Abstract: Petschek’s model of reconnection has a reconnection rate comparable to in-situ observations. In this model, the small diffusion region is flanked by two slow-mode shocks on each side of the exhaust. This study explores the existence of slow-mode shocks in magnetic reconnection with both 2.5 D hybrid simulations and Magnetospheric MultiScale (MMS) observations. We use the six Rankine-Hugoniot conditions and six specific conditions for slow-mode shocks to analyze the presence of slow-mode shocks. We observe that the reconnection boundary can be interpreted as a slow-mode shock from as close as ~9 ion inertial lengths from the X-point. The detection of slow-mode shocks increases with increasing distance from the X-point and with increasing ion plasma beta. The change in beta leads to the change in turbulence, thus causing a decrease in the detection of slow-mode shocks as the turbulence increases. When the crossings become more symmetric, i.e., the number density on either side of reconnection boundaries becomes similar, more slow-mode shocks are observed. In the near-Earth magnetotail crossings of MMS, 21 out of 51 crossings showed slow-mode shock signature, and in the dayside Magnetopause, 20 out of 99 crossings were observed to have slow-mode shocks. For the crossings where the interface was not identified as a slow-mode shock, it was found that the wavy structure of turbulence in those crossings can change the mass flux values and disrupt the detection of slow-mode shock at those particular locations. However, the macroscopic slow-mode shock-like structure stably exists around the magnetic reconnection interface as most of the conditions for slow-mode shocks are satisfied when slow-mode shocks are not observed. This result suggests that slow-mode shocks are a general feature of magnetic reconnection geometry as is expected from Petschek’s reconnection theory.
Hosted by Jeffersson A. Agudelo Rueda & Professor Yi-Hsin Liu
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