Wave-particle interactions in non-uniform plasma and the interpretation of Hard X-ray spectra in solar flares

Abstract

Context. High energy electrons accelerated during solar flare are abundant in the solar corona and in the interplanetary space. Commonly, the number and the energy of non-thermal electrons at the Sun is estimated using hard X-ray (HXR) spectral observations (e.g. RHESSI) and a single-particle collisional approximation. Aims. To investigate the role of the spectrally evolving Langmuir turbulence on the population of energetic electrons in the solar corona. Methods. We numerically simulate the relaxation of a power-law non-thermal electron population in a collisional inhomogeneous plasma including wave-particle, and wave-wave interactions. Results. The numerical simulations show that the long-time evolution of electron population above 20 keV deviates substantially from the collisional approximation when wave-particle interactions in non-uniform plasma are taken into account. The evolution of Langmuir wave spectrum towards smaller wavenumbers, due to large-scale density fluctuations and wave-wave interactions, leads to an effective acceleration of electrons. Furthermore, the time-integrated spectrum of non-thermal electrons, which is normally observed with HXR above 20 keV, is noticeably increased due to acceleration of non-thermal electrons by Langmuir waves. Conclusions. The results show that the observed HXR spectrum, when interpreted in terms of collisional relaxation, can lead to an overestimated number and energy of energetic electrons accelerated in the corona.

8 pages, 6 figures, submitted to Astronomy and Astrophysics Journal

References in corpus (8)

• Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares
• Deducing Electron Properties From Hard X-Ray Observations
• Nonlinear development of electron-beam-driven weak turbulence in an inhomogeneous plasma
• Dynamics of electron beams in the solar corona plasma with density fluctuations
• Dynamics of electron beams in the inhomogeneous solar corona plasma
• An alternative to the plasma emission model: Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts
• Numerical consideration of quasilinear electron cloud dynamics in plasma
• Vlasov-Maxwell, self-consistent electromagnetic wave emission simulations in the solar corona

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• Density fluctuations and the acceleration of electrons by beam-generated Langmuir waves in the solar corona
• A Classification Scheme For Turbulent Acceleration Processes In Solar Flares
• Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra
• Three dimensional particle-in-cell simulation of particle acceleration by circularly polarised inertial Alfven waves in a transversely inhomogeneous plasma
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• Resonance broadening due to particle scattering and mode-coupling in the quasi-linear relaxation of electron beams
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• Bridging High-Density, Electron Beam Coronal Transport and Deep Chromospheric Heating in Stellar Flares
• Solar plasma radio emission in the presence of imbalanced turbulence of kinetic-scale Alfvén waves
• On the influence of Langmuir wave spectra on the spectra of electromagnetic waves generated in solar plasma with double plasma frequency
• Numerical simulations of a continuously injected relativistic electron beam relaxation into a plasma with large-scale density gradients
• The collisional relaxation of electrons in hot flaring plasma and inferring the properties of solar flare accelerated electrons from X-ray observations