Abstract
The random density fluctuations observed in the solar wind plasma crucially influence on the Langmuir wave turbulence generated by energetic electron beams ejected during solar bursts. Those are powerful phenomena consisting of a chain of successive processes leading ultimately to strong electromagnetic emissions. The small-scale processes governing the interactions between the waves, the beams and the inhomogeneous plasmas need to be studied to explain such macroscopic phenomena. Moreover, the complexity induced by the plasma irregularities requires to find new approaches and modelling. Therefore theoretical and numerical tools were built to describe the Langmuir wave turbulence and the beam’s dynamics in inhomogeneous plasmas, in the form of a self-consistent Hamiltonian model including a fluid description for the plasma and a kinetic approach for the beam. On this basis, numerical simulations were performed in order to shed light on the impact of the density fluctuations on the beam dynamics, the electromagnetic wave radiation, the generation of Langmuir wave turbulence, the waves’ coupling and decay phenomena involving Langmuir and low frequency waves, the acceleration of beam electrons, their diffusion mechanisms, the modulation of the Langmuir waveforms and the statistical properties of the radiated fields’ distributions. The paper presents the main results obtained in the form of a review.
Highlights
The solar corona and wind are turbulent and inhomogeneous plasmas involving random fluctuations of various levels and scales of their density, velocity and ambient magnetic field
Measurements [5] revealed that average levels of density fluctuations above 1% of the background plasma density exist in the solar wind with length scales around 100 km
After a section presenting the theoretical approach and the numerical modeling, different microprocesses involving wave-particle, wave-wave and wave-plasma interaction mechanisms at work in the development of Langmuir wave turbulence generated by beams in inhomogeneous solar wind plasmas are successively presented: electron beam dynamics, Langmuir wave turbulence, wave transformation effects on the inhomogeneities, wave coupling and resonant decay, beam acceleration and energy absorption, electron velocity diffusion through wave packets, comparison of Langmuir waveforms with space observations, electric wavefield statistical distributions
Summary
The solar corona and wind are turbulent and inhomogeneous plasmas involving random fluctuations of various levels and scales of their density, velocity and ambient magnetic field. They proposed a new approach to study microphysical phenomena occurring in the solar wind and coronal plasmas and built theoretical and numerical tools describing the dynamics of wave turbulence and beams in such inhomogeneous plasmas Those include the following key points: (i) preexisting realistic random fluctuations of the plasma density, velocity and ambient magnetic field, (ii) coupling effects between the slow and the fast waves’ dynamics,. After a section presenting the theoretical approach and the numerical modeling, different microprocesses involving wave-particle, wave-wave and wave-plasma interaction mechanisms at work in the development of Langmuir wave turbulence generated by beams in inhomogeneous solar wind plasmas are successively presented: electron beam dynamics, Langmuir wave turbulence, wave transformation effects on the inhomogeneities, wave coupling and resonant decay, beam acceleration and energy absorption, electron velocity diffusion through wave packets, comparison of Langmuir waveforms with space observations, electric wavefield statistical distributions. The last section states some conclusions and further perspectives
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