In an absorbing medium, where the vector W5]v/]k usually is complex for real values of the wave vector k, the group velocity W may become real for some complex values of k. The role of real group velocity in the propagation of one-dimensional wave packets in homogeneous absorbing media is examined. Applying the saddle point method to an analysis of the asymptotic behavior of the Gaussian wave p...

Radiation of electromagnetic waves by a uniformly moving charge is the subject of extensive research over the last several decades. Fascinating effects such as Vavilov-Cherenkov radiation, transition radiation and the Smith-Purcell effect were discovered and studied in depth. In this letter we study the radiation of a line charge moving with relativistic constant velocity within an average zero...

Space Weather is the study of the conditions in the solar wind that can affect life on the surface of the Earth, particularly the increasingly technologically sophisticated devices that are part of modern life. Solar radio observations are relevant to such phenomena because they generally originate as events in the solar atmosphere, including flares, coronal mass ejections and shocks, that prod...

Parametric instabilities driven by partially coherent radiation in plasmas are described by a generalized statistical Wigner-Moyal set of equations, formally equivalent to the full wave equation, coupled to the plasma fluid equations. A generalized dispersion relation for stimulated Raman scattering driven by a partially coherent pump field is derived, revealing a growth rate dependence, with t...

Periodic multilayers give rise to enhanced X-ray fluorescence when a regime of standing waves occurs within the structure. This regime may concern the primary radiation used to induce the fluorescence, the secondary radiation of fluorescence or both of them. Until now, existing models only dealt with standing wave regime of primary radiation. We present a theoretical approach based on the oscil...

The measurement of microwave radiation has been widely used in atmospheric remote sensing, such as temperature profiling, and vapor and liquid column measurements [1] [5]. The radiation from atmosphere is due to the absorption (emission) and scattering of electromagnetic (EM) wave by atmospheric particles (gaseous molecules, liquid water droplets and ice crystals). The absorption directly contr...

Light of wave lengths 0.30micro to 0.50micro, accelerates return of the cleavage rate of Arbacia eggs to normal, after delay by exposure to ultraviolet radiation (wave lengths 0.238micro to 0.31micro). Recovery is apparently complete. Wave lengths 0.30micro to 0.50micro have no effect on the cleavage rate of normal eggs, nor does such illumination previous to dosage with ultraviolet radiation i...

In the plasma beat wave acceleration scheme, the ponderomotive force of a two-frequency laser pulse resonantly drives a large amplitude (E≈3 GV/m) relativistic electrostatic plasma wave. The electro-static (es) wave does not couple to the vacuum modes and its energy is dissipated in the plasma. With a static magnetic field B0z applied perpendicularly to the laser beam propagation axis x, the tw...

A novel MEMS thermopile structure is presented, which consist of linearly arranged pand ntype polysilicon strips instead of the conventional loop-like configuration. It is shown that these devices sense the millimeter wave radiation beyond the infrared. The polarity and frequency dependence of the sensitivity prove that these strips behave as absorbing antennas towards the microwave/millimeter ...

Wave-particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However...