Speckles in Interstellar Radio-Wave Scattering

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.

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Studying Pulsar Emission Regions Using Interstellar Scattering

International Astronomical Union Colloquium ◽

10.1017/s0252921100000713 ◽

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.

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Anomalous Radio‐Wave Scattering from Interstellar Plasma Structures

The Astrophysical Journal ◽

10.1086/319442 ◽

2001 ◽

Vol 549 (2) ◽

pp. 997-1010 ◽

Cited By ~ 68

Author(s):

J. M. Cordes ◽

T. Joseph W. Lazio

Keyword(s):

Radio Wave ◽

Wave Scattering ◽

Interstellar Plasma

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Anisotropic radio-wave scattering from englacial water regimes, Mýrdalsjökull, Iceland

Journal of Glaciology ◽

10.3189/002214307783258422 ◽

2007 ◽

Vol 53 (182) ◽

pp. 473-478 ◽

Cited By ~ 11

Author(s):

Kenichi Matsuoka ◽

Throstur Thorsteinsson ◽

Helgi Björnsson ◽

Edwin D. Waddington

Keyword(s):

Radio Wave ◽

Wave Scattering ◽

Flow Direction ◽

Low Frequency ◽

Radio Waves ◽

Glacier Surface ◽

Ice Flow ◽

Scattering Model ◽

Water Regimes ◽

Strong Scattering

AbstractColinear-polarized 5 MHz radar profiling data were obtained on Mýrdalsjökull, a temperate glacier in Iceland. Radar transects, and therefore polarization planes, were aligned approximately parallel, transverse and oblique to the ice flow direction. Echoes from the shallower half to two-thirds of the ice were 10–20dB stronger on the oblique and longitudinal transects than those on the transverse transects. Anisotropy as a function of depth is clearly seen at the sites where the transects cross. Strong scattering on longitudinal transects apparently caused extinction of a radar-reflecting layer that was continuously profiled on the transverse transects. A radio-wave scattering model shows that scattering from a longitudinal water-filled conduit parallel to the glacier surface can explain the observed azimuthal variations of the echo. We conclude that low-frequency (~MHz) radio waves can help to characterize englacial water regimes.

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LOFAR observations of radio burst source sizes and scattering in the solar corona

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038518 ◽

2020 ◽

Vol 645 ◽

pp. A11

Author(s):

Pearse C. Murphy ◽

Eoin P. Carley ◽

Aoife Maria Ryan ◽

Pietro Zucca ◽

Peter T. Gallagher

Keyword(s):

Solar Corona ◽

Radio Source ◽

Radio Wave ◽

Radio Burst ◽

Wave Scattering ◽

Low Frequency ◽

Density Fluctuations ◽

Source Size ◽

Burst Source ◽

Low Frequencies

Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR’s point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be 18.8′ ± 0.1′ and 10.2′ ± 0.1′, respectively, at a plane of sky heliocentric distance of 1.75 R⊙. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of ε may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images.

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An AU-Aperture Lens to Resolve the Vela Pulsar’s Radio Emission Region

International Astronomical Union Colloquium ◽

10.1017/s0252921100042093 ◽

1996 ◽

Vol 160 ◽

pp. 459-461

Author(s):

C.R. Gwinn ◽

M.J. Ojeda ◽

M.C. Britton ◽

J.E. Reynolds ◽

D.L. Jauncey ◽

...

Keyword(s):

Radio Emission ◽

Radio Wave ◽

Wave Scattering ◽

Supernova Remnant ◽

Emission Region ◽

Vela Pulsar

AbstractWe use radio-wave scattering in the Vela supernova remnant, surrounding the Vela pulsar, as an AU-scale lens to study the Vela pulsar’s emission region.

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Sensing Framework for the Internet of Actors in the Value Co-Creation Process with a Beacon-Attachable Indoor Positioning System

Sensors ◽

10.3390/s21010083 ◽

2020 ◽

Vol 21 (1) ◽

pp. 83

Author(s):

Keiichi Zempo ◽

Taiga Arai ◽

Takuya Aoki ◽

Yukihiko Okada

Keyword(s):

Radio Wave ◽

Indoor Positioning ◽

Measurement Range ◽

Pulse Interval ◽

Retail Stores ◽

Positioning System ◽

Radio Waves ◽

Positioning Systems ◽

Environment Recognition ◽

Indoor Positioning System

To evaluate and improve the value of a service, it is important to measure not only the outcomes, but also the process of the service. Value co-creation (VCC) is not limited to outcomes, especially in interpersonal services based on interactions between actors. In this paper, a sensing framework for a VCC process in retail stores is proposed by improving an environment recognition based indoor positioning system with high positioning performance in a metal shelf environment. The conventional indoor positioning systems use radio waves; therefore, errors are caused by reflection, absorption, and interference from metal shelves. An improvement in positioning performance was achieved in the proposed method by using an IR (infrared) slit and IR light, which avoids such errors. The system was designed to recognize many and unspecified people based on the environment recognition method that the receivers had installed, in the service environment. In addition, sensor networking was also conducted by adding a function to transmit payload and identification simultaneously to the beacons that were attached to positioning objects. The effectiveness of the proposed method was verified by installing it not only in an experimental environment with ideal conditions, but posteriorly, the system was tested in real conditions, in a retail store. In our experimental setup, in a comparison with equal element numbers, positioning identification was possible within an error of 96.2 mm in a static environment in contrast to the radio wave based method where an average positioning error of approximately 648 mm was measured using the radio wave based method (Bluetooth low-energy fingerprinting technique). Moreover, when multiple beacons were used simultaneously in our system within the measurement range of one receiver, the appropriate setting of the pulse interval and jitter rate was implemented by simulation. Additionally, it was confirmed that, in a real scenario, it is possible to measure the changes in movement and positional relationships between people. This result shows the feasibility of measuring and evaluating the VCC process in retail stores, although it was difficult to measure the interaction between actors.

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