19,676 research outputs found

    Energetic and magnetosheath energy particle signatures of the low-latitude boundary layer at low altitudes near noon

    Get PDF
    The low-latitude boundary layer (LBL) and its separation from the cusp have previously been identified using observations of particle precipitation at magnetosheath energies. Using S3-3 satellite observations, we have determined that these identifications can also be made from energetic particle observations on polar-orbiting satellites. It is found that the equatorward boundary of the LBL is identifiable as an approximately discontinuous decrease in 33-keV electron fluxes from low to high latitudes. Both the energetic ion and electron fluxes decrease discontinuously at the boundary between the LBL and the cusp or polar cap. A distinct LBL is nearly always identifiable in energetic particle measurements in the 10-14 MLT region when counting rates are statistically significant. The identifications obtained using the energetic particle measurements have been compared to those obtained using criteria developed by Newell and Meng (1988, 1989) for magnetosheath energy particle precipitation. In this way, we have evaluated the accuracy of both techniques and used the energetic particle measurements to supplement the identifications obtained using the Newell and Meng criteria. We propose that the Newell and Meng threshold on ion energy flux can be reduced by a factor of 6. This modification provides identification of the LBL for lower ion intensity levels than has previously been thought possible. Source, acceleration, and scattering processes have also been studied within and in the vicinity of the LBL. Observed trapped pitch angle distributions of energetic electrons imply that the LBL is at least partially on closed field lines. Strong scattering of energetic protons is found within and equatorward of the LBL and thus must occur at least partially along closed field lines. Field-aligned electron acceleration by parallel electric fields can be discerned within and poleward of the LBL, but a more detailed analysis is necessary for a statistical study. Conical ion acceleration was seen relatively frequently within the LBL and about half as often poleward of the LBL. Neither acceleration process could be identified anywhere equatorward of the LBL

    Triton: Topside ionosphere and nitrogen escape

    Get PDF
    The principal ion in the ionosphere of Triton is N^+. Energetic electrons of magnetospheric origin are the primary source of ionization, with a smaller contribution due to photoionization. To explain the topside plasma scale height, we postulate that N^+ ions escape from Triton. The loss rate is 3.4 × 10^7 cm^(−2) s^(−1) or 7.9 × 10^(24) ions s^(−1). Dissociative recombination of N^+_2 produces neutral exothermic fragments that can escape from Triton. The rate is estimated to be 8.6 × 10^6 N cm^(−2) s^(−1) or 2.0 × 10^(24) atoms s^(−1). Implications for the magnetosphere of Neptune and Triton's evolution are discussed

    A 233 km Tunnel for Lepton and Hadron Colliders

    Full text link
    A decade ago, a cost analysis was conducted to bore a 233 km circumference Very Large Hadron Collider (VLHC) tunnel passing through Fermilab. Here we outline implementations of e+e−e^+e^-, ppˉp \bar{p}, and μ+μ−\mu^+ \mu^- collider rings in this tunnel using recent technological innovations. The 240 and 500 GeV e+e−e^+e^- colliders employ Crab Waist Crossings, ultra low emittance damped bunches, short vertical IP focal lengths, superconducting RF, and low coercivity, grain oriented silicon steel/concrete dipoles. Some details are also provided for a high luminosity 240 GeV e+e−e^+ e^- collider and 1.75 TeV muon accelerator in a Fermilab site filler tunnel. The 40 TeV ppˉp \bar{p} collider uses the high intensity Fermilab pˉ\bar{p} source, exploits high cross sections for ppˉp \bar{p} production of high mass states, and uses 2 Tesla ultra low carbon steel/YBCO superconducting magnets run with liquid neon. The 35 TeV muon ring ramps the 2 Tesla superconducting magnets at 9 Hz every 0.4 seconds, uses 250 GV of superconducting RF to accelerate muons from 1.75 to 17.5 TeV in 63 orbits with 71% survival, and mitigates neutrino radiation with phase shifting, roller coaster motion in a FODO lattice.Comment: LaTex, 6 pages, 1 figure, Advanced Accelerator Concepts Workshop, Austin, TX, 10-15 June 201

    Wong-Zakai approximation of solutions to reflecting stochastic differential equations on domains in Euclidean spaces II

    Full text link
    The strong convergence of Wong-Zakai approximations of the solution to the reflecting stochastic differential equations was studied in [2]. We continue the study and prove the strong convergence under weaker assumptions on the domain.Comment: To appear in "Stochastic Analysis and Applications 2014-In Honour of Terry Lyons", Springer Proceedings in Mathematics and Statistic
    • …
    corecore