Ion Larmor Radius Effects and the Larmor Electric Field Near the X-line During Magnetopause Reconnection

Magnetosheath and magnetospheric plasma mixing effects play an important role during magnetic reconnection at the Earth's magnetopause. Understanding the signatures of these effects and the physics behind them are important for interpreting Magnetospheric Multiscale (MMS) observations. Using kinetic PIC simulations, we show that effects on the magnetospheric inflow region such as an Earthward pointing electric field (the Larmor electric field), out-of-plane ion flow, and electron temperature anisotropies are associated with the gyration of magnetosheath ions onto magnetospheric fields due to the shift of the flow stagnation point toward the low-density magnetosphere. We find that many of these signatures are localized within ion scales of the x-line (on the order of 15 ion inertial lengths), and therefore these signatures alone cannot be used for determination of the proximity of the electron diffusion region. We will discuss the physics and the scaling of these ion-scale signatures for various inflow conditions. Finally, we will discuss implications of these findings for analysis and interpretation of MMS observations.