Electron cyclotron resonance near the axis of the gas-dynamic trap

Propagation of an extraordinary electromagnetic wave in the vicinity of electron cyclotron resonance surface in an open linear trap is studied analytically, taking into account inhomogeneity of the magnetic field in paraxial approximation. Ray trajectories are derived from a reduced dispersion equation that makes it possible to avoid the difficulty associated with a transition from large propagation angles to the case of strictly longitudinal propagation. Our approach is based on the theory, originally developed by the Zvonkov and Timofeev [1], who used the paraxial approximation for the magnetic field strength, but did not consider the slope of the magnetic field lines, which led to considerable error, as has been recently noted by Gospodchikov and Smolyakova [2]. We have found ray trajectories in analytic form and demonstrated that the inhomogeneity of both the magnetic field strength and the field direction can qualitatively change the picture of wave propagation and significantly affect the efficiency of electron cyclotron heating of a plasma in a linear magnetic trap. Analysis of the ray trajectories has revealed a criterion for the resonance point on the axis of the trap to be an attractor for the ray trajectories. It is also shown that a family of ray trajectories can still reach the resonance point on the axis if the latter generally repels the ray trajectories. As an example, results of general theory are applied to the electron cyclotron resonance heating experiment which is under preparation on the Gas Dynamic Trap in the Budker Institute of Nuclear Physics [3]

Modeling of the M2 surface and internal tides and their seasonal variability in the Arctic Ocean: Dynamics, energetics and tidally induced diapycnal diffusion

Modeling results for the M2 surface and internal tides in the Arctic Ocean (AO) are presented. These incorporate the data on tidal dynamics and energetics and tidally induced diapycnal diffusion. A modified version of the 3D finite-element hydrostatic model QUODDY-4 is used as a basis for modeling. It is shown that the predicted surface tide differs slightly from that obtained from other tidal models, whereas the internal tidal waves (ITW) are less than those in oceans of moderate and low latitudes. It also appears that ITW themselves belong to the family of trapped waves. This finding, together with the modeling results for averaged (over a tidal cycle) horizontal transport per unit length of barotropic tidal energy and depth-integrated density of baroclinic tidal energy, suggests that the ITW generation site is placed to the northwest of the New Siberian Islands. A local rate of baroclinic tidal energy dissipation is found to increase away from the bottom as observed on Mid-Atlantic and Hawaiian ridges, but only within the bottom boundary layer, and two-three orders of magnitude less than in other oceans. Also, the ITW decay scale in both summer and winter lies over the range of its values (100–1000 km) for Mid-Atlantic and Hawaiian ridges. A tidal cycle-, depth- and area-averaged coefficient of diapycnal diffusion is greater than the kinematic viscosity and less (but not much) than the canonical value of the vertical eddy diffusivity in the deep ocean, prescribed in models of global ocean circulation. From this results the conclusion that tidally induced diapycnal diffusion can be meaningful in the formation of the AO climate

Adiabatic nonlinear waves with trapped particles: II. Wave dispersion

A general nonlinear dispersion relation is derived in a nondifferential form for an adiabatic sinusoidal Langmuir wave in collisionless plasma, allowing for an arbitrary distribution of trapped electrons. The linear dielectric function is generalized, and the nonlinear kinetic frequency shift $\omega_{\rm NL}$ is found analytically as a function of the wave amplitude $a$. Smooth distributions yield $\omega_{\rm NL} \propto \sqrt{a}$, as usual. However, beam-like distributions of trapped electrons result in different power laws, or even a logarithmic nonlinearity, which are derived as asymptotic limits of the same dispersion relation. Such beams are formed whenever the phase velocity changes, because the trapped distribution is in autoresonance and thus evolves differently from the passing distribution. Hence, even adiabatic $\omega_{\rm NL}(a)$ is generally nonlocal.Comment: submitted together with Papers I and II

Recombination limited energy relaxation in a BCS superconductor

We study quasiparticle energy relaxation at sub-kelvin temperatures by injecting hot electrons into an aluminium island and measuring the energy flux from electrons into phonons both in the superconducting and in the normal state. The data show strong reduction of the flux at low temperatures in the superconducting state, in qualitative agreement with the presented quasiclassical theory for clean superconductors. Quantitatively, the energy flux exceeds that from the theory both in the superconducting and in the normal state, possibly suggesting an enhanced or additional relaxation process

Magnetophonon resonance in photoluminescence excitation spectra of magnetoexcitons in GaAs/Al0.3Ga0.7As superlattice

Strong increase in the intensity of the peaks of excited magneto-exciton (ME) states in the photoluminescence excitation (PLE) spectra recorded for the ground heavy-hole magneto-excitons (of the 1sHH type) has been found in a GaAs/AlGaAs superlattice in strong magnetic field B applied normal to the sample layers. While varying B the intensities of the PLE peaks have been measured as functions of energy separation $\Delta E$ between excited ME peaks and the ground state of the system. The resonance profiles have been found to have maxima at $\Delta E_{\rm max}$ close to the energy of the GaAs LO-phonon. However, the value of $\Delta E_{\rm max}$ depends on quantum numbers of the excited ME state. The revealed very low quantum efficiency of the investigated sample allows us to ascribe the observed resonance to the enhancement of the non-radiative magneto-exciton relaxation rate arising due to LO-phonon emission. The presented theoretical model, being in a good agreement with experimental observations, provides a method to extract 1sHH magneto-exciton ``in-plane" dispersion from the dependence of $\Delta E_{\rm max}$ on the excited ME state quantum numbers.Comment: 9 pages, 6 figure