scholarly journals Interstellar Scattering: Observations and Interpretations

1996 ◽  
Vol 160 ◽  
pp. 439-446
Author(s):  
Barney Rickett
Keyword(s):  
Radio Propagation ◽  
Density Spectrum ◽  
Kolmogorov Model ◽  
Successful Theory ◽  
Interstellar Plasma ◽  
Interstellar Scattering ◽  
Warm Ionized Medium ◽  
Turbulent Cascade

AbstractThe successful theory for radio propagation through the interstellar plasma is reviewed, where the density spectrum follows the Kolmogorov model. However, there are also several observations indicating more refraction than expected. A particular model of enhanced refraction is proposed in which isolated regions of the warm ionized medium support filaments of enhanced density on a scale of 1 AU, which do not couple to a turbulent cascade.

scholarly journals Speckles in Interstellar Radio-Wave Scattering

1991 ◽  
Vol 131 ◽  
pp. 238-241
Author(s):  
K. M. Desai ◽  
C. R. Gwinn ◽  
J. Reynolds ◽  
E. A. King ◽  
D. Jauncey ◽  
...  
Keyword(s):  
Radio Source ◽  
Radio Wave ◽  
Wave Scattering ◽  
Speckle Pattern ◽  
Complete Information ◽  
Radio Waves ◽  
Interstellar Plasma ◽  
Interstellar Scattering ◽  
Vela Pulsar ◽  
Scattering Material

AbstractObservations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales (≈seconds) and narrow bandwidths (≈kHz). Here, we present first observations, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.

scholarly journals The Influence of Propagation through the Irregular Interstellar Plasma on VLBI Observations

1988 ◽  
Vol 129 ◽  
pp. 287-294
Author(s):  
B.J. Rickett ◽  
W.A. Coles
Keyword(s):  
Interstellar Medium ◽  
Radio Sources ◽  
Vlbi Observations ◽  
Interstellar Plasma ◽  
Interstellar Scattering ◽  
Galactic Sources

It has been known since pulsars were discovered that the interstellar medium (ISM) can cause angular broadening of radio sources. However, the amount of scattering along typical lines of sight to extra-galactic sources is not large enough to cause any loss of visibility, even on intercontinental baselines, unless the frequency is below about 100 MHz. Recent studies have shown that interstellar scattering (ISS) can have considerably stronger effects; this paper addresses their relevance to VLBI.

scholarly journals Studying Pulsar Emission Regions Using Interstellar Scattering

2001 ◽  
Vol 182 ◽  
pp. 65-70
Author(s):  
Carl R. Gwinn
Keyword(s):  
Radio Wave ◽  
Wave Scattering ◽  
Diffraction Limit ◽  
Pulsar Emission ◽  
The Past ◽  
Interstellar Plasma ◽  
Interstellar Scattering

AbstractRadio-wave scattering in the interstellar plasma provides the means to circumvent the diffraction limit for earth-based instruments, and to image the emission regions of pulsars. For the past 25 years, observers have sought to exploit this fact to learn how pulsars shine. I review the techniques developed, and summarize measurements of size of emission regions of pulsars to date.

scholarly journals Limits on Refractive Interstellar Scattering of H2O Masers

1988 ◽  
Vol 129 ◽  
pp. 295-296
Author(s):  
C. R. Gwinn ◽  
J. M. Moran ◽  
M. J. Reid ◽  
M. H. Schneps
Keyword(s):  
Spectral Index ◽  
Power Law ◽  
Constant Velocity ◽  
Large Scale ◽  
Density Fluctuations ◽  
Small Scale ◽  
Interstellar Plasma ◽  
Interstellar Scattering

We limit the spectral index of density fluctuations in the interstellar plasma by comparing maser sizes, due to small-scale fluctuations, with wander of masers from constant velocity, possibly due to refraction by large-scale fluctuations. The wander of the masers about constantvelocity motion limits power-law spectra of the fluctuations to indices less than 4.0.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

Dependence of the Properties of a Turbulent Cascade behind the Bow Shock on the Dynamics of the Solar Wind Parameters

2020 ◽  
Vol 58 (6) ◽  
pp. 478-486
Author(s):  
L. S. Rakhmanova ◽  
M. O. Riazantseva ◽  
G. N. Zastenker ◽  
Yu. I. Yermolaev ◽  
I. G. Lodkina
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Solar Wind Parameters ◽  
Turbulent Cascade
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