Interaction Of Energetic Electrons Research Articles

Resonant Interaction of Energetic Electrons with Radio Emission in the Magnetospheres of Exoplanets

Resonant Interaction of Energetic Electrons with Radio Emission in the Magnetospheres of Exoplanets

Scattering of energetic electrons through nonlinear cyclotron resonance with coherent whistler-mode hiss emissions

Recent observations have revealed that plasmaspheric hiss consists of many discrete waves called “hiss elements.” However, the interaction of energetic electrons (10 keV to several MeV) with the plasmaspheric hiss has only been simulated by the quasilinear (QL) diffusion theory, which does not take the fine wave structure into account. The QL theory cannot address nonlinear particle motions determined by the inhomogeneity factor, which influences the scattering of electrons in pitch angle and energy. This study aims to identify differences between the nonlinear wave–particle interaction and QL theory for plasmaspheric hiss emissions. We conduct test particle simulations to demonstrate the nonlinear interactions between hiss waves and electrons. The nonlinear theory is used to model hiss elements consisting of discrete frequencies and continuous phases. Unlike the other theories, the frequency and amplitude variations in time of the hiss packet are taken into account. Frequencies of the packets are determined to satisfy the separability criterion; when the criterion is met, resonance overlapping is absent, and the electrons can generate each wave element independently. The realistic simulation model of hiss waves reproduces the scattering of electrons by both first- and second-order resonances. We also evaluate the efficiency of electron scattering by calculating nonlinear diffusion coefficients. The diffusion coefficient of equatorial pitch angle is of the same order of magnitude as those calculated by the QL diffusion theory, while we find the effective acceleration of resonant electrons by successive nonlinear trapping, which is not evaluated by the QL theory.

Resonant Interaction of Energetic Electrons With Radio Emission in the Magnetospheres of Exoplanets

Resonant Interaction of Energetic Electrons With Radio Emission in the Magnetospheres of Exoplanets

The Role of the Anomalous Doppler Effect in the Interaction of Energetic Electrons with Whistler Turbulence in Flare Loops

The Role of the Anomalous Doppler Effect in the Interaction of Energetic Electrons with Whistler Turbulence in Flare Loops

Novel single-step synthesis and shape transformation of Au/CuO micro/nanocomposites using plasma-liquid interaction

We report a novel single-step synthesis method of metal/metal oxide composites and transformation of the shape of the oxide material by Plasma-Liquid Interaction. Considering the potential applications of noble metal nanoparticle decorated copper oxide composites, we synthesize Au/CuO micro/nanocomposites by generating plasma between two copper electrodes inside a gold precursor (HAuCl4) solution. Simultaneous synthesis of CuO and Au nanoparticles from the electrode material and from the precursor solution respectively is possible due to the interaction of energetic electrons and other active species formed in the plasma zone. Moreover, the process does not require any external stabilizing and reducing chemical agents. The method provides a remarkable tunability of the materials’ physical and chemical properties by only controlling the precursor solution concentration. By controlling process parameters, the shape of CuO particles can be transformed from spindles to sheet-like and the size of Au nanoparticles can also be varied. It influences the particles’ specific surface area and total pore volume. Plasmonic property of Au nanoparticles is also observed i.e. optical tunability can be achieved. The process is found to be effective for synthesis of desired nanomaterials having various energy storage and solar light-driven photocatalytic applications.

Regimes of Resonant Interactions of Electrons with Auroral Kilometric Radiation

We analyze the resonant interaction of energetic electrons with auroral kilometric radiation (AKR). Possible regimes of such an interaction are studied on the basis of a numerical solution of the particle motion equations in a given field of a quasi-monochromatic AKR wave packet. It is shown that for realistic wave amplitudes 0.2–0.4 V/m, the interaction can be highly nonlinear. As a result of nonlinear interaction, both a substantial (approximately twofold) acceleration of particles and a decrease in their energy (by about 20–50%) are possible. With realistic plasma and wave packet parameters, electrons with initial energies of the order of 10 keV are accelerated, and for electrons with initial energies of several tens of keV, the interaction leads to a decrease in energy.

Precipitation of Energetic Electrons from the Earth’s Radiation Belt Stimulated by High-Power HF Radio Waves for Modification of the Midlatitude Ionosphere

Based on the results of the experiments performed in 2005–2010 within the framework of the Sura—DEMETER program, we analyze the features of the precipitations of energetic electrons (with energies E ≈ 100 keV) from the Earth’s radiation belt. The modification of the ionospheric F2 region was conducted by means of high-power HF O-mode radio waves radiated in the CW regime. The precipitations were detected using the equipment onboard DEMETER, a French microsatellite. The conditions of precipitation appearance were determined, and it was found that the electron precipitation region was stretched along the geomagnetic meridian to a distance of 1300 km; the size of the region in the transverse direction is about 400 km. It was shown by ionosonde measurements that such precipitations lead to increased absorption of radio waves in the lower ionosphere. It is assumed that the mechanism for precipitation of electrons from the Earth’s radiation belt is determined by the interaction of energetic electrons with VLF radio waves, which are generated due to the interaction of the amplitude-unmodulated O-mode pump wave with the ionospheric plasma near the wave reflection height.

Synthesis of the Smallest Member of the Silylketene Family: H3 SiC(H)=C=O.

Exploiting photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS) combined with electronic structure calculations, it is shown that the hitherto elusive silylketene molecule (H3 SiC(H)=C=O)-the isovalent counterpart of the well-known methylketene molecule-is forming via interaction of energetic electrons with low-temperature silane-carbon monoxide ices. In combination with the infrared spectroscopically detected triplet dicarbon monoxide reactant, electronic structure calculations suggest that dicarbon monoxide reacts with silane via a de facto insertion of the terminal carbon atom into a silicon-hydrogen single bond. This is followed by non-adiabatic reaction dynamics triggered by the heavy silicon atom intersystem crossing from the triplet to the singlet manifold, eventually leading to the formation of silylketene. The non-equilibrium nature of the elementary reactions within the exposed ices results in an exciting and novel chemistry which cannot be explored via traditional preparative chemistry. Since the replacement of hydrogen in silane can introduce side groups such as silyl or alkyl, the reaction of triplet dicarbon monoxide with silane represents the parent system for a previously disregarded reaction class revealing an elegant path to access the largely reactive group of silylketenes.

PARTICLE SCATTERING OFF OF RIGHT-HANDED DISPERSIVE WAVES

ABSTRACT Resonant scattering of fast particles off low frequency plasma waves is a major process determining transport characteristics of energetic particles in the heliosphere and contributing to their acceleration. Usually, only Alfvén waves are considered for this process, although dispersive waves are also present throughout the heliosphere. We investigate resonant interaction of energetic electrons with dispersive, right-handed waves. For the interaction of particles and a single wave a variable transformation into the rest frame of the wave can be performed. Here, well-established analytic models derived in the framework of magnetostatic quasi-linear theory can be used as a reference to validate simulation results. However, this approach fails as soon as several dispersive waves are involved. Based on analytic solutions modeling the scattering amplitude in the magnetostatic limit, we present an approach to modify these equations for use in the plasma frame. Thereby we aim at a description of particle scattering in the presence of several waves. A particle-in-cell code is employed to study wave–particle scattering on a micro-physically correct level and to test the modified model equations. We investigate the interactions of electrons at different energies (from 1 keV to 1 MeV) and right-handed waves with various amplitudes. Differences between model and simulation arise in the case of high amplitudes or several waves. Analyzing the trajectories of single particles we find no microscopic diffusion in the case of a single plasma wave, although a broadening of the particle distribution can be observed.

Interaction of energetic electrons with dust whistler-mode waves in magnetospheric dusty plasmas

In this Letter, a new conceptual approach has been presented to investigate the interaction of energetic electrons with dust whistler-mode waves in magnetospheric dusty (complex) plasmas. Dust whistler-mode waves generated in the presence of charged dust grains in the magnetized dusty plasma, can scatter the launched electrons into the loss-cone leading to precipitation into the upper atmosphere which is an important loss process in the radiation belts and provides a major source of energy for the diffuse and pulsating aurora. To study the scattered electrons and chaotic regions, a Hamiltonian model of the electron-dust wave interaction has been employed in the magnetospheric plasma by considering the launched electron beam self-fields. Numerical simulations indicate that an electron beam interacting with the whistler-mode wave can easily trigger chaos in the dust-free plasma, while in the presence of dust charged grains in the plasma, the chaotic regions are quenched to some extent in the magnetosphere. Consequently, the rate of scattered electrons into the loss-cone reduces for the regions that the dust grains are present.

Thermal and non-thermal emission from reconnecting twisted coronal loops

Twisted magnetic fields should be ubiquitous in flare-producing active regions where the magnetic fields are strongly non-potential. It has been shown that reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops. This scenario can be an alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. We use a combination of MHD simulations and test-particle methods, which describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD, and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us estimate thermal X-ray emission intensities. The electric and magnetic fields obtained are used to calculate electron trajectories using the guiding-centre approximation. These trajectories combined with the MHD plasma density distributions let us deduce synthetic HXR bremsstrahlung intensities. Our simulations emphasise that the geometry of the emission patterns produced by hot plasma in flaring twisted coronal loops can differ from the actual geometry of the underlying magnetic fields. The twist angles revealed by the emission threads (SXR) are consistently lower than the field-line twist present at the onset of the kink-instability. HXR emission due to the interaction of energetic electrons with the stratified background are concentrated at the loop foot-points in these simulations, even though the electrons are accelerated everywhere within the coronal volume of the loop. The maximum of HXR emission consistently precedes that of SXR emission, with the HXR light-curve being approximately proportional to the temporal derivative of the SXR light-curve.

On the interaction of energetic electrons with a tearing mode in density-sweeping tokamak plasmas

We present a detailed study on the interaction between energetic electrons and the m/n = 2/1 tearing mode (m, n are respectively the poloidal and toroidal mode number) which was investigated in a deliberate experiment via actively controlling the bulk electron density (Li et al 2014 Nucl. Fusion 54 042001). Energetic electrons were generated by the residual loop voltage in the ohmically heated plasma where periodic bursts of magnetic perturbations were frequently observed. The frequency evolution of the mode is similar to the well-known fishbone (m/n = 1/1) or the ‘off-axis’ fishbone in high-beta plasma (Heidbrink et al 2011 Plasma Phys. Control. Fusion 53 085028), but demonstrates the characteristic of a tearing mode. In particular, it can increase the average intensity of H-alpha radiation as the mode grows, which is distinctive from the following oscillatory phase. The dynamics of the mode are strongly influenced by the increasing background electron density, suggesting a collisionality dependence. This qualitatively agrees with the prediction of a drift kinetic theory.

Getting Started with NIST DTSA-II

Since its introduction in 2007, DTSA-II has been adopted by numerous researchers, and it has been integrated into numerous educational programs. This is the first of a series of articles in Microscopy Today that will appear in the upcoming months to provide an introduction to use of the product. These articles also will provide details of how DTSA-II can be used to implement best practices for microanalysis in your laboratory or in your teaching environment. These articles will demonstrate how to form the most accurate type of spectrum quantification—standards-base quantification—as well as how to use simulation to optimize various types of measurement problems. They will focus on using DTSA-II to understand the physical process including the interaction of energetic electrons with your sample and the propagation of x-rays through matter and to the detector.

FORMATION OF MOLECULAR HYDROGEN FROM METHANE ICE

To study the formation of molecular hydrogen in the wake of the processing of interstellar ices by energetic cosmic-ray particles, we investigated the interaction of energetic electrons, as formed in the track of galactic cosmic-ray particles, with deuterated methane ices (CD4) at 11 K. The energetic electrons mimic energy-transfer processes that occur in the track of the trajectories of energetic cosmic-ray particles; deuterated methane ice was utilized to discriminate the molecular deuterium (m/z = 4) formed during the radiation exposure from the residual molecular hydrogen gas (m/z = 2) released inside the ultrahigh vacuum scattering chamber from outgassing of the stainless steel material. The ices were characterized online and in situ using Fourier transform infrared spectroscopy, while the evolution of the molecular deuterium (D2) into the gas phase was monitored using a mass spectrometer. A mass spectrometric signal proportional to the number density of the deuterium molecules generated inside the ice and released during the irradiation was analyzed kinetically using a set of coupled rate equations. From the fit to the experimental data, we obtain activation energies for the diffusion of atomic deuterium (E 0 = 37 ± 1 meV), and for the desorption of atomic (E 1 = 32 ± 1 meV) and molecular deuterium (E 2 = 32 ± 1 meV). These energies are placed in context and then transferred to atomic and molecular hydrogen to yield astrophysically relevant data. The experimental yield of molecular deuterium is then used to calculate the formation rate of molecular hydrogen due to cosmic-ray interaction with ice-covered grains in dense clouds.

Transit time scattering of energetic electrons due to equatorially confined magnetosonic waves

Recent analysis using quasilinear theory (QLT) has shown that magnetosonic (MS) waves are able to accelerate electrons to relativistic energies on fast time scales (∼1 day). However, the large obliquity of the wave and typical equatorial confinement of the MS wave power create conditions that bring into question the fundamental applicability of QLT to this problem. In this paper, a test particle code is used to model the interaction of energetic electrons with fast MS waves, to test the results of QLT analysis, and to investigate any potential nonlinear effects. It is found that in the expected Landau‐resonant region, test particle results show good agreement with QLT, but outside this region, the spatial confinement of the low‐frequency waves introduces a new source of scattering which we call “transit time diffusion.” Although this mechanism is weaker than resonant scattering, it is nevertheless able to interfere with the Landau resonance to create nulls in the energy‐pitch angle diffusion map, and the scattering persists even when resonant diffusion is completely removed.

Measurement of the bremsstrahlung spectra generated from thick targets with Z=2–78 under the impact of 10 keV electrons

We present new experimental data on thick target bremsstrahlung spectra generated from the interaction of energetic electrons with bulk matter. The ‘photon yields’ in terms of double differential cross-sections (DDCS) are measured for pure elements of thick targets: Ti (Z = 22), Ag (Z = 47), W (Z = 74) and Pt (Z = 78) under the impact of 10 keV electrons. Comparison of DDCS obtained from the experimental data is made with those predicted by Monte-Carlo (MC) calculations using PENELOPE code. A close agreement between the experimental data and the MC calculations is found for all the four targets within the experimental error of 16%. Furthermore, the ratios of DDCS of bremsstrahlung photons emitted from Ag, W and Pt with those from Ti as a function of photon energy are examined with a relatively lower uncertainty of about 10% and they are compared with MC calculations. A satisfactory agreement is found between the experiment and the calculations within some normalizing factors. The variations of DDCS as a function of Z and of photon energy are also studied which show that the DDCS vary closely with Z; however, some deviations are observed for ‘tip’ photons emitted from high Z targets.

Nonlinear interaction of energetic electrons with large amplitude chorus

The effect of large amplitude chorus on energetic, radiation‐belt electrons is evaluated using a general, relativistic, oblique, test‐particle code. Three specific cases are examined: (A) Low‐amplitude waves interacting at low‐latitudes exhibit the expected, linear scattering which leads to large‐scale diffusive behavior. (B) Large‐amplitude waves interacting at low‐latitudes result in monotonic decreases in pitch‐angle and energy due to a resonance dislocation effect, leading to large‐scale de‐energization and particle loss. (C) Large‐amplitude waves interacting obliquely at high latitudes result in a combination of the above behaviors, as well as nonlinear phase‐trapping which leads to rapid, dramatic increases in both energy and pitch‐angle of a small portion of the test‐particles. These results suggest that the intensity of individual, discrete wave elements is critical for quantifying the large‐scale dynamics of the radiation‐belts.

Radiation by energetic electrons accelerated by wave-particle interaction: a plausible mechanism for x-ray emission from the Venus mantle

Abstract. In this paper it is argued that recently observed x-ray emission from non-magnetic planets (Dennerl et al., 2002) can be explained as a combination of bremsstrahlung and line K-shell radiation produced by the interaction of energetic electrons with the neutral atmosphere. Numerical simulations show that the modified two stream instability can generate energetic 100 eV electrons that are observed and these electrons can produce x-ray emission.

Hiss-triggered chorus emissions at Indian stations

Some examples of chorus emissions emanating from the upper edge of the underlying hiss events recorded at the Indian Antarctic Station Maitri (geomag. lat.=62°S, long. 57.2° E, L=4.5) and low-latitude station Gulmarg (geomag. lat.=24°26′N, long. 147°09′E) are reported, in which intensity seems to decrease with increase in frequency and also it varies from event to event. It is proposed that resonance interaction of energetic electrons with wavelets present in the upper edge of hiss elements propagating in whistler mode under suitable condition behaves as a backward wave oscillator and generates chorus emissions. The minimum and the maximum value of interaction length, beam modulation period and temporal evolution of emitted wave frequency have been evaluated. Modulation period has been used to explain the periodicity in the recorded events and the temporal evolution of wave frequency has been used to explain the shape of dynamic spectrum of hiss-triggered emissions.

Runaway effects at the plasma boundary in ISTTOK

Experimental results on minor and major disruption events in discharges with runaway electrons in the small tokamak ISTTOK and corresponding numerical analysis are presented. Using the experimental data from the soft X-ray diagnostic the image of the plasma column in the presence of runaway electron instability and disruptions was reconstructed. The most probable zones of the interaction of energetic electrons with the plasma surrounding surfaces were detected as spots of the soft X-ray emission on the top and bottom parts of the plasma column during the development of the disruptions. Numerical analysis of the runaway instability allowed determining the runaway electrons characteristics, such as energy ( W eRA⩽30 keV) and density ( n RA∼(0.001–0.01) n e). On the basis of this analysis the level of electrostatic turbulence due to the instability was estimated.