Observations of Whistler Waves in the Magnetic Reconnection Diffusion Region

Abstract

W2018ATRASCHuang. In this paper, we report the simultaneous occurrence of two types of the whistler waves in the magnetotail reconnection diffusion region. The first type is observed in the pileup region of downstream and propagates away along the field lines to downstream, and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type is found around the separatrix region and propagates towards the X-line, and is possibly generated by the electron beam-driven whistler instability or Ccrenkov emission from electron phase-space holes. Our observations of two different types of whistler waves are well consistent with recent kinetic simulations, and suggest that the observed whistler waves are the consequences of magnetic reconnection. Moreover, we statistically investigate the whistler waves in the magnetotail reconnection region, and construct the global distribution and occurrence rate of the whistler waves based on the two-dimensional reconnection model. It is found that the occurrence rate of the whistler waves is large in the separatrix region ( $\vert B_{\text{x}}/B_{0}\vert >0.4$ ) and pileup region $(\vert B_{\text{x}}/B_{0}\vert 45^{\circ})$ , but very small in the X-line region. The statistical results are well consistent with the case study.