Journal ArticleDOI
Dynamic spectra of interplanetary scintillations
William A. Coles,J. P. Filice +1 more
Reads0
Chats0
TLDR
In this paper, the authors compare the observations with a numerical simulation of the diffraction of plane waves by a two-dimensional random phase screen and show good qualitative agreement with the observations when the turbulence spectrum in the phase screen is a simple power law with the Kolmogorov exponent.Abstract:
Interplanetary scintillations (IPS) are fluctuations in the apparent intensity of radio sources caused by fluctuations in the electron density of the solar wind1. Observations at a single wavelength provide information on the spatial spectrum of electron density at scales of the order of the radius of the first Fresnel zone. However, dynamic spectra covering a wide range of wavelengths show evidence of fluctuations on a much larger scale2. Unfortunately, the problem of estimation of the spatial spectrum at this larger scale is analytically intractable. Here we compare the observations2 with a numerical simulation of the diffraction of plane waves by a two-dimensional random phase screen. The frequency–time structure of the simulated IPS shows good qualitative agreement with the observations when the turbulence spectrum in the phase screen is a simple power law with the Kolmogorov exponent. No ad hoc large-scale structure is necessary to account for the observations.read more
Citations
More filters
Journal ArticleDOI
Simulation of laser propagation in a turbulent atmosphere
TL;DR: The split-step Fourier-transform algorithm for numerical simulation of wave propagation in a turbulent atmosphere is refined to correctly include the effects of large-scale phase fluctuations that are important for imaging problems and many beam-wave problems such as focused laser beams and beam spreading.
Journal ArticleDOI
Simulation of wave propagation in three-dimensional random media
TL;DR: Quantitative error analyses for the simulation of wave propagation in three-dimensional random media, when narrow angular scattering is assumed, are presented for plane-wave and spherical-wave geometry.
Journal ArticleDOI
The solar wind density spectrum near the Sun: Results from Voyager radio measurements
TL;DR: In this article, radio propagation data from the Voyager 1 and Voyager 2 spacecrafts were analyzed to yield the wave structure function, a statistic which is related to, but obtained more readily than, the spectrum itself.
Journal ArticleDOI
Scattering of Pulsar Radio Emission by the Interstellar Plasma
William A. Coles,William A. Coles,Barney Rickett,J. J. Gao,George Hobbs,Joris P. W. Verbiest,Joris P. W. Verbiest +6 more
TL;DR: In this paper, the authors present simulations of scattering phenomena which are important in pulsar observations, but which are analytically intractable, and demonstrate the effect of analyzing observations which are shorter than the refractive scale.
Journal ArticleDOI
The distribution of Met-enkephalin like immunoreactivity in the brain of Apteronotus leptorhynchus, with emphasis on the electrosensory system
Stephanie Richards,Leonard Maler +1 more
TL;DR: The distribution of immunoreactive fibers in the brain of this gymnotiform fish indicates that Met-enkephalin may be generally involved in theregulation of sensory, neuroendocrine and reproductive functions and specifically in the regulation of electrocommunication.
References
More filters
Journal ArticleDOI
Interplanetary Scintillation of Small Diameter Radio Sources
TL;DR: In this article, the authors used the black-body equations to calculate the increased radiation appropriate to the observed brightness increase in the star over a 1,000 A.u. band-width at 5,400 A.U.
Journal ArticleDOI
Scintillations due to a concentrated layer with a power‐law turbulence spectrum
TL;DR: In this article, the spectrum of refractive index fluctuations is taken to be an unmodified power law of arbitrary strength, with exponent α, 2 30, it represents essentially all of the intensity fluctuations and shows that m saturates at unity for a plane wave as U → ∞.
Journal ArticleDOI
Computed scintillation spectra for strong turbulence
TL;DR: In this paper, a power law spectrum with index α = 3 was assumed for the turbulence or refractive index spectrum, and the intensity spectra were found to duplicate the Born approximation for weak scattering and the high frequency approximation for strong scattering.