8,384 research outputs found

    Considering Teaching Excellence in Higher Education: 2007-2013: A Literature Review Since the CHERI Report 2007

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    The acceleration of energetic particles in the interplanetary medium by transit-time damping

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    Transit time damping is examined as a possible means for accelerating low energy particles in co-rotating streams and interstellar ions. Data show that: the protons in co-rotating streams may be accelerated by transient-time damping the small-scale variations in the field magnitude that are observed at a low level in the inner solar system. The interstellar ions may be accelerated by transit time damping large-scale field variations in the outer solar system

    Solar modulation of galactic cosmic rays 4: Latitude dependent modulation

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    A numerical method is outlined for solving the equation which describes the solar modulation of cosmic rays in models where interplanetary conditions can vary with heliocentric latitude. As an illustration of the use of this method, it is shown how variations in the modulation with latitude could produce the small radial gradients in the intensity that were observed from the Pioneers 10 and 11 spacecraft

    Muon ID- Taking Care of Lower Momenta Muons

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    In the Muon package under study, the tracks are extrapolated using an algorithm which accounts for the magnetic field and the ionization (dE/dx). We improved the calculation of the field dependent term to increase the muon detection efficiency at lower momenta using a Runge-Kutta method. The muon identification and hadron separation in b-bbar jets is reported with the improved software. In the same framework, the utilization of the Kalman filter is introduced. The principle of the Kalman filter is described in some detail with the propagation matrix, with the Runge-Kutta term included, and the effect on low momenta single muons particles is described.Comment: PDF,5pages,2 Figures,1 Table,Presented at the 2005 International Linear Collider Physics and Detectors Workshop,Snowmass,Colorado,14-27 Aug. 2005, PSN1011 in the proceedin

    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

    Radial gradients and anisotropies of cosmic rays in the interplanetary medium

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    Radial gradients and anisotropies of cosmic rays in interplanetary mediu

    Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB6_6 - A weakly-nonlinear-transport study

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    We report measurements of weakly nonlinear electronic transport, as measured by third-harmonic voltage generation V3ωV_{3\omega}, in the low-carrier density semimetallic ferromagnet EuB6_6, which exhibits an unusual magnetic ordering with two consecutive transitions at Tc1=15.6T_{c_1} = 15.6\,K and Tc2=12.5T_{c_2} = 12.5\,K. Upon cooling in zero magnetic field through the ferromagnetic transition, the dramatic drop in the linear resistivity at the upper transition Tc1T_{c_1} coincides with the onset of nonlinearity, and upon further cooling is followed by a pronounced peak in V3ωV_{3 \omega} at the lower transition Tc2T_{c_2}. Likewise, in the paramagnetic regime, a drop of the material's magnetoresistance R(H)R(H) precedes a magnetic-field-induced peak in nonlinear transport. A striking observation is a linear temperature dependence of V3ωpeak(H)V_{3\omega}^{\rm peak}(H). We suggest a picture where at the upper transition Tc1T_{c_1} the coalescing MP form a conducting path giving rise to a strong decrease in the resistance. The MP formation sets in at around T∗∼35T^\ast \sim 35\,K below which these entities are isolated and strongly fluctuating, while growing in number. The MP then start to form links at Tc1T_{c_1}, where percolative electronic transport is observed. The MP merge and start forming a continuum at the threshold Tc2T_{c_2}. In the paramagnetic temperature regime Tc1<T<T∗T_{c_1} < T < T^\ast, MP percolation is induced by a magnetic field, and the threshold accompanied by charge carrier delocalization occurs at a single critical magnetization.Comment: to appear in J. Kor. Phys. Soc (ICM2012 conference contribution

    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
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