Rising‐Tone Whistler Wave in a Magnetosheath Side Separatrix of Dayside Magnetic Reconnection

Abstract We investigate Magnetospheric Multiscale (MMS) observation of the rising‐tone whistler waves during the magnetopause asymmetric magnetic reconnection on 24 December 2016. The rising‐tone whistler wave propagates toward the electron diffusion region of magnetic reconnection along the magnetic field on the magnetosheath side of the separatrix. The fundamental frequency of the whistler wave is slightly above 0.5 (electron cyclotron frequency) and rises to 1.0 . This study shows that the separatrix can provide favorable conditions for (a) the generation of whistler waves, (b) the frequency chirping of whistler waves, and (c) the local confinement of whistler waves within the narrow separatrix. These rising‐tone whistler waves, generated under such conditions, may contribute to the rapid energization of electrons during the magnetic reconnection.