Demekhov A.G.,Institute of Applied Physics
Space Science Reviews | Year: 2012
We discuss the electromagnetic processes in the ULF range which are important for the coupling between the atmosphere, ionosphere, and magnetosphere (AIM). The main attention is given to the Pc1-2 frequency ranges (f≈0.1-10 Hz) where some natural resonances in the AIM system are located. In particular, we consider the resonant structures in the spectra of the magnetic background noise related to the Alfvén resonances in the ionosphere as a possible diagnostic tool for studies of the ionospheric parameters. We also discuss the self-excitation of Alfvén waves in the ionosphere due to the AIM coupling and the role of such waves in the acceleration of electrons in the upper ionosphere and magnetosphere. Precipitation of magnetospheric ions due to their interaction with the ion-cyclotron waves is analyzed in relation to the ionospheric current systems, formation of partial ring current, and the influence of the ionosphere-magnetosphere feedback on the generation of such waves. © 2011 Springer Science+Business Media B.V.
Subochev P.,Institute of Applied Physics
Optics Letters | Year: 2016
The idea of a method of cost-effective upgrades from an acoustic resolution photoacoustic microscope to a triplemodality imaging system is validated using phantoms. The newly developed experimental setup is based on a diode pumped solid state laser coupled to a fiber bundle with a spherically focused polyvinylidene fluoride detector integrated into the center of a ring shaped optical illuminator. Each laser pulse illuminating the sample performs two functions. While the photons absorbed by the sample provide a measurable optoacoustic (OA) signal, the photons absorbed by the detector provide the measurable diffuse reflectometry (DR) signal from the sample and the probing ultrasonic (US) pulse. At a 3 mm imaging depth, the axial resolution of the OA/US modalities is 38 μm/26 μm, while the lateral resolution of the DR/OA/US modalities is 3.5 mm/50 μm/35 μm. The maximum acquisition rate of the trimodal DR/OA/US A-scans is 2 kHz. © 2016 Optical Society of America.
Malykin G.B.,Institute of Applied Physics
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2010
It is shown that the Ritz ballistic hypothesis, which is based on the vector summation of the speed of light with the velocity of the radiation source, contradicts the fact of existence of the Sagnac effect. Based on a particular example of a three-mirror ring interferometer, it is shown that the application of the Ritz ballistic hypothesis leads to an obvious calculation error, namely, to the appearance of a difference in the propagation times of counterpropagating waves in the absence of rotation. A review is given of experiments and of results of processing of astronomical observations and discussions devoted to testing the Ritz ballistic hypothesis. A number of other physical phenomena that refute the Ritz ballistic hypothesis are considered. © Pleiades Publishing, Ltd., 2010.
Mirovitskii V.Y.,Institute of Applied Physics
Journal of the Optical Society of America B: Optical Physics | Year: 2014
Theory of second-harmonic generation (SHG) in reflection from the (0001) face of hexagonal centrosymmetric (6/mmm) crystals is developed in a phenomenological approach. The bulk (electric-quadrupole) contribution to azimuthal dependences of SHG response is completely isotropic, whereas the surface (electric-dipole) contribution consists of isotropic and anisotropic parts for the 3m surface symmetry. Anisotropy entirely depends on only one component of the surface nonlinear susceptibility. This allows one to extract it directly by simultaneous measurement of the amplitude and phase of the SH wave in the (s,S) or (p; S) experimental setup. The feature is very important, if the observed anisotropy is strong and makes the surface SHG probing for these crystals completely different from the cases of cubic, rhombohedral, and tetragonal centrosymmetric crystals. In the case of weak anisotropy, the estimation of other surface components from azimuthal or polarization measurements is analyzed in detail. © 2014 Optical Society of America.
Kharchenko V.,University of Augsburg |
Goychuk I.,Institute of Applied Physics
New Journal of Physics | Year: 2012
We study subdiffusive ratchet transport in periodically and randomly flashing potentials. A central Brownian particle is elastically coupled to the surrounding auxiliary Brownian quasi-particles, which account for the influence of the viscoelastic environment. Similar to standard dynamical modeling of Brownian motion, the external force influences only the motion of the central particle, not affecting directly the environmental degrees of freedom. Just a handful of auxiliary Brownian particles suffices to model subdiffusion over many temporal decades. Time modulation of the potential violates the symmetry of thermal detailed balance and induces an anomalous subdiffusive current which exhibits a remarkably small dispersion at low temperatures, as well as a number of other surprising features such as saturation at low temperatures, and multiple inversions of the transport direction upon a change of the driving frequency in the non-adiabatic regime. It is shown that the subdiffusive current is finite at zero temperature for random flashing and can be finite for periodic flashing for a certain frequency window. Our study generalizes classical Brownian motors towards operating in sticky viscoelastic environments such as the cytosol of biological cells or dense polymer solutions.© IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.