Maps
Webmail
Home > About us > Media > Archived news > 2022 > Electromagnetic emissions at fundamental and harmonic plasma frequencies by an electron beam in a randomly inhomogeneous solar wind plasma
Electromagnetic emissions at fundamental and harmonic plasma frequencies by an electron beam in a randomly inhomogeneous solar wind plasma
All the versions of this article: [English] [français]
During type III solar bursts, electron beams accelerated to high energies propagate in the solar corona and wind, generating electromagnetic emissions at the plasma frequency ωp and its harmonic 2ωp, both observed in the vicinity of the Earth and in the solar wind, as recently by the Parker Solar Probe and Solar Orbiter missions. They result from a series of linear and non-linear phenomena where Langmuir wave turbulence generated by electron beams as well as wave-wave, wave-particle and wave-plasma interactions play an essential role. However, the physical mechanisms involved are far from being elucidated to date, partly because of the random density fluctuations that characterize actual solar wind plasmas and crucially modify the predictions of existing theoretical models, developed for homogeneous plasmas.
Two-dimensional (2D) Particle-In-Cell (PIC)numerical simulations have investigated the electromagnetic radiation emitted at the fundamental plasma frequency ωp by an electron beam propagating in a solar wind plasma characterized by random density fluctuations, under physical conditions typical of type III solar bursts (Krafft and Savoini, APJL, 917:L23, 2021, Krafft and Savoini, APJL, 924:L24, 2022) Wave, beam, and plasma dynamics are computed over several thousand plasma periods ωp-1, for the cases of a homogeneous plasma and an inhomogeneous plasma with density fluctuations of the order of 5%. These 2D-PIC simulations, performed under strong physical and numerical constraints (high spatial and temporal resolutions and realistic physical conditions), are a real challenge considering the results obtained so far in the literature. For the first time, the essential impact of the random fluctuations of density of a few percent inherent to solar wind plasmas on the physical mechanisms governing the electromagnetic radiation at frequency ωp is demonstrated and characterized. The obtained results show that not only the nonlinear wave interactions but also the processes of wave transformations forming Langmuir turbulence on the fluctuations of density (reflection, refraction, scattering, tunneling, conversion, localization, self-organization), contribute consistently to the generation of the emissions at frequency ωp.
During beam relaxation, the amount of electromagnetic energy radiated at frequency ωp in a randomly inhomogeneous plasma (Krafft and Savoini, APJL, 924:L24, 2022) strongly exceeds that observed when the plasma is homogeneous. Moreover, the fraction of Langmuir wave energy involved in the generation of electromagnetic emission at ωp saturates around 10-4, i.e., an order of magnitude above that achieved when the plasma is homogeneous. While the emission at 2ωp always exceeds the fundamental emission at ωp in a homogeneous plasma, the latter is largely dominant when the plasma contains random fluctuations of density, at least for several thousand ωp-1 plasma periods before being dominated by the emission at 2ωp when the total electromagnetic energy saturates. For the first time the crucial role played by solar wind density fluctuations in the wave-wave and wave-matter interaction mechanisms behind the transformations of Langmuir wave turbulence generated by a particle beam into electromagnetic radiation during type III radio solar bursts has been demonstrated.
Electromagnetic waves emitted at the frequency 2ωp (Krafft and Savoini, APJL, 917:L23, 2021), are produced by nonlinear processes of coalescence between two Langmuir waves, despite the interactions of these waves with density fluctuations that strongly affect their spectral distributions; asymptotically, they exhibit isotropic spectra whereas quadrupolar radiation is observed in homogeneous plasma. The fraction of the initial beam energy transferred to them is an order of magnitude smaller than in the case of a homogeneous plasma, while the ratio of their energy to the energy carried by the Langmuir wave turbulence is notably higher during the entire nonlinear phase.
Also in this section :
- 2022 Summer School for undergraduate students: From the laboratory to the distant universe, the World of Plasmas
- Henri Decauchy defended his PhD "Physics of cold plasma jets - Fundamental study of guided streamers and applications to oncology"
- Lui Habl defended his PhD "Investigation of DC and RF biased gridded ion thruster plume phenomena"
- Review on physics of plasma jets and interaction with surfaces
- Pascal Chabert receives the Silver Medal from CNRS
- Giulia Cozzani, former Ph.D. student at LPP, has been awarded with the Vincenzo Ferraro Prize 2022
- Audrey Chatain has been awarded the 2021 René Pellat prize from SFP (French Physics Society)
- The first international symposium on CO2 recycling by plasma/catalysis closes the H2020 PIONEER project
- A competition for the spontaneous rotation of the plasma
- Public outreach conference on the Solar Orbiter mission and the Sun’s influence on Earth at the Plaisir Castle park
- Non Thermal Plasmas for in situ resources utilization (ISRU) in Mars missions
- Science Festival 2022
- Jean-Paul Booth receives the 2019 Plasma Prize Award of the American Vacuum Society
- Océane Blaise defended her PhD "Cold atmospheric plasma improves bactericidal activity and stimulates phagosome maturation of macrophages"
- Robin Varennes defended his PhD "Flow drive in tokamak plasmas: competition and synergies between turbulence and neoclassical effects"
- Benjamin Esteves defended his "Investigation of iodine plasmas for space propulsion applications"
- Jonas August defended his PhD "Etude des effets d’un plasma froid d’air ambiant sur la physiologie des graines d’Arabidopsis"
- Soboh Alqeeq defended his PhD "Energy conversion processes related to dipolarization fronts in the Earth magnetotail"
- Nicolas Aunai defended his HDR «Studying magnetic reconnection via modeling and observations in the Earth magnetosphere »
- Opening of applications for the Master M2 of Physics of Plasmas and Fusion
