Abstract
AbstractIn this paper we use the full armament of the MMS (Magnetospheric Multiscale) spacecraft to study magnetic reconnection in the turbulent magnetosheath downstream of a quasi‐parallel bow shock. Contrarily to the magnetopause and magnetotail cases, only a few observations of reconnection in the magnetosheath have been reported. The case study in this paper presents, for the first time, both fluid‐scale and kinetic‐scale signatures of an ongoing reconnection in the turbulent magnetosheath. The spacecraft are crossing the reconnection inflow and outflow regions and the ion diffusion region (IDR). Inside the reconnection outflows D shape ion distributions are observed. Inside the IDR mixing of ion populations, crescent‐like velocity distributions and ion accelerations are observed. One of the spacecraft skims the outer region of the electron diffusion region, where parallel electric fields, energy dissipation/conversion, electron pressure tensor agyrotropy, electron temperature anisotropy, and electron accelerations are observed. Some of the difficulties of the observations of magnetic reconnection in turbulent plasma are also outlined.
Highlights
Magnetic reconnection is almost routinely observed at large-scale boundaries such as the Earth’s magnetopause (e.g., Burch et al, 2016; Paschmann et al, 1979; Phan et al, 2004; Russell & Elphic, 1979) and the magnetotail current sheet (e.g., Nagai et al, 2015; Nakamura et al, 2006; Øieroset et al, 2001; Runov et al, 2003)
In this paper we use the full armament of the MMS (Magnetospheric Multiscale) spacecraft to study magnetic reconnection in the turbulent magnetosheath downstream of a quasi-parallel bow shock
In any case, based on Magnetospheric Multiscale (MMS) observations, here we provide an event study, which can elucidate some important aspects of the observation of fluid- and kinetic-scale signatures of ongoing magnetic reconnection in the terrestrial magnetosheath
Summary
Magnetic reconnection is almost routinely observed at large-scale boundaries such as the Earth’s magnetopause (e.g., Burch et al, 2016; Paschmann et al, 1979; Phan et al, 2004; Russell & Elphic, 1979) and the magnetotail current sheet (e.g., Nagai et al, 2015; Nakamura et al, 2006; Øieroset et al, 2001; Runov et al, 2003). In the Retinò et al (2007) event, the four Cluster spacecraft observed similar profiles of the magnetic field indicating that the ion-scale current sheet was planar or time stationary. A study using MMS data has shown that fast magnetosheath shear flows can locally generate ion-scale current sheets with nonplanar 3-D structure (Eriksson, Vaivads, et al, 2016). Field, and particle signatures were considered by Yordanova et al (2016) as imprints of the crossing of the separatrix region of magnetic reconnection in the QPar magnetosheath, this event does not match fully the exhaust boundary structure of the Phan, Paschmann, et al (2007) event.
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