ELECTRON ACCELERATION BY LANGMUIR WAVES PRODUCED BY A DECAY CASCADE

Journal Article · Wed Apr 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/821/2/99· OSTI ID:22863005

Krafft, C. ^[1]

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1. Laboratoire de Physique des Plasmas, Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

It was recently reported that a significant part of the Langmuir waveforms observed by the STEREO satellite during type III solar radio bursts are likely consistent with the occurrence of electrostatic decay instabilities, when a Langmuir wave L resonantly interacts with another Langmuir wave L{sup ′} and an ion sound wave S{sup ′} through the decay channel L→L{sup ′}+S{sup ′}. Usually such wave–wave interactions occur in regions of the solar wind where the presence of electron beams can drive Langmuir turbulence to levels allowing waves L to decay. Moreover, such solar wind plasmas can present long-wavelength, randomly fluctuating density inhomogeneities or monotonic density gradients which can significantly modify the development of such resonant instabilities. If some conditions are met, the waves can encounter a second decay cascade (SDC) according to L{sup ′}→L{sup ′′}+S{sup ′′}. Analytical estimates and observations based on numerical simulations show that the Langmuir waves L{sup ′′} produced by this SDC can accelerate beam particles up to velocities and kinetic energies exceeding two times the beam drift velocity v{sub b} and half the initial beam energy, respectively. Moreover, this process can be particularly efficient if the scattering effects of waves on the background plasma inhomogeneities have already accelerated a sufficient amount of beam electrons up to the velocity range where the phase velocities of the L{sup ′′} waves are lying. The paper shows that the conditions necessary for such process to occur can be easily met in solar wind plasmas if the beam velocities do not exceed around 35 times the plasma thermal velocity.

• OSTI ID: 22863005
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 821; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
COMPUTERIZED SIMULATION
DECAY INSTABILITY
DENSITY
ELECTRON BEAMS
ELECTROSTATICS
INTERACTIONS
LANGMUIR FREQUENCY
PHASE VELOCITY
PLASMA
SATELLITES
SCATTERING
SOLAR RADIO BURSTS
SOLAR WIND
SOUND WAVES
TURBULENCE
WAVE FORMS