Search Results - (Author, Cooperation:W. Lotko)
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1Latest Papers from Table of Contents or Articles in PressW. Lotko ; R. H. Smith ; B. Zhang ; J. E. Ouellette ; O. J. Brambles ; J. G. Lyon
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-07-12Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Latest Papers from Table of Contents or Articles in PressO. J. Brambles ; W. Lotko ; B. Zhang ; M. Wiltberger ; J. Lyon ; R. J. Strangeway
American Association for the Advancement of Science (AAAS)
Published 2011Staff ViewPublication Date: 2011-06-04Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
3Articles: DFG German National LicensesStaff View
ISSN: 1089-7666Source: AIP Digital ArchiveTopics: PhysicsNotes: The evolution of negative potential pulses in a magnetized plasma is studied. A three-dimensional (3-D) nonlinear ion-acoustic wave equation, including nonstationary effects of reflected electrons, has been derived from the Poisson–Vlasov equations with uniform magnetic field. In the low temperature limit, the equation is the Zakharov–Kuznetsov equation. Computer simulations of 1-D and 2-D versions of the equation have been performed. The studies show that a negative potential pulse can be enhanced by drifting electrons. The growing pulse develops asymmetrically with an oscillatory precursor and a local potential jump resembling the early phase of weak double layer formation. Two-dimensional pulses also show different scale lengths along the magnetic field and in the transverse dimension. Comparisons are made with results from particle simulations and spacecraft observations.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesStaff View
ISSN: 1089-7666Source: AIP Digital ArchiveTopics: PhysicsNotes: The evolution of weak double layers in ion-acoustic turbulence in one and two-dimensional particle simulations is examined. Weak double layers (ecursive-phi(approximately-less-than)Te) evolve in simulations when a subthermal electron drift is imposed on a long or nonperiodic system with Te/Ti(very-much-greater-than)1. Their growth rate increases with the electron drift, and they decay because of ion trapping. They do not form in weakly magnetized or unmagnetized two-dimensional (2-D) systems unless a nonuniformity is introduced in the initial or boundary conditions. When the plasma is strongly magnetized (ωce〉ωpe), they emerge from 2-D ion-acoustic turbulence as coherent structures localized transversely to the magnetic field.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 0032-0633Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: GeosciencesPhysicsType of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 0992-7689Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesPhysicsNotes: Abstract The influence of the finite ionospheric conductivity on the structure of dispersive, nonradiative field line resonances (FLRs) is investigated for the first four odd harmonics. The results are based on a linear, magnetically incompressible, reduced, two-fluid MHD model. The model includes effects of finite electron inertia (at low altitude) and finite electron pressure (at high altitude). The ionosphere is treated as a high-integrated conducting substrate. The results show that even very low ionospheric conductivity (∑P = 2 mho) is not sufficient to prevent the formation of a large-amplitude, small-scale, nonradiative FLR for the third and higher harmonics when the background transverse plasma inhomogeneity is strong enough. At the same time, the fundamental FLR is strongly affected by a state of low conductivity, and when ∑P = 2 mho, this resonance forms only small-amplitude, relatively broad electromagnetic disturbance. The difference in conductivities of northern and southern ionospheres does not produce significant asymmetry in the distribution of electric and magnetic fields along the resonant field line. The transverse gradient of the background Alfven speed plays an important role in structure of the FLR when the ionospheric conductivity is finite. In cases where the transverse inhomogeneity of the plasma is not strong enough, the low ionospheric conductivity can prevent even higher-harmonic FLRs from contracting to small scales where dispersive effects are important. The application of these results to the formation and temporal evolution of small-scale, active auroral arc forms is discussed.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesHudson, M. K. ; Lotko, W. ; Cattell, C. A. ; Lysak, R. L. ; Roth, I. ; Temerin, M.
Springer
Published 1995Staff ViewISSN: 1572-9672Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Intermediate or mesoscale processes mediate the transfer of mass, momentum, and energy across the dynamic solar wind-magnetosphere interface, and the propagation of this input through the system to the ionosphere and atmosphere. The Dartmouth-Berkeley-Minnesota theory team has identified a number of mesoscale phenomena to be investigated as part of the GGS program, including: (1) effects of upstream density fluctuations on magnetopause dynamics, (2) three-dimensional reconnection, (3) magnetopause depletion layer studies, (4) ring current interaction with Pc 1 and Pc 5 waves, (5) generation of ion Larmor-scale current layers in the near Earth plasmasheet, (6) test particle studies in the magnetotail, (7) simulation of magnetosphere- ionosphere coupling including effects of kinetic Alfvén waves and (8) auroral acceleration region studies of the effects of kinetic Alfvén waves on particle distribution functions. A broad range of techniques will be implemented including ideal and reduced MHD, two fluid, hybrid, particle-in-cell and test particle simulations. Detailed comparison of simulation results with GGS satellite and ground based data will be undertaken.Type of Medium: Electronic ResourceURL: