scholarly journals A solution to the cosmic ray anisotropy problem

2015 ◽  
Vol 2 ◽  
pp. 51-55
Author(s):  
P. Mertsch ◽  
S. Funk
Keyword(s):  
Anisotropic Diffusion ◽  
Space Station ◽  
Cosmic Ray ◽  
Background Field ◽  
Diffusion Models ◽  
Isotropic Diffusion ◽  
Positron Fraction ◽  
Turbulent Field ◽  
Test Particles ◽  
Background Magnetic Field

Abstract. Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

scholarly journals Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

2019 ◽  
Vol 209 ◽  
pp. 01007
Author(s):  
Francesco Nozzoli
Keyword(s):  
Electron Flux ◽  
Space Station ◽  
Cosmic Ray ◽  
High Energy ◽  
Precision Measurements ◽  
High Energy Electrons ◽  
Electrons And Positrons ◽  
Positron Flux ◽  
Rigidity Dependence ◽  
Alpha Magnetic Spectrometer

Precision measurements by AMS of the fluxes of cosmic ray positrons, electrons, antiprotons, protons as well as their rations reveal several unexpected and intriguing features. The presented measurements extend the energy range of the previous observations with much increased precision. The new results show that the behavior of positron flux at around 300 GeV is consistent with a new source that produce equal amount of high energy electrons and positrons. In addition, in the absolute rigidity range 60–500 GV, the antiproton, proton, and positron fluxes are found to have nearly identical rigidity dependence and the electron flux exhibits different rigidity dependence.

Construction and testing of a Top Counting Detector and a Bottom Counting Detector for the Cosmic Ray Energetics And Mass experiment on the International Space Station

2015 ◽  
Vol 10 (07) ◽  
pp. P07018-P07018 ◽  
Author(s):  
Y.S. Hwang ◽  
H.J. Kim ◽  
T. Anderson ◽  
D. Angelaszek ◽  
M. Copley ◽  
...  
Keyword(s):  
International Space Station ◽  
Space Station ◽  
Cosmic Ray ◽  
International Space

A nonlinear anisotropic diffusion equation for image restoration with forward-backward diffusivities

2021 ◽  
Vol 14 ◽  
Author(s):  
Santosh Kumar ◽  
Nitendra Kumar ◽  
Khursheed Alam
Keyword(s):  
Image Processing ◽  
Anisotropic Diffusion ◽  
Diffusion Models ◽  
Smoothing Kernel ◽  
Proposed Model ◽  
Invariant Kernel ◽  
Nonlinear Anisotropic Diffusion ◽  
Anisotropic Diffusion Equation ◽  
Frequent Problem ◽  
Deblurring And Denoising

Background: In the image processing area, deblurring and denoising are the most challenging hurdles. The deblurring image by a spatially invariant kernel is a frequent problem in the field of image processing. Methods: For deblurring and denoising, the total variation (TV norm) and nonlinear anisotropic diffusion models are powerful tools. In this paper, nonlinear anisotropic diffusion models for image denoising and deblurring are proposed. The models are developed in the following manner: first multiplying the magnitude of the gradient in the anisotropic diffusion model, and then apply priori smoothness on the solution image by Gaussian smoothing kernel. Results: The finite difference method is used to discretize anisotropic diffusion models with forward-backward diffusivities. Conclusion: The results of the proposed model are given in terms of the improvement.

scholarly journals On the Turbulent Reduction of Drifts for Solar Energetic Particles

2021 ◽  
Vol 922 (2) ◽  
pp. 200
Author(s):  
J. P. van den Berg ◽  
N. E. Engelbrecht ◽  
N. Wijsen ◽  
R. D. Strauss
Keyword(s):  
Pitch Angle ◽  
Cosmic Ray ◽  
Energetic Particles ◽  
Solar Energetic Particles ◽  
Particle Distributions ◽  
Magnetic Turbulence ◽  
Field Diffusion ◽  
Background Magnetic Field ◽  
Perpendicular Diffusion ◽  
Inner Heliosphere

Abstract Particle drifts perpendicular to the background magnetic field have been proposed by some authors as an explanation for the very efficient perpendicular transport of solar energetic particles (SEPs). This process, however, competes with perpendicular diffusion caused by magnetic turbulence, which can also disrupt the drift patterns and reduce the magnitude of drift effects. The latter phenomenon is well known in cosmic-ray studies, but not yet considered in SEP models. Additionally, SEP models that do not include drifts, especially for electrons, use turbulent drift reduction as a justification of this omission, without critically evaluating or testing this assumption. This article presents the first theoretical step for a theory of drift suppression in SEP transport. This is done by deriving the turbulence-dependent drift reduction function with a pitch-angle dependence, as is applicable for anisotropic particle distributions, and by investigating to what extent drifts will be reduced in the inner heliosphere for realistic turbulence conditions and different pitch-angle dependencies of the perpendicular diffusion coefficient. The influence of the derived turbulent drift reduction factors on the transport of SEPs are tested, using a state-of-the-art SEP transport code, for several expressions of theoretically derived perpendicular diffusion coefficients. It is found, for realistic turbulence conditions in the inner heliosphere, that cross-field diffusion will have the largest influence on the perpendicular transport of SEPs, as opposed to particle drifts.

scholarly journals Ultra-Heavy Cosmic Ray Analysis with CALET on the International Space Station: Established and Developing Procedures

2021 ◽  
Author(s):  
Anthony Ficklin ◽  
Nicholas W Cannady ◽  
Brian Flint Rauch ◽  
Wolfgang Zober
Keyword(s):  
International Space Station ◽  
Space Station ◽  
Cosmic Ray ◽  
International Space

scholarly journals The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) Instrument

2017 ◽  
Author(s):  
Jacob Russell Smith ◽  
Y Amare ◽  
T Anderson ◽  
D Angelaszek ◽  
N Anthony ◽  
...  
Keyword(s):  
International Space Station ◽  
Space Station ◽  
Cosmic Ray ◽  
International Space

Geant4 Monte Carlo Simulations of the Galactic Cosmic Ray Radiation Environment On-Board the International Space Station/Columbus

2007 ◽  
Vol 54 (5) ◽  
pp. 1854-1862 ◽  
Author(s):  
Tore Ersmark ◽  
Per Carlson ◽  
Eamonn Daly ◽  
Christer Fuglesang ◽  
Irena Gudowska ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
International Space Station ◽  
Space Station ◽  
Cosmic Ray ◽  
Radiation Environment ◽  
International Space ◽  
Galactic Cosmic Ray

scholarly journals Observation of Properties of Primary and Secondary Cosmic Rays by the Alpha Magnetic Spectrometer on the International Space Station

2019 ◽  
Vol 208 ◽  
pp. 13002
Author(s):  
Alberto Oliva
Keyword(s):  
Cosmic Rays ◽  
International Space Station ◽  
Spectral Index ◽  
Space Station ◽  
Cosmic Ray ◽  
Magnetic Spectrometer ◽  
Light Nuclei ◽  
International Space ◽  
Rigidity Dependence ◽  
Alpha Magnetic Spectrometer

The Alpha Magnetic Spectrometer (AMS-02) is a wide acceptance high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. With a collection rate of approximately 1.7 × 1010 events/year, and the combined identification capabilities of 5 independent detectors, AMS-02 is able to precisely separate cosmic rays light nuclei (1 ≤ Z ≤ 8). Knowledge of the precise rigidity dependence of the light nuclei fluxes is important in understanding the origin, acceleration, and propagation of cosmic rays. AMS-02 collaboration has recently released the precise measurements of the fluxes of light nuclei as a function of rigidity (momentum/charge) in the range between 2 GV and 3 TV. Based on the observed spectral behaviour, the light nuclei can be separated in three distinct families: primaries (hydrogen, helium, carbon, and oxygen), secondaries (lithium, beryllium, and boron), and mixed (nitrogen). Spectral indices of all light nuclei fluxes progressively harden above 100 GV. Primary cosmic ray fluxes have an identical hardening above 60 GV, of about γ = 0.12 ± 0.04. While helium, carbon and oxygen have identical spectral index magnitude, the hydrogen spectral index shows a different magnitude, i.e. the primary-to-primary H/He ratio is well described by a single power law above 45 GV with index -0.077 ± 0.007. Secondary cosmic ray fluxes have identical rigidity dependence above 30 GV. Secondary cosmic rays all harden more than primary species, and together all secondary-to-primary ratios show a hardening difference of 0.13 ± 0.03. Remarkably, the nitrogen flux is well described over the entire rigidity range by the sum of the primary flux equal to 9% of the oxygen flux and the secondary flux equal to 62% of the boron flux.

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