ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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: 2022-09-30
    Description: Van Allen Probes measurements revealed the presence of the most unusual structures in the ultra‐relativistic radiation belts. Detailed modeling, analysis of pitch angle distributions, analysis of the difference between relativistic and ultra‐realistic electron evolution, along with theoretical studies of the scattering and wave growth, all indicate that electromagnetic ion cyclotron (EMIC) waves can produce a very efficient loss of the ultra‐relativistic electrons in the heart of the radiation belts. Moreover, a detailed analysis of the profiles of phase space densities provides direct evidence for localized loss by EMIC waves. The evolution of multi‐MeV fluxes shows dramatic and very sudden enhancements of electrons for selected storms. Analysis of phase space density profiles reveals that growing peaks at different values of the first invariant are formed at approximately the same radial distance from the Earth and show the sequential formation of the peaks from lower to higher energies, indicating that local energy diffusion is the dominant source of the acceleration from MeV to multi‐MeV energies. Further simultaneous analysis of the background density and ultra‐relativistic electron fluxes shows that the acceleration to multi‐MeV energies only occurs when plasma density is significantly depleted outside of the plasmasphere, which is consistent with the modeling of acceleration due to chorus waves.
    Description: Plain Language Summary: The most energetic electrons in the Earth Van Allen radiation belts have not been accurately measured in the past. Observations for a recent NASA's Van Allen Probes missions reviled new unique structures, such as narrow rings, and posed further scientific questions. This review shows that, unlike relativistic electrons, ultra‐relativistic electrons can be very effectively locally scattered by plasma waves produced by ions, so‐called electromagnetic ion cyclotron waves. Observations also show that acceleration from MeV to multi‐MeV occurs locally by taking energy from another type of plasma wave. These waves are called whistler‐mode waves and can accelerate particles to such high energy when total plasma density is low. The difference between the relativistic and ultra‐relativistic particles justifies the classification of these particles into a different population from the bulk population of the outer radiation belt.
    Description: Key Points: Electromagnetic ion cyclotron waves effectively scatter ultra‐relativistic electrons in the radiation belts. The local acceleration produces acceleration from MeV to multi‐MeV in the regions of low density. The difference between MeV and multi‐MeV electrons justifies the classification of these particles into a new population.
    Description: EC, H2020, H2020 Priority Excellent Science, H2020 European Research Council http://dx.doi.org/10.13039/100010663
    Description: NASA
    Description: https://rbspgway.jhuapl.edu/
    Keywords: ddc:538.7
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2023-01-20
    Description: In this study, we present an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt based on the full data set collected by the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes in 2012–2019. The PADs are fitted with a combination of the first, third and fifth sine harmonics. The resulting equation resolves all PAD types found in the outer radiation belt (pancake, flat‐top, butterfly and cap PADs) and can be analytically integrated to derive omnidirectional flux. We introduce a two‐step modeling procedure that for the first time ensures a continuous dependence on L, magnetic local time and activity, parametrized by the solar wind dynamic pressure. We propose two methods to reconstruct equatorial electron flux using the model. The first approach requires two uni‐directional flux observations and is applicable to low‐PA data. The second method can be used to reconstruct the full equatorial PADs from a single uni‐ or omnidirectional measurement at off‐equatorial latitudes. The model can be used for converting the long‐term data sets of electron fluxes to phase space density in terms of adiabatic invariants, for physics‐based modeling in the form of boundary conditions, and for data assimilation purposes.
    Description: Plain Language Summary: Pitch angle distributions (PADs) are critically important for understanding the dynamics of trapped electrons in Earth's radiation belt region. Specific PAD types are linked to processes acting within the radiation belts which relate to the origins and loss mechanisms of the particle populations, as well as wave activity. In this study we present a polynomial model of the equatorial electron PADs at energies 30 keV–1.6 MeV with a continuous dependence on L‐shell, magnetic local time and activity driven by the solar wind dynamic pressure. The model can be used to reconstruct equatorial electron flux from observations at high latitudes and can be applied for converting the long‐term electron flux data sets to phase space density, driving the boundary conditions for the physics‐based simulations and for data assimilation.
    Description: Key Points: A sum of the first, third, and fifth sine harmonics is used to approximate equatorial electron Pitch angle distributions (PADs) measured by the MagEIS detector onboard the Van Allen Probes. We present a PAD model with a continuous dependence on L, magnetic local time and activity, driven by the solar wind dynamic pressure. The model allows reconstructions of equatorial PADs from uni‐ and omni‐directional measurements at off‐equatorial latitudes.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156
    Description: https://doi.org/10.5880/GFZ.2.7.2022.001
    Keywords: ddc:538.76 ; pitch angle ; radiation belt ; model ; magnetosphere ; van allen probes ; electrons
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2024-04-25
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉There have been a number of theories proposed concerning the loss of relativistic electrons from the radiation belts. However, direct observations of loss were not possible on a number of previous missions due to the large field of view of the instruments and often high‐altitude orbits of satellites that did not allow researchers to isolate the precipitating electrons from the stably trapped. We use measurements from the ELFIN‐L suit of instruments flown on Lomonosov spacecraft at LEO orbit, which allows us to distinguish stably trapped from the drift loss cone electrons. The sun‐synchronous orbit of Lomonosov allows us to quantify scattering that occurred into the loss cone on the dawn‐side and the dusk‐side magnetosphere. The loss at MeV energies is observed predominantly on the dawn‐side, consistent with the loss induced by the chorus waves. The companion data publication provides processed measurements.〈/p〉
    Description: Plain Language Summary: There have been a number of models proposed concerning the loss of relativistic electrons from radiation belts. However, the direct observations of loss have been missing, as for most of the previous missions; the large aperture telescopes could not isolate the precipitating electrons from being stably trapped. In this study, we use measurements from ELFIN‐L on Lomonosov that allow for such separation and allow us to distinguish stably trapped from precipitating particles. We can also identify the particles that will be lost within one drift around the Earth, the so‐called drift loss cone. For understanding the loss processes and differentiating between them, it's crucially important to quantify where in local magnetic time these electrons will be scattered into the drift loss cone. Measurements from the ELFIN‐L instrument show that the loss at MeV energies is observed predominantly on the dawn side, consistent with the loss induced by the so‐called chorus plasma waves.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉ELFIN‐L measurements allow comparing scattering into the loss cone on the dawn and dusk side〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Processed Level‐3 measurements are provided in the data publication〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Most of the relativistic electrons are scattered into the drift loss cone on the dawn side〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: National Science Foundation
    Description: Russian University Satellite Mission
    Description: Helmholtz Association
    Description: European Union's Horizon 2020 Research and Innovation Program
    Description: https://doi.org/10.5880/GFZ.2.7.2023.002
    Description: https://doi.org/10.5880/GFZ.2.7.2023.003
    Description: https://doi.org/10.5880/GFZ.2.7.2023.004
    Description: https://doi.org/10.5880/GFZ.2.7.2023.005
    Description: https://doi.org/10.5880/GFZ.2.7.2023.006
    Description: https://doi.org/10.5880/GFZ.2.7.2023.007
    Description: https://www.ncei.noaa.gov/data/poes-metop-space-environment-monitor/access/l1b/v01r00/
    Keywords: ddc:538.7 ; Electron Particle Detector ; ELFIN-L ; radiation belts ; electron loss ; drift loss cone
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 6381-6382 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It was predicted by us [J. Chem. Phys. 114, 4912 (2001)] that the presence of local density enhancements in a neat supercritical fluid near its liquid–vapor critical point should generate a weak anomaly in the fluid's self-diffusion constant. Herein, we examine possible reasons why the limited number of experimental studies conducted to date on diffusion constants in near-critical supercritical fluids do not provide clear evidence of this predicted weak anomaly. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 4912-4917 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: While detailed descriptions of critical anomalies are well known for thermodynamic variables, the effect of critical fluctuations on microscopic properties is much less well understood. Herein we use the results of molecular dynamics simulation, for the distribution of local densities around a tagged particle in a neat Lennard-Jones fluid, to evaluate the behavior of the self-diffusion coefficient in the critical region (Tr(approximate)1.05; 0.4〈ρr〈1.6). We find a weakly anomalous behavior at near critical densities which we attribute to both the broadening of this local-density distribution and the enhancement of mean local density. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 258-265 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose a Rayleigh-quotient-based perturbation method for estimating the least nonvanishing eigenvalue of the Fokker–Planck equation in the spatial diffusion regime. Comparison of the resulting expression against exact numerical rates in a symmetric double well produces excellent agreement at all barrier heights. The corresponding relative error is lower by more than an order of magnitude than those of existing finite-barrier expansions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 9675-9684 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an improved method for numerical evaluation of the least nonvanishing eigenvalue in dissipative systems. It is based on a modified version of the reactive flux formula for the rate which eliminates the principal shortcomings of the original formulation. A new fourth-order algorithm is used to efficiently integrate the underlying generalized Langevin equation. The proposed methodology provides accurate eigenvalues with a small computational effort for systems which could not be accurately treated with the standard techniques. Its efficiency is tested for Brownian motion in a symmetric double well subject to an exponential friction kernel. The presented results demonstrate the applicability of the method in all regimes of interest, reaching from underdamped to overdamped Brownian motion. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5251-5253 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By comparing variational transition state theory (VTST) against exact numerical calculations for the Brownian motion of a reactive particle, we uncover the unexpected result that VTST does not provide a rigorous upper bound to the least nonvanishing eigenvalue of the corresponding Fokker–Planck equation, a quantity which can be shown to correspond to the phenomenological rate constant. This result is tied to deviations between the reactive flux rate and the least nonvanishing eigenvalue which arise for intermediate to low barriers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7133-7141 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The mean relaxation time formalism introduced by Nadler and Schulten [J. Chem. Phys. 82, 151 (1985)] in their generalized moment expansion method is extended to a general diffusion process in arbitrary dimensions. The utility of the approach is demonstrated by calculating analytically the rate of noise-induced transitions in a bistable system with an isolated transition point. The rate formula obtained summarizes in a uniform manner much of what had been done before in this field. Limitations of its validity are discussed and a perturbation procedure to systematically improve it is proposed. The validity of our theoretical predictions for the rate is confirmed by comparing with exact numerical results.© 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3505-3520 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a fast, high precision and easily implementable path integral method for numerically solving Fokker–Planck equations. It is based on a generalized Trotter formula, which permits one to attain an adequate description of dynamical and equilibrium properties even though the time increment τ=t/N is rather large. A remarkable property of the symmetric Trotter splitting is used to systematically eliminate the lower-order errors resulting from time discretization. This means a significant reduction of the number of time steps that are required to retain a given accuracy for a given net increment t=Nτ, and, therefore, significantly increasing the feasibility of path integral calculations. Yet another attractive feature of the present technique is that it allows for equations with singular diffusion matrices that are known to present a special problem within the scope of the path integral formalism. The favorable scaling of the fast Fourier transform is used to numerically evaluate the path integral on a grid. High efficiency is achieved due to the Stirling interpolation which dynamically readjusts the distribution function every time step with a mild increase in cost and with no loss of precision. These developments substantially improve the path integral method and extend its applicability to various time-dependent problems which are difficult to treat by other means. One can even afford to extract information on eigenvalues and eigenfunctions from a time-dependent solution thanks to the numerical efficiency of the present technique. This is illustrated by calculating the propagator and the lowest eigenvalues of a one-dimensional Fokker–Planck equation. The method is also applied to a two-dimensional Fokker–Planck equation, whose diffusion matrix does not possess an inverse (a so-called Klein-Kramers equation). The numerical applications show our method to be a dramatic improvement over the standard matrix multiplication techniques available for evaluating path integrals in that it is much more efficient in terms of speed and storage requirements. © 1997 American Institute of Physics.
    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...