Vlasov simulations of electron acceleration by radio frequency heating near the upper hybrid layer

A. Najmi, B. Eliasson, X. Shao, G. Milikh, A. S. Sharma, K. Papadopoulos

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Abstract

It is shown by using a combination of Vlasov and test particles simulations that the electron distribution function resulting from energization due to Upper Hybrid (UH) plasma turbulence depends critically on the closeness of the pump wave to the double resonance, defined as omega≈omega_UH≈n omega_ce where n is an integer. For pump frequencies, away from the double resonance the electron distribution function is very close to Maxwellian, while as the pump frequency approaches the double resonance it develops a high energy tail. The simulations show turbulence involving coupling between Lower Hybrid (LH) and UH waves, followed by excitation of Electron Bernstein (EB) modes. For the particular case of a pump with frequency between n=3 and n=4 the EB modes cover the range from the first to the 5th mode. The simulations show that when the injected wave frequency is between the 3rd and 4th electron cyclotron frequency, bulk electron heating occurs due to the interaction between the electrons and large amplitude EB waves, primarily on the first EB branch leading to an essentially thermal distribution. On the other hand, when the frequency is slightly above the 4th electron cyclotron harmonic, the resonant interaction is predominantly due to the UH branch and leads to a further acceleration of high-velocity electrons and a distribution function with a suprathermal tail of energetic electrons. The results are consistent with ionospheric experiments and relevant to the production of Artificial Ionospheric Plasma Layers.
Original languageEnglish
Article number102904
Number of pages12
JournalPhysics of Plasmas
Volume24
Issue number10
DOIs
Publication statusPublished - 26 Oct 2017

Keywords

  • ionospheric heating
  • upper hybrid waves
  • Bernstein waves
  • stochastic heating

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