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Hybrid simulations are performed to investigate the dynamics of both solar wind protons and interplanetary pickup ions (PUIs) around the corotating interaction region (CIR). The one-dimensional system is applied in order to focus on processes in the direction of CIR propagation. The CIR is bounded by forward and reverse shocks, which are responsible for particle acceleration. The effective acceleration of solar wind protons takes place when the reverse shock (fast wind side) favors a quasi-parallel regime. The diffusive process accounts for this acceleration, and particles can gain energy in a suprathermal range (on the order of 10 keV). In contrast, the PUI acceleration around the shock differs from the conventional model in which the motional electric field along the shock surface accelerates particles. Owing to their large gyroradius, PUIs can gyrate between the upstream and downstream, several proton inertial lengths away from the shock. This “cross-shock” gyration results in a net velocity increase in the field-aligned component, indicating that the magnetic mirror force is responsible for acceleration. The PUIs that remain in the vicinity of the shock for a long duration (tens of gyroperiods) gain much energy and are reflected back toward the upstream. These reflected energetic PUIs move back and forth along the magnetic field between a pair of CIRs that are magnetically connected. The PUIs are repeatedly accelerated in each reflection, leading to a maximum energy gain close to 100 keV. This mechanism can be evaluated in terms of “preacceleration” for the generation of anomalous cosmic rays. [ABSTRACT FROM AUTHOR] more...

The damping process of field-aligned, low-frequency right-handed polarized nonlinear Alfvén waves (NAWs) in solar wind plasmas with and without proton beams is studied by using a two-dimensional ion hybrid code. The numerical results show that the obliquely propagating kinetic Alfvén waves (KAWs) excited by beam protons affect the damping of the low-frequency NAW in low beta plasmas, while the nonlinear wave-wave interaction between parallel propagating waves and nonlinear Landau damping due to the envelope modulation are the dominant damping process in high beta plasmas. The nonlinear interaction between the NAWs and KAWs does not cause effective energy transfer to the perpendicular direction. Numerical results suggest that while the collisionless damping due to the compressibility of the envelope-modulated NAW plays an important role in the damping of the field-aligned NAW, the effect of the beam instabilities may not be negligible in low beta solar wind plasmas. [ABSTRACT FROM AUTHOR] more...

In the present study, the dissipation processes of circularly polarized Alfvén waves in solar wind plasmas including beam components are numerically discussed by using a 2-D hybrid simulation code. Numerical results suggest that the parent Alfvén waves are rapidly dissipated due to the presence of the beam-induced obliquely propagating waves, such as kinetic Alfvén waves. The nonlinear wave-wave coupling is directly evaluated by using the induction equation for the parent wave. It is also observed both in the 1-D and 2-D simulations that the presence of large amplitude Alfvén waves strongly suppresses the beam instabilities. [ABSTRACT FROM AUTHOR] more...

Nonlinear scattering of protons and alpha particles during the dissipation of the finite amplitude, low-frequency Alfvénic turbulence is studied. The process discussed here is not the coherent scattering and acceleration, as those often treated in the past studies, but is an incoherent process in which it is essential that the Alfvénic turbulence has a broadband spectrum. The presence of such an Alfvénic turbulence is widely recognized observationally both in the solar corona and in the solar wind. Numerical results suggest that, although there is no apparent sign of the occurrence of any parametric instabilities, the ions are heated efficiently by the nonlinear Landau damping, i.e., trapping and phase mixing by Alfvén wave packets which are generated by beating of finite amplitude Alfvén waves. The heating occurs both in the parallel and in the perpendicular directions, and the ion distribution function which is asymmetric with respect to the parallel velocity is produced. Eventual perpendicular energy of ions is much influenced by the spectrum and polarization of the given Alfvénic turbulence since the turbulence initially possess transverse energy as specified by Walen’s relation. [ABSTRACT FROM AUTHOR] more...

Nonlinear evolution of broadband spectrum Alfvénic turbulence is studied by using one-dimensional hybrid simulations. Numerical solutions indicate that the important characteristics in the solar wind magnetohydrodynamic (MHD) turbulence are naturally reproduced by nonlinear evolution of Alfvénic turbulence with more realistic power spectrum than one used in the past studies. Namely, (i) the modulational instability can dissipate the magnetic energy of Alfvénic turbulence and preserve the Alfvénicity even in low beta plasmas. (ii) Nonlinear evolution of the Alfvénic turbulence can induce the generation of the localized structures in the solar wind MHD turbulence. [ABSTRACT FROM AUTHOR] more...

Large amplitude, low-frequency Alfvén waves constitute one of the most essential elements of magnetohydrodynamic (MHD) turbulence in the fast solar wind. Due to small collisionless dissipation rates, the waves can propagate long distances and efficiently convey such macroscopic quantities as momentum, energy, and helicity. Since loading of such quantities is completed when the waves damp away, it is important to examine how the waves can dissipate in the solar wind. Among various possible dissipation processes of the Alfvén waves, parametric instabilities have been believed to be important. In this paper, we numerically discuss the parametric instabilities of coherent/incoherent Alfvén waves in a finite ion beta plasma using a one-dimensional hybrid (superparticle ions plus an electron massless fluid) simulation, in order to explain local production of sunward propagating Alfvén waves, as suggested by Helios/Ulysses observation results. Parameter studies clarify the dependence of parametric instabilities of coherent/incoherent Alfvén waves on the ion and electron beta ratio. Parametric instabilities of coherent Alfvén waves in a finite ion beta plasma are vastly different from those in the cold ions (i.e., MHD and/or Hall-MHD systems), even if the collisionless damping of the Alfvén waves are neglected. Further, “nonlinearly driven” modulational instability is important for the dissipation of incoherent Alfvén waves in a finite ion beta plasma regardless of their polarization, since the ion kinetic effects let both the right-hand and left-hand polarized waves become unstable to the modulational instability. The present results suggest that, although the antisunward propagating dispersive Alfvén waves are efficiently dissipated through the parametric instabilities in a finite ion beta plasma, these instabilities hardly produce the sunward propagating waves. [ABSTRACT FROM AUTHOR] more...

Abstract: We have investigated the electric-field-induced resistance-switching phenomena using Al and Ni electrodes on epitaxial NiO films with various resistivities. For excluding effects due to grain boundaries and roughness of NiO–electrode interfaces, epitaxial NiO films having atomically flat surfaces and high crystalline quality were fabricated by pulsed laser deposition. It is suggested that the resistance switching occurs around Al–NiO interfaces since only the electrode pairs including Al exhibit the resistance switching. Furthermore, this resistance switching strongly depends on NiO film resistivities, indicating that carrier density is also an important factor for resistance switching. [Copyright &y& Elsevier] more...