scholarly journals A generation mechanism for chorus emission

1999 ◽  
Vol 17 (1) ◽  
pp. 95-100 ◽  
Author(s):  
V. Y. Trakhtengerts
Keyword(s):  
Electron Distribution Function ◽  
Energetic Electron ◽  
Generation Mechanism ◽  
Phase Correlation ◽  
Particle Interactions ◽  
Backward Wave Oscillator ◽  
Cyclotron Instability ◽  
Wave Oscillator ◽  
Discrete Signals ◽  
Wave Particle Interactions

Abstract. A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO) regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.Key words. Magnetospheric physics (Energetic particles · trapped). Space plasma physics (wave-particle interactions; waves and instabilities)

Localized heating of the Martian topside ionosphere through the combined effects of magnetic pumping by large scale magnetosonic waves and pitch angle diffusion by whistler waves

2020 ◽  
Author(s):  
Christopher Fowler ◽  
Oleksiy Agapitov ◽  
Shaosui Xu ◽  
David Mitchell ◽  
Laila Andersson ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Large Scale ◽  
Local Heating ◽  
Electron Distribution Function ◽  
Topside Ionosphere ◽  
Particle Interactions ◽  
Whistler Waves ◽  
Compressive Wave ◽  
Superthermal Electron ◽  
Wave Particle Interactions

<p>We present Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of periodic (~ 25 s) large scale (100s km) magnetosonic waves propagating into the Martian dayside upper ionosphere. These waves adiabatically modulate the superthermal electron distribution function, and the induced electron temperature anisotropies drive the generation of observed electromagnetic whistler waves. The localized (in altitude) minimum in the ratio f<sub>pe</sub> / f<sub>ce</sub> provides conditions favorable for the local enhancement of efficient wave-particle interactions, so that the induced whistlers act back on the superthermal electron population to isotropize the plasma through pitch angle scattering. These wave-particle interactions break the adiabaticity of the large scale magnetosonic wave compressions, leading to local heating of the superthermal electrons during compressive wave `troughs'. Further evidence of this heating is observed as the subsequent phase shift between the observed perpendicular-to-parallel superthermal electron temperatures and compressive wave fronts. Such a heating mechanism may be important at other unmagnetized bodies such as Venus and comets.</p>

scholarly journals Significance of Wave-Particle Interaction Analyzer for direct measurements of nonlinear wave-particle interactions

2013 ◽  
Vol 31 (3) ◽  
pp. 503-512 ◽  
Author(s):  
Y. Katoh ◽  
M. Kitahara ◽  
H. Kojima ◽  
Y. Omura ◽  
S. Kasahara ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Velocity Vector ◽  
Statistical Significance ◽  
Particle Interaction ◽  
Energetic Electron ◽  
Particle Interactions ◽  
Whistler Mode ◽  
Wave Particle Interaction ◽  
Energetic Electrons ◽  
Wave Particle Interactions

Abstract. In the upcoming JAXA/ERG satellite mission, Wave Particle Interaction Analyzer (WPIA) will be installed as an onboard software function. We study the statistical significance of the WPIA for measurement of the energy transfer process between energetic electrons and whistler-mode chorus emissions in the Earth's inner magnetosphere. The WPIA measures a relative phase angle between the wave vector E and velocity vector v of each electron and computes their inner product W, where W is the time variation of the kinetic energy of energetic electrons interacting with plasma waves. We evaluate the feasibility by applying the WPIA analysis to the simulation results of whistler-mode chorus generation. We compute W using both a wave electric field vector observed at a fixed point in the simulation system and a velocity vector of each energetic electron passing through this point. By summing up Wi of an individual particle i to give Wint, we obtain significant values of Wint as expected from the evolution of chorus emissions in the simulation result. We can discuss the efficiency of the energy exchange through wave-particle interactions by selecting the range of the kinetic energy and pitch angle of the electrons used in the computation of Wint. The statistical significance of the obtained Wint is evaluated by calculating the standard deviation σW of Wint. In the results of the analysis, positive or negative Wint is obtained at the different regions of velocity phase space, while at the specific regions the obtained Wint values are significantly greater than σW, indicating efficient wave-particle interactions. The present study demonstrates the feasibility of using the WPIA, which will be on board the upcoming ERG satellite, for direct measurement of wave-particle interactions.

Energetic electron precipitation via oblique whistler mode chorus emissions in the outer radiation belt

2021 ◽  
Author(s):  
Yikai Hsieh ◽  
Yoshiharu Omura
Keyword(s):  
Cyclotron Resonance ◽  
Energetic Electron ◽  
Particle Simulation ◽  
Electron Precipitation ◽  
Particle Interactions ◽  
Outer Radiation Belt ◽  
Whistler Mode ◽  
Mode Wave ◽  
Whistler Mode Wave ◽  
Wave Particle Interactions

<p>Whistler mode chorus emissions in the Earth’s magnetosphere cause energetic electron precipitation and the associated pulsating aurora. First-order cyclotron resonance in parallel whistler mode wave-particle interactions is the main mechanism of the precipitation. Not only cyclotron resonance but also Landau resonance and higher-order cyclotron resonances occur in the oblique whistler mode wave-particle interactions. Especially, electrons can be accelerated and scattered to lower equatorial pitch angles rapidly via Landau resonance. We apply test particle simulation and the Green’s function method to check the energetic electron precipitation caused by oblique chorus emissions. We simulate the wave-particle interactions around L=4.5 for electron ranges from 10 keV to a few MeV. We further compare the precipitation fluxes between parallel and oblique chorus emissions. Our simulation result reveals that oblique chorus emissions lead to more electron precipitation than parallel chorus emissions. At kinetic energy E < 100 keV, the electron precipitation ratio (oblique case/parallel case) is about 1.3. At 100 keV < E < 0.5 MeV, the ratio is greater than 2. At E > 0.5 MeV, the ratio is greater than 2 orders. Multiple resonances effect in the oblique whistler mode wave-particle interactions is the reason for the greater precipitation.</p>

scholarly journals Spectral characteristics of waves and particles in the model of cyclotron wave-particle interactions near plasmapause

1999 ◽  
Vol 17 (3) ◽  
pp. 351-357 ◽  
Author(s):  
D. l. Pasmanik ◽  
V. Y. Trakhtengerts
Keyword(s):  
Spectral Characteristics ◽  
Wave Spectrum ◽  
Energetic Electron ◽  
Space Plasma ◽  
Quantitative Model ◽  
Energetic Particles ◽  
Particle Interactions ◽  
Space Plasma Physics ◽  
Evening Sector ◽  
Wave Particle Interactions

Abstract. Further analysis of energetic electron precipitation at the evening sector of magnetosphere is performed. In the framework of the quantitative model of cyclotron wave-particle interactions developed in the previous Pasmanik et al. paper, the case of finite spread over energies of initial energetic electron distribution is studied. The solution for distribution function of energetic electron is found. The energetic spectrum of trapped and precipitating electrons and whistler wave spectrum are analysed.Key words. Magnetospheric physics (energetic particles · precipitating; energetic particles · trapped); · Space plasma physics (wave-particle interactions).

scholarly journals Generation mechanism for VLF chorus emissions observed at a low-latitude ground station

2004 ◽  
Vol 22 (6) ◽  
pp. 2067-2072 ◽  
Author(s):  
A. K. Singh ◽  
K. Rönnmark
Keyword(s):  
Magnetic Activity ◽  
Generation Mechanism ◽  
Spectral Features ◽  
Generation Process ◽  
Low Latitude ◽  
Backward Wave Oscillator ◽  
Ground Station ◽  
Cyclotron Maser ◽  
Wave Oscillator ◽  
Good Agreement

Abstract. A detailed spectral analysis of VLF chorus emissions observed at the low-latitude ground station Gulmarg (geomag. lat., 24° 26' N, geomag. long., 147° 9' E, L=1.28) during the strong magnetic activity on 7-8 March 1986 have been carried out, which shows that each chorus element originates from the upper edge of the underlying hiss band. To explain various temporal and spectral features of these emissions, a possible generation mechanism has been presented based on the backward wave oscillator regime of the magnetospheric cyclotron maser. On the basis of this model, we have computed various chorus parameters as well as some magnetospheric parameters affecting the generation process. A comparison of the observed chorus characteristics with the proposed generation mechanism shows a good agreement.

scholarly journals A quantitative model for cyclotron wave-particle interactions at the plasmapause

1998 ◽  
Vol 16 (3) ◽  
pp. 322-330 ◽  
Author(s):  
D. L. Pasmanik ◽  
V. Y. Trakhtengerts ◽  
A. G. Demekhov ◽  
A. A. Lyubchich ◽  
E. E. Titova ◽  
...  
Keyword(s):  
Magnetic Storm ◽  
Energetic Electron ◽  
Quantitative Model ◽  
Electron Precipitation ◽  
Precipitation Pattern ◽  
Particle Interactions ◽  
Particle Injection ◽  
Whistler Mode Waves ◽  
Plasma Theory ◽  
Wave Particle Interactions

Abstract. The formation of a zone of energetic electron precipitation by the plasmapause, a region of enhanced plasma density, following energetic particle injection during a magnetic storm, is analyzed. Such a region can also be formed by detached cold plasma clouds appearing in the outer magnetosphere by restructuring of the plasmasphere during a magnetic storm. As a mechanism of precipitation, wave-particle interactions by the cyclotron instability between whistler-mode waves and electrons are considered. In the framework of the self-consistent equations of quasi-linear plasma theory, the distribution function of trapped electrons and the electron precipitation pattern are found. The theoretical results are compared with experimental data obtained from NOAA satellites.Key words. Magnetospheric physics · Energetic particles · Precipitating and trapped · Plasma waves and instabilities

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