Energy transfer from lower energy to higher-energy electrons mediated by whistler waves in the radiation belts. ELECTRON ENERGIZATION IN RADIATION BELTS.
We study the problem of energy exchange between waves and particles, which leads to energization of the latter, in an unstable plasma typical of the radiation belts. The ongoing Van Allen Probes space mission brought this problem among the most discussed in space physics. A free energy which is present in an unstable plasma provides the indispensable condition for energy transfer from lower energy particles to higher-energy particles via resonant wave-particle interaction. This process is studied in detail by the example of electron interactions with whistler mode wave packets originated from lightning-induced emission. We emphasize that in an unstable plasma, the energy source for electron energization is the energy of other particles, rather than the wave energy as is often assumed. The way by which the energy is transferred from lower energy to higher-energy particles includes two processes that operate concurrently, in the same space-time domain, or sequentially, in different space-time domains, in which a given wave packet is located. In the first process, one group of resonant particles gives the energy to the wave. The second process consists in wave absorption by another group of resonant particles, whose energy therefore increases. We argue that this mechanism represents an efficient means of electron energization in the radiation belts.
We study the interaction between energetic protons of the Earth’s radiation belts and quasi-electrostatic whistler mode waves. The nature of these waves is well known: whistler waves, which are excited in the magnetosphere due to cyclotron instability, enter the resonant regime of propagation and become quasielectrostatic, while their amplitude significantly increases. Far enough from the equator where proton gyrofrequency and transversal velocity increase the nonlinear interaction between these waves and energetic protons becomes possible. We show that plasma inhomogeneity may destroy cyclotron resonance between wave and proton on the time scale of the order of particle gyroperiod which in fact means the absence of cyclotron resonance; nevertheless, the interaction between waves and energetic particles remains nonlinear. In this case, particle dynamics in the phase space has the character of diffusion; however, the diffusion coefficients are determined by the averaged amplitude of the wave field, but not by its resonant harmonics. For real parameters of the waves and magnetospheric plasma, proton pitch-angle diffusion leading to their precipitation from the magnetosphere becomes essential.
Quantum dot (QD) solids represent a new type of condensed matter drawing high fundamental and applied interest. Quantum confinement in individual QDs, combined with macroscopic scale whole materials, leads to novel exciton and charge transfer features that are particularly relevant to optoelectronic applications. This Perspective discusses the structure of semiconductor QD solids, optical and spectral properties, charge carrier transport, and photovoltaic applications. The distance between adjacent nanoparticles and surface ligands influences greatly electrostatic interactions between QDs and, hence, charge and energy transfer. It is almost inevitable that QD solids exhibit energetic disorder that bears many similarities to disordered organic semiconductors, with charge and exciton transport described by the multiple trapping model. QD solids are synthesized at low cost from colloidal solutions by casting, spraying, and printing. A judicious selection of a layer sequence involving QDs with different size, composition, and ligands can be used to harvest sunlight over a wide spectral range, leading to inexpensive and efficient photovoltaic devices.
The possibility of long-term operation of the equipment on satellites is closely related to the dynamics of the electron fluxes of the Earth’s external radiation belt (SRW), an increase in radiation loads can lead to disruption of the operation of electronic systems: the appearance of surface currents and the appearance of spontaneous electric discharges. The structure of the electron flow of the SRWS is formed under the influence of a number of competing processes of transportation, acceleration and particle loss that occur inside the magnetosphere and at its boundaries under the influence of the solar wind (NE). Significant variations in the SREP electron flux associated with the restructuring of the structure of the SV fluxes cause significant changes in the structure of the energy spectra of the SRPS electrons, which leads to a change in radiation dose loads for spacecraft equipment. The paper analyzes the dynamics of the energy spectra of the SCL electrons for the period of the minimum solar activity of the 23rd solar cycle in 2007 and in 2009 and shows the effect of two different sources of SW on the formation of the flows of SCW electrons, high-speed and slow SW flows.
VLF (VeryLow Frequency) spectrograms registered at Kannuslehto ground station, after
cleaning them from strong sferics, reveal VLF noise suppression by whistlers and whistler echo trains,
which consists in significant reduction in the noise spectral power after a strong whistler event.We have
found similar effect in the VLF data from Van Allen Probe B taken in the equatorial region on L-shell ∼3.
Detailed analysis of the data shows that the whistler echo train and the VLF noise have small wave normal
angles. Based on this observation, we limit our analysis to parallel (ducted) whistler wave propagation. The
persistence of whistler echo train, as well as the VLF noise, suggests that in the events under discussion,
plasma is unstable in the frequency range corresponding to the observed VLF noise band. In an attempt to
explain the effect of VLF noise suppression, we follow up the long-standing idea that relates this effect to
the reduction of free energy in the unstable plasma distribution by whistler echo train. To develop this idea
into qualitative model, we have studied the motion of energetic electrons, responsible for the noise
generation, in the field of ducted whistler echo train.We show that energetic electrons that make the main
contribution to the growth rate of VLF noise, during their bounce oscillations in the magnetosphere, are
subject to multiple resonant impacts from the whistler echo train. These lead to energetic electron
diffusion in the phase space and the corresponding reduction in free energy of the unstable distribution.
Electron-positron medium is considered as a promising implementation of powerful microwave devices on multibeam electron and positron streams. Simulation of the resonant interaction processes in electron-positron substance is carried out using macroscopic wave functions of electrons and positrons of macroscopic quantum theory. It is shown that at optimum space charge observed nonlinear resonance exchange process leading to the compensation of the Coulomb field.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.