Wave packets, the Poynting vector, and energy flow: 4. Poynting and Macdonald velocities in dissipative anisotropic media (conclusion)

<p>In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth&#8217;s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm&#8217;s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.</p>

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Visualization of the energy flow for a guided forward wave in and around a fluid loaded elastic cylindrical shell: Color coding of the Poynting vector field

The Journal of the Acoustical Society of America ◽

10.1121/1.4778187 ◽

2002 ◽

Vol 111 (5) ◽

pp. 2403

Author(s):

Cleon E. Dean ◽

James P. Braselton

Keyword(s):

Cylindrical Shell ◽

Vector Field ◽

Energy Flow ◽

Poynting Vector ◽

Elastic Cylindrical Shell ◽

Forward Wave ◽

Color Coding ◽

Shell Color

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Acousto-optic devices using acoustic waves refraction

Journal of Physics Conference Series ◽

10.1088/1742-6596/2127/1/012039 ◽

2021 ◽

Vol 2127 (1) ◽

pp. 012039

Author(s):

N V Polikarpova ◽

I K Chizh

Keyword(s):

Elastic Waves ◽

Acoustic Waves ◽

Energy Flow ◽

Anisotropic Media ◽

Generation Process ◽

Practical Applications ◽

Technical Parameters ◽

Acousto Optic Device ◽

Materials Used ◽

Flow Propagation

Abstract The methods of acousto-optics provide multiple techniques for controlling optical beam. The technical parameters of corresponding acousto-optic devices are largely determined by the efficiency of acoustic waves generation. In present work we examine the features of elastic waves generation in materials used in acousto-optics. In most of practical applications the elastic wave generation process is implemented through the refraction of elastic waves at the boundary between two anisotropic media. We present a detailed study of the refraction of elastic waves in strongly anisotropic media. We report new refractive effects such as “extraordinary” refraction. In the latter case the change in the direction of the incident acoustic wave does not influence the direction of the energy flow propagation for refracted elastic waves. The configuration of an acousto-optic device using the geometry of unusual refraction in an anisotropic medium is discussed.

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Vortex energy flow in the tight focus of a non-vortex field with circular polarization

Computer Optics ◽

10.18287/2412-6179-co-582 ◽

2020 ◽

Vol 44 (1) ◽

pp. 5-11

Author(s):

V.V. Kotlyar ◽

S.S. Stafeev ◽

A.G. Nalimov

Keyword(s):

Angular Momentum ◽

Orbital Angular Momentum ◽

Energy Flow ◽

Poynting Vector ◽

Focal Spot ◽

Free Field ◽

Longitudinal Component ◽

Circularly Polarized ◽

Linearly Polarized ◽

Direct Energy

Using Richards-Wolf formulas, we show that an axisymmetric circularly polarized vortex-free field can be focused into a sharp subwavelength focal spot, around which there is a region where the light energy flow propagates along a spiral. This effect can be explained by the conversion of the spin angular momentum of the circularly polarized field into the orbital angular momentum near the focus, although the on-axis orbital angular momentum remains zero. It is also shown that a linearly polarized optical vortex with topological charge 2 forms near the focal plane an on-axis reverse energy flow (defined by the negative longitudinal component of the Poynting vector) whose amplitude is comparable with the direct energy flow.

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