The Effects of Upper‐Hybrid Waves on Energy Dissipation in the Electron Diffusion Region

• Published in: Geophysical research letters 2020-10, Vol.47 (19), p.e2020GL089778-n/a
• Main Authors: Dokgo, Kyunghwan, Hwang, Kyoung‐Joo, Burch, James L., Yoon, Peter H., Graham, Daniel B., Li, Wenya
• Format: Article
• Language: English
• Subjects: Activation; Diffusion; Electric field; Electric fields; Electron diffusion; Electron Diffusion Region; Electrons; Energy Dissipation; Energy exchange; Ionosphere; Kinetic Waves and Instabilities; Magnetic Reconnection; Magnetospheres; Magnetospheric Physics; Mathematical analysis; Parameters; Particle interactions; Plasma; Plasma Energization; Plasma Waves and Instabilities; Profiles; Radio Science; Research Letter; Research Letters; Simulation; Solar Physics, Astrophysics, and Astronomy; Space Plasma Physics; Space Sciences; Spacecraft; Tensors; Upper-Hybrid Waves; Wave/Particle Interactions; Waves in Plasma
• ISSN: 0094-8276; 1944-8007; 1944-8007
• DOI: 10.1029/2020GL089778

Using a two‐dimensional particle‐in‐cell simulation, we investigate the effects and roles of upper‐hybrid waves (UHW) near the electron diffusion region (EDR). The energy dissipation via the wave‐particle interaction in our simulation agrees with J · E′ measured by magnetospheric multiscale (MMS) spacecraft. It means that UHW contributes to the local energy dissipation. As a result of wave‐particle interactions, plasma parameters which determine the larger‐scale energy dissipation in the EDR are changed. The y‐directional current decreases while the pressure tensor Pyz increases/decreases when the agyrotropic beam density is low/high, where (x, y, z)‐coordinates correspond the (L, M, N)‐boundary coordinates. Because the reconnection electric field comes from −∂Pyz/∂z, our result implies that UHW plays an additional role in affecting larger‐scale energy dissipation in the EDR by changing plasma parameters. We provide a simple diagram that shows how the UHW activities change the profiles of plasma parameters near the EDR comparing cases with and without UHW. Plain Language Summary The crescent‐shaped agyrotropic electrons are one of the crucial signatures of the electron diffusion region (EDR) of magnetic reconnection. The magnetospheric multiscale (MMS) mission has revealed that the agyrotropic electrons generate strong s (UHW) near the EDR. Because UHW can energize electrons very efficiently, UHW is believed to play an important role during the magnetic reconnection. In this letter, we investigate the energy dissipation by UHW using a two‐dimensional particle‐in‐cell simulation. We found that UHW contributes to the local energy dissipation process via interactions between UHW and electrons, which is confirmed upon comparing with MMS observation. Our simulation shows that plasma parameters—that is, pressure tensors, current, and electric field—are changed as a result of UHW activities. Such changes in the plasma parameter imply that UHW activities can affect a larger‐scale energy dissipation process in the EDR. Key Points Upper‐hybrid waves locally contribute to the energy dissipation in the electron diffusion region via wave‐particle interaction Pressure tensors, electric field, and current in the EDR can be changed as a result of upper‐hybrid wave activities Changes in the profiles of the plasma parameters can affect larger‐scale energy conversion in the EDR