Excitation Of High-frequency Plasma Waves By Electron Beam And Temperature Anisotropy

High-frequency plasma waves play significant roles in transporting and dissipating the energy at electron scales.The interaction between high-frequency waves and electrons have attracted much attention in the space physics community.Both the electron beam and electron temperature anisotropy are usually observed in planetary space environments and provide the free energy to excite high-frequency plasma waves.Based on the plasma theory and satellite measurements,this paper investigates the dynamic process of high-frequency plasma waves driven by the electron beam and electron temperature anisotropy.Firstly,this paper obtains the analytical expressions of dispersion relations of plasma waves in three-component plasmas including protons,background electrons and electron beams.Based on these expressions,this paper gives comprehensive analyses on six types of the plasma instabilities driven by the electron beam.These theoretical results are used to explain the electromagnetic fluctuations in the Jupiter polar region.We proposed that the upward energetic electron beam can induce the electron beam instability in the Jupiter polar regions,producing electron acoustic/magneto-acoustic waves,which may be responsible for the electromagnetic emission therein.Secondly,using MMS measurements,this paper studies two typical whistler wave events in the Earth's environment,one event in the Earth's outer magnetosphere and the other in the Earth's magnetosheath.Based on the local plasma parameters and plasma kinetic model,this paper identifies that the observed whistler waves mainly result from the electron temperature anisotropy instability.Moreover,we find the electron beam can considerably affect the whistler wave dynamics,e.g.,resulting in the waves propagating against to the magnetic field in the Earth's outer magnetosphere and the counter-propagating waves with different frequencies in the Earth's magnetosheath.Our results show different excitation mechanisms for high-frequency waves in different plasma environments,and these results are helpful for understanding the dynamics of electrons and highfrequency waves therein.