The Effects of Upper-Hybrid Waves on Energy Conversion in the Electron Diffusion Region

Abstract:

Recently, the Magnetospheric Multiscale Mission (MMS) found that the agyrotropic electrons in the electron diffusion region (EDR) can generation upper-hybrid waves (UHW). It is believed that UHW play a significant role by heating electrons via the wave-particle interaction. Using a 2-dimensional Particle-in-Cell simulation (PIC), we investigate the effects and roles of UHW on the energy conversion process near the EDR.

We found that there are two effects of UHW. The first one is the local energy conversion and electron heating via the wave-particle interaction. The local energy conversion rate J·E measured by MMS in the July 3^rd, 2017 event agrees with the heating rate in the PIC simulation. The other is that the UHW can change the large-scale energy conversion J_y·E_y in the EDR. The simulation result shows that the plasma quantities, such as pressure tensor, current, and the reconnection electric field, are changed as a result of UHW activities. The current J_y decreases, and the pressure tensor P_yz increases/ decreases when the beam density is lower/ higher than 13% of total density. When the beam density is 30% of the total density, J_y decreases by at most 5% from the initial value, and P_yz decreases by 26%. Considering the gradient of the pressure tensor generates the reconnection electric field, which is a dominant term in the EDR, our results mean that UHW can change the global profile of energy conversion J_y·E_y in the EDR.