455 research outputs found
On the flow of a magnetized solar wind around the moon
Effects of interplanetary magnetic fields on flow of plasma around moo
Diffusion and convection of energetic electrons behind the earth's bow shock
Diffusion effects on energy spectrum of electron group analyzed during downwind convection in bow shock transition region of eart
Cosmic-ray transport theory and out-of-the-ecliptic exploration
The reasons for studying cosmic-ray transport theory are summarized and the fundamentally three-dimensional nature of the process is pointed out. It is shown that observations in the solar ecliptic plane cannot unambiguously test transport theories since the solutions to the transport equations depend critically on boundary conditions and variation of parameters such as diffusion tensor out of the ecliptic. Sample calculations (Fokker-Planck coefficient) are shown which illustrate the problem. It is concluded that out-of-the-ecliptic observations are essential to further test transport theory
On the transport of charged particles in turbulent fields: comparison of an exact solution with the quasilinear approximation
The problem of charged-particle transport in a magnetic field which is solely a function of time is solved. The solution is obtained exactly, to all orders in the field, in the limit of large wavelengths normal to the magnetic field. It is shown that the usual quasilinear, Fokker-Planck approximation is equal to the exact solution in the limit of times large compared with the correlation time of the fluctuating field. This is just the regime where the approximation has been used in the past, and this special case thus gives some support to the standard approximation techniques
Effects of a wavy neutral sheet on cosmic ray anisotropies
The first results of a three-dimensional numerical code calculating cosmic ray anisotropies is presented. The code includes diffusion, convection, adiabatic cooling, and drift in an interplanetary magnetic field model containing a wavy neutral sheet. The 3-D model can reproduce all the principal observations for a reasonable set of parameters
A Two-Dimensional, Self-Consistent Model of Galactic Cosmic Rays in the Heliosphere
We present initial results from our new two-dimensional (radius and
latitude), self-consistent model of galactic cosmic rays in the heliosphere. We
focus on the latitudinal variations in the solar wind flow caused by the
energetic particles. Among other things our results show that the cosmic rays
significantly modify the latitudinal structure of the solar wind flow
downstream of the termination shock. Specifically, for A>0 (corresponding to
the present solar minimum) the wind beyond the shock is driven towards the
equator, resulting in a faster wind flow near the current sheet, while for A<0
the effect is reversed and the wind turns towards the pole, with a faster flow
at high latitudes. We attribute this effect to the latitudinal gradients in the
cosmic ray pressure, caused by drifts, that squeeze the flow towards the
ecliptic plane or the pole, respectively.Comment: 10 pages, 4 Postscript figures, uses AAS LaTeX v4.0, to be published
in The Astrophysical Journal Letter
Wavelength dependence of the interplanetary scintillation index
Published observations of the interplanetary scintillation index m sub z are shown to vary with wavelength in a manner consistent with a smooth, power law spectrum of plasma fluctuations. This is in contrast to recent work arguing that the data require a spectrum with two separate regimes. It is concluded that published observations of m sub z are consistent with either type of density spectrum
Numerical Descriptions of Cosmic-Ray Transport
The behavior of energetic particles in the solar system is described by a well known Fokker-Planck equation. Although analytic methods yield insight into the nature of its solutions, especially in the diffusion regime, calculations that go beyond diffusion are very complicated. The reliability of these calculations is of concern, because numerical methods are notorious for their errors and artifacts. The well known Milne problem of classical transport theory was analyzed with the aid of three different numerical methods. These are: (1) The method of eigenfunctions in which the distribution function is approximated by a sum of eigenfunctions of the scattering operator, (2) Numerical solutions of a finite difference aquation; and (3) Direct simulation of the scattering and streaming of individual particles with the aid of Monte Carlo methods
Acceleration of Electrons near the Earth's Bow Shock
Accleration mechanism of electron plasma outside magnetosphere near bow shock regio
A numerical study of diffusive shock acceleration of cosmic rays in supernova shocks
The evolution of the energy spectrum of cosmic rays accelerated by the first order Fermi mechanism, by a supernova remnant shock wave, including adiabatic deceleration effects behind the front, is carried out by means of a time-dependent numerical code. The calculations apply to the adiabatic stage (or Sedov stage) of the supernova explosion, and the energetic particle spectrum is calculated in the test particle limit (i.e., the back reaction of the cosmic rays on the flow is not included). The particles are injected mono-energetically at the shock. The radial distribution, The radial distribution, and the spectrum of the accelerated and decelerated particles is shown
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