The spatial distribution and time evolution of impact-generated magnetic fields

The production of magnetic fields was revealed by laboratory hypervelocity impacts in easily vaporized targets. As quantified by pressure measurements, high frame-rate photography, and electrostatic probes, these impacts tend to produce large quantities of slightly ionized vapor, which is referred to as impact-generated plasma. Nonaligned electron density and temperature gradients within this plasma may lead to production of the observed magnetic fields. Past experiments were limited to measuring a single component of the impact-generated magnetic fields at only a few locations about the developing impact crater and consequently gave little information about the field production mechanism. To understand this mechanism, the techniques were extended to map the three components of the magnetic field both in space and time. By conducting many otherwise identical experiments with arrayed magnetic detectors, a preliminary 3-D picture was produced of impact-generated magnetic fields as they develop through time

Enhanced magnetic field production during oblique hypervelocity impacts

The natural remanent magnetization of the lunar surface as displayed in returned lunar samples and the data returned by the Apollo subsatellite magnetometer has an unexpectedly high magnitude and exhibits spatial variation at all scales. The origin of the lunar remanent fields may be due to crustal remanence of a core dynamo field occurring early in lunar history prior to extensive modification by impact or remanence of transient fields, particularly associated with impacts, occurring on a local scale throughout lunar history. The presence of an early core dynamo field would have strong consequences for the formation and early evolution of the Moon, yet to deconvolve the role that an internally generated core dynamo field may have had, it is necessary to understand how the magnetic state of the lunar surface has developed through time. Impact-induced magnetism may be an important component of the present magnetic state of the lunar surface. New theoretical considerations suggest that transient magnetic fields within plasma produced by hypervelocity meteorite impacts may have greater significance at larger scales than previously thought

Improving the quality of mental health services using patient outcome data: Making the most of HoNOS

Efforts to assess and improve the quality of mental health services are often hampered by a lack of information on patient outcomes. Most mental health services in England have been routinely collecting Health of the Nation Outcome Scales (HoNOS) data for some time. In this article we illustrate how clinical teams have used HoNOS data to identify areas where performance could be improved. HoNOS data have the potential to give clinical teams the information they need to assess the quality of care they deliver, as well as develop and test initiatives aimed at improving the services they provide

Elastomer Compound Developed for High Wear Applications

The U.S. Army is currently spending 300 million dollars per year replacing rubber track pads. An experimental rubber compound has been developed which exhibits 2 to 3 times greater service life than standard production pad compounds. To improve the service life of the tank track pads various aspects of rubber chemistry were explored including polymer, curing and reinforcing systems. Compounds that exhibited superior physical properties based on laboratory data were then fabricated into tank pads and field tested. This paper will discuss the compounding studies, laboratory data and field testing that led to the high wear elastomer compound

Universal trapping scaling on the unstable manifold for a collisionless electrostatic mode

An amplitude equation for an unstable mode in a collisionless plasma is derived from the dynamics on the two-dimensional unstable manifold of the equilibrium. The mode amplitude $\rho(t)$ decouples from the phase due to the spatial homogeneity of the equilibrium, and the resulting one-dimensional dynamics is analyzed using an expansion in $\rho$. As the linear growth rate $\gamma$ vanishes, the expansion coefficients diverge; a rescaling $\rho(t)\equiv\gamma^2\,r(\gamma t)$ of the mode amplitude absorbs these singularities and reveals that the mode electric field exhibits trapping scaling $|E_1|\sim\gamma^2$ as $\gamma\rightarrow0$. The dynamics for $r(\tau)$ depends only on the phase $e^{i\xi}$ where $d\epsilon_{{k}} /dz=|{\epsilon_{{k}}}|e^{-i\xi/2}$ is the derivative of the dielectric as $\gamma\rightarrow0$.Comment: 11 pages (Latex/RevTex), 2 figures available in hard copy from the Author ([email protected]); paper accepted by Physical Review Letter

Spontaneous Isotropy Breaking: A Mechanism for CMB Multipole Alignments

We introduce a class of models in which statistical isotropy is broken spontaneously in the CMB by a non-linear response to long-wavelength fluctuations in a mediating field. These fluctuations appear as a gradient locally and pick out a single preferred direction. The non-linear response imprints this direction in a range of multipole moments. We consider two manifestations of isotropy breaking: additive contributions and multiplicative modulation of the intrinsic anisotropy. Since WMAP exhibits an alignment of power deficits, an additive contribution is less likely to produce the observed alignments than the usual isotropic fluctuations, a fact which we illustrate with an explicit cosmological model of long-wavelength quintessence fluctuations. This problem applies to other models involving foregrounds or background anisotropy that seek to restore power to the CMB. Additive models that account directly for the observed power exacerbate the low power of the intrinsic fluctuations. Multiplicative models can overcome these difficulties. We construct a proof of principle model that significantly improves the likelihood and generates stronger alignments than WMAP in 30-45% of realizations.Comment: 13 pages, 10 figure