ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Language
Number of Hits per Page
Default Sort Criterion
Default Sort Ordering
Size of Search History
Default Email Address
Default Export Format
Default Export Encoding
Facet list arrangement
Maximum number of values per filter
Auto Completion
Topics (search only within journals and journal articles that belong to one or more of the selected topics)
Feed Format
Maximum Number of Items per Feed
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2011-08-24
    Description: Ion pickup by the solar wind is a topic of current interest. In situ observations and theoretical studies establish a fairly good understanding of the physics of the ion-pickup process. In a weakly turbulent solar wind, hydromagnetic waves that are either intrinsic or excited by the newborn ions can lead to pitch-angle diffusion which can be approximately described by the quasi-linear theory with or without incorporating the resonance-broadening mechanism due to weak turbulence. According to the weak turbulence theory, the pickup ions do not form a complete spherical shell distribution in the time-asymptotic state unless the wave field is sufficiently strong. In some cases the ions only possess a partial or incomplete shell. When the solar wind is highly turbulent, direct interaction between the wave fields and the newborn ions can result in rapid pitch-angle scattering leading to swift formation of a spherical shell distribution on the time scale of an ion gyro-period.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 719-729 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present paper shows that the reflected ion at a supercritical quasiperpendicular shock wave can excite a purely growing m9de propagating parallel to the ambient magnetic field (k(parallel)B0). To discuss the ion heating by such an unstable mode, the self-consistent quasilinear kinetic equation is solved with the assumption that the present purely growing mode is the dominant unstable mode in the system. In the quasilinear analysis of the instability, two particular cases are considered—the case of low initial ion beta [βi(0)=0.1] and that of a high initial ion beta [βi(0)=1]. For each case of low and high initial betas, two values of initial turbulence level are used. One corresponds to δB2(0)/B20=0.1 and the other corresponding to δB2(0)/B20 =0.1. It is shown that for both low and high beta cases, the ion heating at the shock becomes more efficient for a higher value of δB2(0)/B20.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3627-3637 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the simultaneous nonlinear evolution of the Alfvén-ion-cyclotron and mirror instabilities driven by an anisotropic ion distribution function are studied. The ions are modeled by a bi-Maxwellian distribution function. For the sake of generality, two ion components are considered; the initially isotropic component and a population possessing a large temperature anisotropy with perpendicular temperature greater than parallel temperature. Here, perpendicular and parallel are defined with respect to the ambient magnetic field. The analysis is based on quasilinear kinetic theory. It is shown that initially, the mirror mode grows at a slightly faster rate when compared with the ion-cyclotron mode, but the subsequent evolution shows that the ion-cyclotron mode saturates at a much larger intensity. Simultaneously, large perpendicular temperature associated with the anisotropic ions is substantially reduced as the free energy is taken away by the unstable waves, while the parallel temperature increases so as to reduce the anisotropy. The initially isotropic ions, on the other hand, are also heated in the direction perpendicular to the ambient magnetic field vector.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2455-2462 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dispersion relation for the low-frequency electromagnetic waves propagating parallel to the ambient magnetic field is studied for a plasma comprised of energetic ring-beam distribution of ions and a background population. Detailed properties of the dispersion relation are studied for various physical parameters with particular emphasis placed on the transition from the cold case to the thermal regime. In addition, the stability characteristics are investigated for different values of α, where tan α is the ratio between the ring and the beam velocity, ranging from α=0 (pure beam) to α=90° (pure ring). The unstable modes are studied in further detail, and the dependence of the growth rate on several parameters, such as the density of the ring-beam ions and thermal speeds associated with the background and the ring-beam ions, is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2124-2132 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The freshly created ions in the upstream region of the cometary bow shock usually form a ring-beam velocity distribution in the solar wind frame of reference. These newborn ions subsequently excite a variety of instabilities which in turn cause the ions to diffuse in pitch angle space to form a quasispherical shell velocity distribution. Such a process can be described by quasilinear kinetic theory. In the present paper, the detailed properties of the initial diffusion rates associated with the cometary newborn ions are studied for various physical parameters including the so-called injection angle α (that is, the average initial pitch angle associated with the ions) ranging from 0° (pure beam distribution) to 90° (pure ring distribution). It is shown that initial diffusion rates are strongly dependent upon the angle α, such that for 0°≤α≤60° (quasiparallel regime) the pitch angle diffusion rate remains relatively small, while for 60°≤α≤90° (quasiperpendicular regime) the diffusion rate increases substantially.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1662-1665 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amplification process of a high-frequency transverse electromagnetic wave in a plasma by relativistic electrons whose momentum distribution function has an inverted population or a peak in the momentum pitch angle is known as the synchrotron maser process. In this paper, the effect of a finite temperature of the background plasma that supports the electromagnetic wave is incorporated in the analysis of the synchrotron maser mechanism. The analysis shows that the finite background temperature significantly enhances the amplification rate of the synchrotron maser process.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 842-844 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed properties of the classical hydromagnetic Alfvén wave and the fire-hose instability, driven by an excess in the parallel energy, are well understood in the nonrelativistic regime. In this Brief Communication, the analysis is extended to the fully relativistic regime. The analysis is carried out for fully relativistic bi-Maxwellian distributions of electrons and ions (or positrons). It is shown that the relativistic effect has a non-negligible effect on the wave and stability properties of the low-frequency modes under certain conditions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1971-1979 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, a generalized kinetic dispersion equation that supports various hydromagnetic waves and instabilities is derived. The general dispersion equation is derived under the usual assumption of hydromagnetic perturbations [i.e., ||ω||2(very-much-less-than)Ωi2, and (kzνA/Ωi)2(very-much-less-than)β(parallel)i, where Ωi and νA are the ion gyrofrequency and Alfvén speed, respectively, and β(parallel)i is the parallel ion beta], but for arbitrary values of the quantity λi=(k⊥ρ⊥i)2/2=(k⊥νA/Ωi)2 β⊥i/2 that appears in the dielectric tensor. Here, ρ⊥i refers to the mean ion gyroradius, and β⊥i is the perpendicular ion beta. Otherwise, the dispersion equation is fairly general with no additional approximation, such as ignoring certain off-diagonal dielectric tensor elements (which is usually done in the literature) employed. In the subsequent numerical analysis, special attention is paid to the fire-hose instability in a high beta plasma. The numerical results reveal that the conventional treatment of the fire-hose instability (i.e., taking zero ion gyroradius limit at the outset) is not adequate, and that the effect of finite ion gyroradius results in a significant enhancement of the growth rate over a large range of wave numbers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 3074-3081 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A purely growing mode propagating exactly parallel to the ambient magnetic field, driven by a cross-field current was first discussed by Chang et al. [Phys. Rev. Lett. 65, 1104 (1990)]. This paper examines the nonlinear evolution of this instability and the resulting heating of the plasma with particular emphasis on application to the quasiperpendicular collisionless shock wave. It is found that when the cross-field current is due to electrons, the instability saturates to extremely low level and the resulting heating becomes insignificant, whereas if the ions are allowed to drift the saturation level of the unstable wave is very large with substantial heating of both electrons and ions. On the other hand, if the electron drift is determined by equilibrium conditions such as the magnetic field and density inhomogeneities and local electric field at the shock front, it is found that the plasma heating becomes greatly enhanced.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1918-1927 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The weakly relativistic dielectric tensor for a system of electrons comprised of cold and energetic populations, embedded in a neutralizing background, is reformulated in terms of an infinite series representation in powers of λ=αck⊥/ωc, where α2 is a parameter proportional to the average thermal energy of the energetic electrons, k⊥ is the perpendicular component of the wave vector k, and ωc is the electron gyrofrequency. The energetic electrons are assumed to have a loss-cone feature in the perpendicular momentum space. The present formalism can be used in the problem of cyclotron maser (i.e., emissions near the fundamental ω≈ωc) as well as more general gyroharmonic maser (i.e., multiharmonics) emissions resulting from weakly relativistic loss-cone electrons. This is because, unlike the previous theories in which certain approximations such as the single-harmonic approximations are made, the present formalism retains contributions from the entire harmonics. As a result, the present formalism is valid for arbitrary ωp/ωc, where ωp is the total electron plasma frequency. As an application, growth rates for the X-mode and Z-mode gyroharmonic maser instabilities are calculated for a propagation angle θ=90° at various energies, and for ωp/ωc ranging from 0.1 to 1.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...