scholarly journals Radiation Transfer and the Possibility of Negative Absorption in Radio Astronomy

1958 ◽  
Vol 11 (4) ◽  
pp. 564 ◽  
Author(s):  
RQ Twiss
Keyword(s):  
Kinetic Energy ◽  
Radio Astronomy ◽  
Transition Probability ◽  
Incident Radiation ◽  
High Energy ◽  
Necessary Condition ◽  
Relativistic Electrons ◽  
Radiation Process ◽  
Negative Absorption ◽  
High Energy Electrons

Stimulated transitions are relatively enormously more probable at radio than at optical frequencies and it is this which makes it possible for negative absorption to arise at radio wavelengths when the medium will behave like an amplifier to the incident radiation. A necessary condition for the existence of this phenomenon is that the kinetic energy distribution F(?) of the radiating electrons be markedly non-thermal with an appreciable excess of high energy electrons such that �F/�? is positive over a finite range of the kinetic energy ?. However, this condition is not sufficient, since it is shown that an electron gas in which free�free transitions provide the dominant radiation process can never exhibit negative absorption whatever the form of F(?), and it is further necessary that the stimulated transition probability should have a maximum at some finite value of the kinetic energy, the most favourable case occurring when this maximum is a sharp one at the value of ? at which �F/�? has a positive maximum. These conditions can both be met in principle for the cases in which the dominant radiation process is due (a) to Cerenkov effect, (b) to gyro radiation by non-relativistic electrons, (c) to synchrotron-type radiation by highly relativistic electrons, and it is shown that negative absorption can arise in all these cases; the relevance of these results to radio astronomy is discussed briefly.

Deformation of cube-textured aluminum studied using laser-induced photoelectron emission

2007 ◽  
Vol 22 (9) ◽  
pp. 2582-2589 ◽  
Author(s):  
M. Cai ◽  
S.C. Langford ◽  
J.T. Dickinson ◽  
L.E. Levine
Keyword(s):  
Kinetic Energy ◽  
Energy Distribution ◽  
Tensile Deformation ◽  
High Energy ◽  
Field Energy ◽  
Electron Backscattered Diffraction ◽  
Grain Rotation ◽  
High Energy Electrons ◽  
Low Energy Electrons ◽  
Major Surface

The evolution of the kinetic energy distribution of photoelectrons from a cube-oriented aluminum sample during tensile deformation was probed with a retarding field energy analyzer. Because of the anisotropy of the aluminum work function, the electron-energy distribution is altered as the area fractions of the major surface planes change during deformation. In cube-textured aluminum, deformation reduces the {100} area fraction and the relatively low energy electrons from these surfaces. Conversely, the {110} and {111} area fractions and the relatively high energy electrons from these surfaces both increase. These changes are quantitatively consistent with texture analysis by electron backscattered diffraction (EBSD). They reflect deformation-induced production of {111} surfaces by slip and the exposure of {110} surfaces by grain rotation. Photoelectron kinetic energy measurements supplement EBSD measurements and are readily acquired in real-time.

ADVANCES IN COHERENT BREMSSTRAHLUNG AND LPM-EFFECT STUDIES

2010 ◽  
Vol 25 (supp01) ◽  
pp. 9-33 ◽  
Author(s):  
N. F. SHUL'GA
Keyword(s):  
Short Review ◽  
High Energy ◽  
Coherent Radiation ◽  
Relativistic Electrons ◽  
Main Attention ◽  
High Energy Electrons ◽  
Electrons And Positrons ◽  
Coherent Bremsstrahlung ◽  
Radiation Processes ◽  
Amorphous Media

2008 accomplished the 100th anniversary from the birth of L.D. Landau (Nobel Prize 1962). In the paper a short description of Kharkov period of Landau's work from 1932 to 1937 is given. One of areas of his work is connected with investigation of bremsstrahlung by ultra relativistic electrons in matter. In this paper a short review of the results obtained studying both Landau-Pomeranchuk-Migdal effect and coherent radiation by high-energy electrons and positrons in crystals, is given. The main attention is paid to the general properties and difference of radiation processes in amorphous media and in a crystal and to advances in the coherent bremsstrahlung studies.

Energy loss of relativistic electrons in plasma in accordance with covariant Fokker–Planck formalism

1980 ◽  
Vol 24 (1) ◽  
pp. 75-88 ◽  
Author(s):  
P. S. Ray
Keyword(s):  
Energy Loss ◽  
Green's Function ◽  
High Energy ◽  
Stopping Power ◽  
Function Technique ◽  
Relativistic Electrons ◽  
Relativistic Generalization ◽  
Ion Scattering ◽  
High Energy Electrons ◽  
Fokker Planck

A relativistic generalization of the Fokker–Planck formalism has been constructed. This is applied to the study of energy loss of high-energy electrons in plasma. Both the electron–electron and electron–ion scattering have been considered in a relativistic way. The expression obtained for the stopping power differs from that derived with the help of thermodynamic Green's function technique.

scholarly journals Terrestrial Radio Signals May Suppress High-Energy Electrons

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Morgan Rehnberg
Keyword(s):  
Geomagnetic Storms ◽  
High Energy ◽  
Relativistic Electrons ◽  
High Energy Electrons ◽  
Radio Signals

Naval radio signals may cause the formation of a barrier observed during geomagnetic storms that is seemingly impenetrable by relativistic electrons.

scholarly journals Non-Thermal Activity and Particle Acceleration in Clusters of Galaxies

2005 ◽  
Vol 13 ◽  
pp. 317-321
Author(s):  
Vahe’ Petrosian
Keyword(s):  
Galactic Nuclei ◽  
High Energy ◽  
Relativistic Electrons ◽  
Thermal Activity ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
High Energy Electrons ◽  
Inverse Compton

AbstractEvidence for non-thermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons, and new windows (in EUV and Hard X-ray ranges) have provided more powerful tools for its investigation. The hard X-ray observations, notably from Coma, are summarized and results of a new RXTE observations of a high red-shift cluster are presented. It is shown that the most likely emission mechanism for these radiations is the inverse Compton scattering of the cosmic microwave background photons by the same electrons responsible for the radio radiation. Various scenarios for acceleration of the electrons are considered and it is shown that the most likely model is episodic acceleration by shocks or turbulence, presumably induced by merger activity, of high energy electrons injected into the inter-cluster medium by galaxies or active galactic nuclei.

COOLING OF RELATIVISTIC ELECTRONS IN TEV BLAZARS: CLUES FROM MULTIWAVELENGTH SPECTRA

2008 ◽  
Vol 17 (09) ◽  
pp. 1591-1601
Author(s):  
R. SCHLICKEISER
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Kinetic Energy ◽  
High Energy ◽  
Particle Energy ◽  
Field Energy ◽  
Kinetic Energy Density ◽  
Relativistic Electrons ◽  
Magnetic Field Energy ◽  
The Magnetic Field

In powerful cosmic nonthermal radiation sources with dominant magnetic-field self generation, the generation of magnetic fields at almost equipartition strength by relativistic plasma instabilities operates as fast as the acceleration or injection of ultra-high energy radiating electrons and hadrons in these sources. Consequently, the magnetic field strength becomes time-dependent and adjusts itself to the actual kinetic energy density of the radiating electrons in these sources. This coupling of the magnetic field and the magnetic field energy density to the kinetic energy of the radiating particles changes both the intrinsic temporal evolution of the relativistic particle energy spectrum after injection and the synchrotron and synchrotron self-Compton emissivities.

scholarly journals Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

2019 ◽  
Vol 209 ◽  
pp. 01007
Author(s):  
Francesco Nozzoli
Keyword(s):  
Electron Flux ◽  
Space Station ◽  
Cosmic Ray ◽  
High Energy ◽  
Precision Measurements ◽  
High Energy Electrons ◽  
Electrons And Positrons ◽  
Positron Flux ◽  
Rigidity Dependence ◽  
Alpha Magnetic Spectrometer

Precision measurements by AMS of the fluxes of cosmic ray positrons, electrons, antiprotons, protons as well as their rations reveal several unexpected and intriguing features. The presented measurements extend the energy range of the previous observations with much increased precision. The new results show that the behavior of positron flux at around 300 GeV is consistent with a new source that produce equal amount of high energy electrons and positrons. In addition, in the absolute rigidity range 60–500 GV, the antiproton, proton, and positron fluxes are found to have nearly identical rigidity dependence and the electron flux exhibits different rigidity dependence.

scholarly journals Polar Middle Atmospheric Responses to Medium Energy Electron (MEE) Precipitation Using Numerical Model Simulations

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 133
Author(s):  
Ji-Hee Lee ◽  
Geonhwa Jee ◽  
Young-Sil Kwak ◽  
Heejin Hwang ◽  
Annika Seppälä ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Meridional Circulation ◽  
Stratospheric Ozone ◽  
High Energy ◽  
Chemical Changes ◽  
Temperature Changes ◽  
Mesospheric Temperature ◽  
High Energy Electrons ◽  
Circulation Changes

Energetic particle precipitation (EPP) is known to be an important source of chemical changes in the polar middle atmosphere in winter. Recent modeling studies further suggest that chemical changes induced by EPP can also cause dynamic changes in the middle atmosphere. In this study, we investigated the atmospheric responses to the precipitation of medium-to-high energy electrons (MEEs) over the period 2005–2013 using the Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Our results show that the MEE precipitation significantly increases the amounts of NOx and HOx, resulting in mesospheric and stratospheric ozone losses by up to 60% and 25% respectively during polar winter. The MEE-induced ozone loss generally increases the temperature in the lower mesosphere but decreases the temperature in the upper mesosphere with large year-to-year variability, not only by radiative effects but also by adiabatic effects. The adiabatic effects by meridional circulation changes may be dominant for the mesospheric temperature changes. In particular, the meridional circulation changes occasionally act in opposite ways to vary the temperature in terms of height variations, especially at around the solar minimum period with low geomagnetic activity, which cancels out the temperature changes to make the average small in the polar mesosphere for the 9-year period.

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