  Hence, the subtitle of this paper:  From Expansion to Extortion

Numerical Aspects of 3D Stellar Winds

This paper explores and compares the pitfalls of modelling the three-dimensional wind of a spherical star with a cartesian grid. Several numerical methods are compared, using either uniform and stretched grid or adaptative mesh refinement (AMR). An additional numerical complication is added, when an orbiting planet is considered. In this case a rotating frame is added to the model such that the orbiting planet is at rest in the frame of work. The three-dimensional simulations are systematically compared to an equivalent two-dimensional, axisymmetric simulation. The comparative study presented here suggests to limit the rotation rate of the rotating frame below the rotating frame of the star and provides guidelines for further three-dimensional modelling of stellar winds in the context of close-in star-planet interactions.AS thanks T. Matsakos for discussions about the modelling of star-planet systems in 3D. This work was supported by the ANR 2011 Blanc Toupies and the ERC project STARS2 (207430). The authors acknowledge CNRS INSU/PNST and CNES/Solar Orbiter fundings. AS acknowledges support from the Canada’s Natural Sciences and Engineering Research Council and from the Canadian Institute of Theoretical Astrophysics (National fellow). We acknowledge access to supercomputers through GENCI (project 1623), Prace, and ComputeCanada infrastructures

Cool Stars and Space Weather

Stellar flares, winds and coronal mass ejections form the space weather. They are signatures of the magnetic activity of cool stars and, since activity varies with age, mass and rotation, the space weather that extra-solar planets experience can be very different from the one encountered by the solar system planets. How do stellar activity and magnetism influence the space weather of exoplanets orbiting main-sequence stars? How do the environments surrounding exoplanets differ from those around the planets in our own solar system? How can the detailed knowledge acquired by the solar system community be applied in exoplanetary systems? How does space weather affect habitability? These were questions that were addressed in the splinter session "Cool stars and Space Weather", that took place on 9 Jun 2014, during the Cool Stars 18 meeting. In this paper, we present a summary of the contributions made to this session.Comment: Proceedings of the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Eds G. van Belle & H. Harris, 13 pages, 1 figur

The Housing And Economic Recovery Act Of 2008

The 2008 economic crisis world-wide was caused by many factors.  However, of the most blatant contributors in the U.S. were the failure of sub-prime mortgages and the government’s failure to properly regulate the banking loan industry. This triggered the passage of the Housing and Economic Recovery Act of 2008, which was enacted on July 30, 2008.  This Act, in the collective opinions of the authors, is a little too little and a little too late to actually remedy the massive harm caused by these types of loans and the abuses in the home loan industry

A current driven instability in parallel, relativistic shocks

Recently, Bell has reanalysed the problem of wave excitation by cosmic rays propagating in the pre-cursor region of a supernova remnant shock front. He pointed out a strong, non-resonant, current-driven instability that had been overlooked in the kinetic treatments, and suggested that it is responsible for substantial amplification of the ambient magnetic field. Magnetic field amplification is also an important issue in the problem of the formation and structure of relativistic shock fronts, particularly in relation to models of gamma-ray bursts. We have therefore generalised the linear analysis to apply to this case, assuming a relativistic background plasma and a monoenergetic, unidirectional incoming proton beam. We find essentially the same non-resonant instability noticed by Bell, and show that also under GRB conditions, it grows much faster than the resonant waves. We quantify the extent to which thermal effects in the background plasma limit the maximum growth rate.Comment: 8 pages, 1 figur

Probing cosmic ray escape from \eta\ Carinae

The binary stellar system $\eta$ Carinae is one of very few established astrophysical hadron accelerators. It seems likely that at least some fraction of the accelerated particles escape from the system. Copious target material for hadronic interactions and associated $\gamma$-ray emission exists on a wide range of spatial scales outside the binary system. This material creates a unique opportunity to trace the propagation of particles into the interstellar medium. Here we analyse $\gamma$-ray data from Fermi-LAT of $\eta$ Carinae and surrounding molecular clouds and investigate the many different scales on which escaping particles may interact and produce $\gamma$-rays. We find that interactions of escaping cosmic rays from $\eta$ Carinae in the wind region and the Homunculus Nebula could produce a significant contribution to the $\gamma$-ray emission associated with the system. Furthermore, we detect excess emission from the surrounding molecular clouds. The derived radial cosmic-ray excess profile is consistent with a steady injection of cosmic rays by a central source. However, this would require a higher flux of escaping cosmic rays from $\eta$ Carinae than provided by our model. Therefore it is likely that additional cosmic ray sources contribute to the hadronic $\gamma$-ray emission from the clouds.Comment: accepted for publication in A&A, 10 pages, 6 figure