8,271 research outputs found

    Dissipation of the sectored heliospheric magnetic field near the heliopause: a mechanism for the generation of anomalous cosmic rays

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    The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field B{\bf B}) pressure p∥p_\parallel until the marginal firehose condition is reached, causing magnetic reconnection and associated particle acceleration to shut down. The model calls into question the strong scattering assumption used to derive the Parker transport equation and therefore the absence of first order Fermi acceleration in incompressible flows. A simple 1-D model for particle energy gain and loss is presented in which the feedback of the energetic particles on the reconnection drive is included. The ACR differential energy spectrum takes the form of a power law with a spectral index slightly above 1.5. The model has the potential to explain several key Voyager observations, including the similarities in the spectra of different ion species.Comment: Submitted to ApJ; shortened abstract; degraded figure qualit

    Quiet-time electron increases, a measure of conditions in the outer solar system

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    One possible explanation for quiet-time electron increases, increases in the intensity of 3-12 MeV interplanetary electrons that have been reported by McDonald, Cline and Simnett, is discussed. It is argued that the electrons in quiet-time increases are galactic in origin, but that the observed increases are not the result of any variation in the modulation of these particles in the inner solar system. It is suggested instead that quiet-time increases may occur when more electrons than normal penetrate a modulating region that lies far beyond the orbit of earth. The number of electrons penetrating this region may increase when field lines that have experienced an unusually large random walk in the photosphere are carried by the solar wind out to the region. As evidence for this increased random walk, it is shown that five solar rotations before most of the quiet-time increases there is an extended period when the amplitude of the diurnal anisotropy, as is measured by the Deep River neutron monitor, is relatively low. Five rotations delay time implies that the proposed modulating region lies at approximately 30 AU from the Sun, assuming that the average solar wind speed is constant over this distance at approximately 400 km/sec

    Damping of high frequency waves in the solar wind

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    Cyclotron damping by suprathermal fluxes of protons and electrons in the interplanetary medium will greatly attenuate high frequency Alfven waves and whistler waves within distances 1 AU of the sun. Electrons with energies between 50 eV to 2 KeV are heated as a result of damping interplanetary whistler waves with frequencies 2 omega meson/2 pion 30 Hz in the frame of the solar wind. This heating may account, in part, for the observed suprathermal tail of solar wind electrons. Protons with energies approximately 50 KeV damp Alfven waves with frequencies .001 omega meson/2 pion .01 Hz. This damping mechanism may explain several features of a scatter free solar electron events and high intensity, anisotropic solar proton streams

    On the anomalous component

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    The so-called anomalous cosmic ray component, which occurs at energies of about 10 MeV/nucleon and consists only of He, N, O, and Ne, has been a subject of interest for more than a decade. The origin of this component is generally considered to be interstellar neutral gas that is ionized and accelerated in the solar wind. The mechanism and the location for the acceleration, however, remains an unsolved problem. A model is used which includes the effects of gradient and curvature drifts and considers the implications of observed spatial gradients of the anomalous component for the location of the acceleration region. It is concluded that if drifts are important the acceleration region cannot lie at the solar poles. It is also concluded that there is no single region for the acceleration which can account for both the observed intensities and gradients in models which include drift effects

    The biggest challenge to fracking is no longer technological – it’s community resistance

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    The last decade has seen a renaissance in the technology used to extract shale oil and gas. But despite fracking’s positive economic impacts, some communities across the US are deeply opposed to it. Jonathan M. Fisk explores this resistance, writing that a small group of communities have responded to the fracking boom with a variety of blocks, bans and moratoriums, which can in turn spur the centralization of power by state leaders. Much of this opposition to fracking, he comments, stems from the costs local communities bear in the form of pollution and traffic, with the economic benefits tending to go the state

    The Horse\u27s Ass: A Survey of Comediology

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    What is comedy? Can someone learn to be funny? Are there rules or guidelines for the production of laughter, the universal language? This paper, which outlines an investigation of successful comedians and the production of a short film, determines to aggregate as many of the relevant prerequisites of inducing giggles as possible, especially as they relate to the audiovisual medium of cinema

    The Horse\u27s Ass: A Survey of Comediology

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    What is comedy? Can someone learn to be funny? Are there rules or guidelines for the production of laughter, the universal language? This paper, which outlines an investigation of successful comedians and the production of a short film, determines to aggregate as many of the relevant prerequisites of inducing giggles as possible, especially as they relate to the audiovisual medium of cinema

    Fracking and Goldilocks Federalism: the too loud, too quiet and just right politics of states and cities

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    2015 Spring.Includes bibliographical references.Wicked environmental and energy challenges often originate where energy, the environment and economics intersect (Rittel and Webber 1973). Fracking is one such example. As a practice, it has prompted a certain amount of political debate at both the state and municipal levels. Proponents argue that natural gas extraction creates well-paying jobs, helps grow and revive stagnant economies and that it provides a 'cleaner' burning energy source. Its opponents counter that the technique produces a number of environmental harms such as air pollution, surface and groundwater contamination, places new demands on infrastructure and causes geological instability (Davis 2012). Ranging from intergovernmental battles to cooperative relationships, the politics of fracking are reshaping the relations between neighborhoods, city hall and the statehouse. To explore the 'second order' dynamics of fracking, this dissertation asks several interrelated questions. What are the state and local institutions, rules and informal norms governing state-municipal relationships when it comes to hydraulic fracturing? To what extent do municipalities regulate fracking and what are the types of city-level regulation? Finally, why are some cities willing to pass land use policies that challenge their state's natural gas extraction goals and preemptive authority and others are not? To answer the questions above, I consider the second order dynamics in the context of Colorado, Texas and Ohio and a sample of cities in each state. Each state has a high number of citizens living near gas wells, but offers cities and towns varying degrees of land use authority. To elucidate their second-order relationships and dynamics, each chapter tests potential explanatory variables originating from studies of environmental policy, democratic theory and urban governance. Results suggest that both macro level (environmentalism and mobilization) and micro level concerns (percentage of owner occupied homes and median home values) can affect second order relations and the willingness of local communities to exert more municipal autonomy and challenge their state. My findings offer a more complete picture of second order federalism and strengthen the scholarly and applied understanding of two key American political institutions
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