Multi-dimensional Vlasov simulations on trapping-induced sidebands of Langmuir waves

Type III radio bursts are radio emissions associated with solar flares. They are considered to be caused by electron beams travelling from the solar corona to the solar wind. Magnetic reconnection is a possible accelerator of electron beams in the course of solar flares since it causes unstable distribution functions and density inhomogeneities (cavities). The properties of radio emission by electron beams in an inhomogeneous environment are still poorly understood. We capture the nonlinear kinetic plasma processes of the generation of beam-related radio emissions in inhomogeneous plasmas by utilizing fully kinetic particle-in-cell code numerical simulations. Our model takes into account initial electron velocity distribution functions (EVDFs) as they are supposed to be created by magnetic reconnection. We focus our analysis on low-density regions with strong magnetic fields. The assumed EVDFs allow two distinct mechanisms of radio wave emissions: plasma emission due to wave–wave interactions and so-called electron cyclotron maser emission (ECME) due to direct wave–particle interactions. We investigate the effects of density inhomogeneities on the conversion of free energy from the electron beams into the energy of electrostatic and electromagnetic waves via plasma emission and ECME, as well as the frequency shift of electron resonances caused by perpendicular gradients in the beam EVDFs. Our most important finding is that the number of harmonics of Langmuir waves increases due to the presence of density inhomogeneities. The additional harmonics of Langmuir waves are generated by a coalescence of beam-generated Langmuir waves and their harmonics.

Download Full-text

Vlasov simulation of amplitude-modulated Langmuir waves

Physics of Plasmas ◽

10.1063/1.2348088 ◽

2006 ◽

Vol 13 (9) ◽

pp. 092304 ◽

Cited By ~ 12

Author(s):

Takayuki Umeda

Keyword(s):

Langmuir Waves

Download Full-text

New Exact Solutions of the System of Equations for the Ion Sound and Langmuir Waves by ETEM

Mathematical and Computational Applications ◽

10.3390/mca21020011 ◽

2016 ◽

Vol 21 (2) ◽

pp. 11 ◽

Cited By ~ 3

Author(s):

Seyma Tuluce Demiray ◽

Hasan Bulut

Keyword(s):

Exact Solutions ◽

System Of Equations ◽

Langmuir Waves ◽

New Exact Solutions

Download Full-text

Parametric instabifity of transverse and Langmuir waves in a plasma

Journal of Plasma Physics ◽

10.1017/s0022377800026076 ◽

1975 ◽

Vol 13 (2) ◽

pp. 317-326 ◽

Cited By ~ 2

Author(s):

Kai Fong Lee

Keyword(s):

Growth Rate ◽

Electromagnetic Field ◽

Kinetic Model ◽

Multiple Time ◽

Multiple Time Scale ◽

Threshold Intensity ◽

Langmuir Waves ◽

Scale Perturbation ◽

The Subject ◽

Parametric Instabilities

The parametric excitation of transverse and Langmuir waves by an externally-driven electromagnetic field of frequency (ω0 > 2ωp) in a warm and collisional plasma is studied, using the fluid equations. By an application of the multiple- time-scale perturbation method, the threshold intensity and the growth rate above threshold are obtained. The results are compared with those of Goldman (1969) and Prasad (1968), both of whom worked with a kinetic model.The theory of parametric instabilities in plasmas has been the subject of numerous investigations in recent years. Broadly speaking, the instabilities can be grouped into two categories: those for which the excited waves are purely electrostatic (see e.g. DuBois & Goldman 1965, 1967; Silin 1965; Lee & Su 1966; Jackson 1967; Nishikawa 1968; Kaw & Dawson 1969; Tzoar 1969; Sanmartin 1970; McBride 1970; Perkins & Flick 1971; Fejer & Leer 1972a, b; Bezzerides & Weinstock 1972; DuBois & Goldman 1972), and those for which one of the excited waves is electromagnetic (see e.g. Goldman & Dubois 1965; Montgomery & Alexeff 1966; Chen & Lewak 1970; Bodner & Eddleman 1972; Fejer & Leer 1972b; Lee & Kaw 1972; Forslund et al. 1972).

Download Full-text

Temporal evolution of reactive and resistive nonlinear instabilities

Journal of Plasma Physics ◽

10.1017/s0022377800012745 ◽

1987 ◽

Vol 38 (3) ◽

pp. 473-481 ◽

Cited By ~ 3

Author(s):

D. B. Melrose

Keyword(s):

Electron Number Density ◽

Temporal Evolution ◽

Random Phase ◽

Low Frequency ◽

Rate Of Change ◽

Number Density ◽

Wave Instability ◽

Langmuir Waves ◽

Secular Evolution ◽

Coherent Wave

A kinetic theory for nonlinear processes involving Langmuir waves, developed in an earlier paper, is extended through consideration of three aspects of the temporal evolution, (i) Following Falk & Tsytovich (1975). the dynamic equation for the rate of change of one amplitude at t is expressed as an integral over T of the product of two amplitudes at t – T and a kernel functionf(T); two generalizations of Falk & Tsytovich's form (f(T) ∝ T) that satisfy the requirement f(∞) = 0 are identified, (ii) It is shown that the low-frequency or beat disturbance may be described in terms of fluctuations in the electron number density, and that its time evolution involves an operator that is essentially the inverse of f(t). (iii) The transition from oscillatory evolution in the reactive or ‘coherent-wave’ version of the three-wave instability to the secular evolution of the resistive or ‘random-phase’ version is discussed qualitatively.

Download Full-text