Abstract
Lower hybrid waves are investigated at the magnetosheath separatrix
region in asymmetric guide-field reconnection by using the
Magnetospheric Multiscale (MMS) mission. Three of the four MMS
spacecraft observe clear wave activities around the lower hybrid
frequency across the magnetosheath separatrix, where a density gradient
is present. The observed waves are consistent with generation by the
lower hybrid drift instability. The characteristic properties of these
waves include: (1) the waves propagate toward the x-line in the
spacecraft frame due to the large out-of-plane magnetic field, which is
in the same direction of the diamagnetic drift of the x-line; (2) the
wave potential is about 20\% of the electron
temperature. These drift waves effectively produce cross-field particle
diffusion, enabling the transport of magnetosheath electrons into the
exhaust region. The observations presented in this study indicate unique
features of asymmetric guide-field reconnection.