Browsing by Author "Emerick, Andrew"

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    Evolution of Weak Magnetic Fields in a Turbulent Plasma
    (2013-08-09) Emerick, Andrew;
    Magnetic fields play an important role in astrophysical objects, in everything from planet for- mation through large scale structure evolution. The understanding of how these fields evolve and affect the medium in which they are contained has been bolstered through complex computational simulations of both the micro physics involved, and on cosmological scales. I focus on the context of magnetic fields in diffuse plasmas such as that present in the intracluser medium (ICM) of galaxy clusters. In this paper, I examine the evolution of initially weak magnetic fields through solenoidally driven turbulence in a plasma medium. This evolution is expected to be controlled predominantly by the small scale turbulent dynamo until the system reaches equillibrium. The relevant time domain in galaxy clusters, with eddy turnover times on the order of a few to several Myr, corresponds to well before the equillibrium stage. I focus then on the early magnetic field evolution and turbulent amplification under three initial magnetic field conditions utilizing an ideal, isothermal MHD code. I examine the detailed time and power spectra evolution of both the kinetic and magnetic energies, and compare to what would be expected in the small scale dynamo picture. In addition, I examine the prospects of distinguishing initial magnetic field structures within the ICM.
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    Examination of Radio Halos and Corresponding X-Ray Emission in Galaxy Clusters
    (2011-04-13) Emerick, Andrew; Brown, Shea; Rudnick, Lawrence
    Galaxy clusters are some of the largest structures in the visible Universe, on the order of 1-3 megaparsecs in size (~1023 meters). The process that creates these clusters and the usually strong magnetic fields within them is not well understood. Present in the center of these large scale structures is an extremely diffuse mixture of gases that emits electromagnetic radiation in the of radio waves and X-ray spectrum. It is known that, for some of these clusters, the strength of these emissions correlates well (i.e. clusters with strong X-ray emission have strong radio emission), but for many the radio emission drops significantly while the X-ray emission may still remain strong. This mechanism that causes this drop in radio is unknown, especially since much of this radio emission likely lies below the detection limit of modern radio telescopes. Using statistical image processing techniques, we sought to identify the presence of the diffuse radio emission that lies below the detection limit using observations from the Sydney University Molonglo Sky Survey of clusters in the Southern Sky, cross-referencing with X-ray images taken from . In this poster, I present a confirmation of a real detection of diffuse radio emission within these clusters. Unfortunately, the procedure used to detect this diffuse emission is unable to pinpoint which clusters, specifically, contain the diffuse emission, and which do not. Therefore, I also present attempts to narrow down which clusters contain this emission, and their correlation to the X-ray emission in each cluster. The results of this experiment serve to further the understanding of the formation and lifetime of galaxy clusters within the Universe, as well as better the methods used to observe and analyze them.
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    Simulation of Turbulence and Magnetic Field Evolution in Astrophysical Plasmas
    (2012-04-18) Emerick, Andrew
    Galaxy clusters, the largest gravitationally bound systems in the universe, are composed of hundreds to thousands galaxies, and are a few megaparsecs, or ~1023 meters, in size. These massive bodies are characterized by a hot diffuse gas within the cluster, called the intra-cluster medium (ICM). The study of the ICM is important to understanding the evolutionary process of clusters themselves. With a given set of initial conditions, computational models of the ICM observe its evolution to extract its properties at a given point in time. It is understood that the ICM is tumultuous and dynamic, which leads to turbulence that interacts with weak magnetic fields in the gas. In this project, our models of these systems seek to calculate the evolution of a diffuse turbulent gas with various initial conditions of the weak magnetic field. The primary focus is on the effects of the presence of various random magnetic fields whose vector components average to zero over the entire system. These fields, stretched and pulled by the turbulent medium, grow in magnitude until the system reaches equilibrium. The growth of the magnetic field strength and the final equilibrium states are compared to more commonly made simulations containing a uniform initial magnetic field. These simulations and comparisons give better insight into the evolution and properties of the ICM.