Beam-driven Lower hybrid wave Nonlinear saturation and Turbulence in the
Magnetopause
Abstract
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The proposed work presents a model to understand the lower hybrid
turbulence as observed by the Magnetospheric Multiscale (MMS) mission in
the magnetic reconnection regions of magnetopause by the energetic
electron beams (generated by the magnetic reconnection process). The
magnetic reconnection process has been substituted by the “energetic
electron beam source” in this model. Therefore, in the proposed model,
dynamical equations for beam-driven lower hybrid wave (LHW) have been
formulated, foreseeing that it will evolve from noise level and then
attain large amplitude due to beam energy. At large amplitude,
non-linear effects due to ponderomotive force dominate, causing LHW
localization and the turbulent state. A non-linear two-dimensional model
with the help of the two-fluid dynamics has been developed. The present
mathematical model considers the interaction between pump LHW and low
frequency magnetosonic wave (MSW). The MSW, present in the background,
has been contemplated as the source of density perturbations in LHW
dynamics. The LHW is the source of ponderomotive nonlinearity in the
medium and is incorporated in the MSW wave dynamics. With the help of
the growth term associated with the electron beam, dynamical equations
for LHW and MSW have been established. The two coupled equations, thus
obtained, were solved with the help of numerical simulation techniques.
The results show the temporal evolution of the LHW from noise level and
formation of localized structures and turbulence consistent with MMS
mission observations.