The Role of Accelerated Electron Beams in the Generation of Intense Current Structures and Nonideal Electric Fields in the Outer Region of the Plasma Sheet

We report Magnetospheric Multiscale Mission (MMS) observations of accelerated field-aligned electron beams in the outer ( $$\left| {{{B}_{x}}} \right| \sim \left( {10{\kern 1pt} - {\kern 1pt} 20} \right)\,\,{\text{nT}}$$ ) regions of the Plasma Sheet (PS). The MMS satellites were located earthward of the magnetic reconnection X-line, inside of the bursty bulk flow. The interval corresponds to the growth phase of the substorm. Field-aligned electron beams was produced by electrons suprathermal population with energy $$ \sim {\kern 1pt} \left( {1{\kern 1pt} - {\kern 1pt} 5} \right)\,\,{\text{keV}}$$ . Newly accelerated electron beams are gyrotropic. In the process of evolution, agyrotropy of the beam develops. This leads to the generation of intense (up to ∼80 nA/m2) field-aligned currents. We demonstrate that acceleration of the electrons is pulsed for the time $$ < {\kern 1pt} 5\,\,~{\text{s}}$$ . Propagation of the high-velocity electron beam results in the development of plasma instabilities and generation of a strong (∼59 mV/m) nonideal electric field at frequencies lower than electron cyclotron frequency $${{{{\omega }}}_{{c,e}}}$$ . The presence of a nonideal electric field leads to the violation of the frozen-in condition of electron plasma and energy dissipation. The energy transformation power density reaches ∼–1000 pW/m3. Fluctuations in the spectrum of a nonideal electric field experience spectral flattering between ion plasma $${{{{\omega }}}_{{p,i}}}$$ and electron cyclotron $${{{{\omega }}}_{{c,e}}}$$ frequencies. This evidences energy transfer from particles to waves at this spectral range. The studied phenomena may provide significant contributions to the development of turbulence on electronic kinetic scales in the outer region of the PS.