Cosmic Ray Distribution Function Research Articles

Time variations of the cosmic ray distribution function during a solar proton event of September 29, 1989

On the basis of cosmic ray (CR) ground‐based observations from the world stations network during the solar proton event of September 29, 1989, the method of spectrographic global survey was used to investigate variations of the particle distribution function in the rigidity range from a few to tens of gigavolts. By analyzing results obtained on variations of the angular distribution of different‐energy particles and time profiles of CR intensity, it is concluded that it is impossible to describe the process of solar CR propagation in terms of the simplest ideas of the motion of particles in the outer electromagnetic fields of the heliosphere. To explain the results obtained, it is speculated that a particle beam accelerated in the flare propagates along the heliospheric current sheet, as a result of which in interplanetary space polarization electric fields are produced, through which an energy exchange occurs between solar CR and background particles of solar wind plasma and galactic CR.

The influence of intermediate‐scale variations in the heliospheric magnetic field on the transport of galactic cosmic rays

Variations in the heliospheric magnetic field occur on most scales including those lying intermediate between the gyro‐radii of galactic cosmic rays and heliocentric radial distance. It is demonstrated that a correlation exists between these intermediate‐scale variations in the magnetic field and the variations in the cosmic ray distribution function that result from the field variations. This correlation will affect the average transport of galactic cosmic rays by significantly altering the patterns of gradient and curvature drifts in the heliosphere. During the current solar cycle, the altered drift patterns can lead to larger radial gradients of the galactic cosmic rays and significantly smaller latitude gradients than is expected only from drifts in the mean magnetic field.

Galactic cosmic-ray mediation of a spherical solar wind flow. 1: The steady state cold gas hydrodynamical approximation

view Abstract Citations (8) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galactic Cosmic-Ray Mediation of a Spherical Solar Wind Flow. I. The Steady State Cold Gas Hydrodynamical Approximation Le Roux, J. A. ; Ptuskin, V. S. Abstract Realistic models of the outer heliosphere should consider that the interstellar cosmic-ray pressure becomes comparable to pressures in the solar wind at distances more than 100 AU from the Sun. The cosmic-ray pressure dynamically affects solar wind flow through deceleration. This effect, which occurs over a scale length of the order of the effective diffusion length at large radial distances, has important implications for cosmic-ray modulation and acceleration. As a first step toward solution of this nonlinear problem, a steady state numerical model was developed for a relatively cold spherical solar wind flow which encounters the confining isotropic pressure of the surrounding Galactic medium. This pressure is assumed to be dominated by energetic particles (Galactic cosmic rays). The system of equations, which are solved self-consistently, includes the relevant hydrodynamical equations for the solar wind flow and the spherical cosmic-ray transport equation. To avoid the closure parameter problem of the two-fluid model, the latter equation is solved for the energy-dependent cosmic-ray distribution function. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175086 Bibcode: 1995ApJ...438..427L Keywords: Astronomical Models; Cold Gas; Galactic Cosmic Rays; Hydrodynamics; Solar Wind; Steady State; Cosmology; Deceleration; Heliosphere; Mathematical Models; Radiation Pressure; Space Radiation; ACCELERATION OF PARTICLES; HYDRODYNAMICS; ISM: COSMIC RAYS; SUN: SOLAR WIND full text sources ADS | Related Materials (1) Part 2: 1995ApJ...452..423L

Cosmic ray scintillations in random magnetic fields with non-zero helicity

The cosmic ray scintillation theory is modified for the case of non diagonal IMF correlation tensor. We introduce the term ‘helicity of cosmic ray scintillation’. It describes rotation of the cosmic ray distribution function.

The use of cosmic rays for continuous monitoring and prediction of some dangerous phenomena for the earth's civilization

The main idea of the International Cosmic Ray Service (ICRS) is to combine satellite and spaceprobe cosmic rays, magnetic and plasma data with groundbased cosmic ray data (exchanged in real time) for obtaining continuous information on the electromagnetic and radiation situation in the interplanetary space and Earth's magnetosphere: prediction of great geomagnetic storms, big increases of radiation hazards and other dangerous phenomena in space and on the Earth for people and technology. ICRS can predict not only geomagnetic storms and unfavorable days in the environment (especially important for old people and people with some diseases), but, in combination with astrophysical methods, can predict big increases of radiation hazards very dangerous for the Earth's civilization and big changes in the environment due to extremely powerful solar flares and local supernova explosions. We hope that, after some additional investigation of high energy cosmic-ray distribution function outside the heliosphere, it could be possible to solve by ICRS more complicated problems: to determine in combination with astrophysical methods the location and velocity of nearest dust-molecular galactic clouds with frozen-in magnetic fields and predict the expected time of the Sun capturing by some clouds with possible changes of Earth's global climate. The foundation of ICRS could bring a new possibility of development to the cosmic ray observatories, release scientists from a lot of routine work and increase the fundamental and applied research efficiency.

Viscosity and inertia in cosmic-ray transport - Effects of an average magnetic field

view Abstract Citations (22) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Viscosity and Inertia in Cosmic-Ray Transport: Effects of an Average Magnetic Field Williams, L. L. ; Jokipii, J. R. Abstract A generalized transport equation is introduced which describes the transport and propagation of cosmic rays in a magnetized, collisionless medium. The equation is valid if the cosmic-ray distribution function is nearly isotropic in momentum, if the ratio of fluid speed to fluid-flow particle speed is small, and if the ratio of collision time to time for change in the macroscopic flow is small. Five independent cosmic-ray viscosity coefficients are found, and the ralationship of this viscosity to particle orbits in a magnetic field is presented. Publication: The Astrophysical Journal Pub Date: April 1991 DOI: 10.1086/169930 Bibcode: 1991ApJ...371..639W Keywords: Cosmic Rays; Magnetohydrodynamic Waves; Particle Acceleration; Radiation Transport; Wave Propagation; Anisotropy; Background Radiation; Magnetic Fields; Polarization (Waves); Viscous Fluids; Space Radiation; COSMIC RAYS: GENERAL; HYDROMAGNETICS; PARTICLE ACCELERATION; WAVE MOTIONS full text sources ADS |

Cosmic-ray fluctuations in interplanetary space

Cosmic-ray (CR) fluctuations in both the drift and diffusion approximations are investigated and the results compared with experimental data. Kinetic equation is used to obtain equations for the second moment of the CR distribution function (the correlation function of the distribution function fluctuations) in both approximations. An application of these approximations to the correlation function equation gives the relations between the CR power spectra and random magnetic fields in interplanetary space. Different magneto-turbulence models are taken in consideration and the relations between the spectral indices are obtained in various frequency intervals.

Cosmic-ray streaming perpendicular to the mean magnetic field

The distribution function of cosmic rays streaming perpendicular to the mean magnetic field in a turbulent medium is re-examined. Urch's (1977) discovery that, in quasilinear theory, the flux is due to particles at 90° pitch angle is discussed and shown to be consistent with previous formulations of the theory. We point out that this flux of particles at 90° cannot be arbitrarily set equal to zero, and hence we dismiss the alternative theory which proceeds from this premise. A further, basic inconsistency in Urch's new transport equation is demonstrated, and the connection between quasilinear theory and compound diffusion is discussed.

Cosmic ray kinetics in space

This work gives a systematic description of the statistical theory of the propagation of cosmic ray charged particles through random electromagnetic fields in space. A kinetic equation is derived for the cosmic ray distribution function averaged over the statistical ensemble corresponding to a random field. Transition to the diffusion approximation is considered, and the problems of the scattering and acceleration of charged particles are analyzed. The theory of fluctuation effects in cosmic rays is briefly discussed.

On the interplanetary cosmic-ray scintillations

The equation for the two-particles cosmic-ray distribution function is derived by means of the Boltzmann kinetic equation averaging. This equation is valid for arbitrary ratio of regular and random parts of the magnetic field. For small energy particles the guiding-center approximation is used. On the basis of the derived equation the dependence between power spectra of cosmic-ray intensity and random magnetic field is obtained. If power spectra are degree functions for high energy particles (≈ 10 GeV nucleon−1), then the spectral exponent υ of magnetic field lies between ϱ and ϱ−2, where ϱ is the spectral exponent of cosmic-ray power spectra. The experimental data concerning moderate energy particles are in accordance with υ=ϱ, which demonstrates that the magnetic fluctuations are isotropic or cosmic-ray space gradient is small near the Earth orbit.

Fokker-Planck theory for cosmic ray diffusion in the presence of Alfvén waves 1. Theory

Using the standard quasi-linear Fokker-Planck approach and an expansion of the cosmic ray distribution function in Legendre polynomials, we derive a complete set of Fokker-Planck coefficients and expressions for the complete cosmic ray diffusion tensor due to linearly polarized planar Alfven waves propagating at an angle to the average magnetic field. We find that although an off-diagonal term formally appears in the diffusion tensor, it is identically zero. In addition, the cross-field diffusion coefficient is identically the same as that found for wave propagation exactly parallel to the average magnetic field.

Cosmic Rays in a Random Magnetic Field: Breakdown of the Quasilinear Derivation of the Kinetic Equation

The problem of deriving a kinetic equation for the cosmic ray distribution function in a random magnetic field is considered. A model is adopted which is mathematically simple but which contains the essential physics. The perturbation expansion upon which the quasi-linear treatment is based is investigated. The existence of resonant particles causes the breakdown of the adiabatic approximation frequently used in this theory. Resonant particles cause a general secular growth of higher order terms in the expansion which invalidates the entire perturbative approach.

The Propagation and Anisotropy of Cosmic Rays. I. Theory for Steady Streaming

view Abstract Citations (105) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Propagation and Anisotropy of Cosmic Rays. I. Theory for Steady Streaming Wentzel, Donat G. Abstract We consider cosmic rays steadily streaming along a uniform magnetic field and down a cosmic-ray density gradient. The anisotropy generates hydromagnetic waves which, in turn, scatter the cosmic rays. We derive both the shape of the cosmic-ray distribution function and the wave spectrum for a steady state with a low cosmic-ray streaming velocity. The results are summarized in § VI. Limits of validity are discussed in terms of a numerical example Publication: The Astrophysical Journal Pub Date: April 1969 DOI: 10.1086/149965 Bibcode: 1969ApJ...156..303W full text sources ADS | Related Materials (1) Part 2: 1969ApJ...157..545W