Observations of Secondary Magnetic Reconnection in the Turbulent Reconnection Outflow

Abstract

Magnetic reconnection and turbulence are the two most important energy dissipation processes in plasma. These two processes intertwine with each other and play important roles in their respective dynamic evolution. Here, we present the first evidence that secondary reconnections occur in the turbulent outflow driven by a primary reconnection in the Earth's magnetotail. We have identified 14 secondary reconnections in a large number of current filaments in the turbulent outflow, which persisted for about one and half an hour. Most of these secondary reconnections were electron‐only reconnection that has recently been discovered in the magnetosheath. These secondary reconnections entangled the magnetic field lines and dissipated the magnetic energy in the outflow region far away from the primary X line.

Intermittent Dissipation at Kinetic Scales in the Turbulent Reconnection Outflow

“…The reconnection event analyzed in this paper was observed in the Earth's magnetotail plasma sheet at [−19.3, −11.8, 0.8] Re (Re is the Earth's radius) in the GSM coordinates from 03:50 to 05:28 UT on 28 May 2017. This event was first investigated by Zhou et al (2021). One can see that there is a plasma flow reversal from tailward (negative V ix in Figure 1b) to earthward (positive V ix ) around 03:58 UT accompanied by the sign change of B z from negative to positive (Figure 1a), indicating that the MMS crossed a tailward retreating X-line.…”

Electron‐Only Reconnection as a Transition Phase From Quiet Magnetotail Current Sheets to Traditional Magnetotail Reconnection

“…reported a reconnecting current sheet in Earth's turbulent magnetosheath that lacked the ion energization and outflow present around a typical EDR (Phan et al., 2018; Stawarz et al., 2019). This phenomenon, dubbed “electron‐only” reconnection, has since been observed in other regions of Earth's magnetosphere, including the magnetopause (Zhou et al., 2017), bow shock (Gingell et al., 2019), and magnetotail (Man et al., 2018; Wang et al., 2018; Zhou et al., 2021). These observations sparked numerous simulation efforts to learn more about the driving mechanism and plasma/field conditions required for electron‐only reconnection to occur.…”

“…First, traditional magnetotail reconnection during storm times has been shown to generate a turbulent outflow region. This turbulence can entangle magnetic field lines and generate sub-ion scale reconnection that violates the frozen-in condition and forms electron-only outflow jets (Lapenta et al, 2018;Vega et al, 2020;Zhou et al, 2021). Second, Earthward-traveling plasmoids generated by multiple reconnecting X-lines can reconnect with dipolarized tail field (Vogiatzis et al, 2011) and form a current sheet whose aspect ratio is ripe for electron-only reconnection (Man et al, 2018(Man et al, , 2020.…”

Mesoscale Structure in the Solar Wind

“…For example, as described in Section 2, there is a population of insitu detected magnetic flux ropes that have been observed simultaneously in white light that are unambiguously formed at the helmet streamer tip through reconnection and advect along the HCS. But the population of all flux ropes in the solar wind, including those at the HCS, could also be due to turbulence (Cartwright and Moldwin, 2008;Cartwright and Moldwin, 2010;Zheng and Hu, 2018;Zhou et al, 2021), and there is evidence that both populations of flux ropes exist in the inner heliosphere (Murphy et al, 2020). Active reconnection is observed to be taking place far out into the solar wind (Gosling and Szabo, 2008), and reconnection across the HCS is very prevalent close to the Sun (Phan et al, 2021), as well as at the boundaries of switchbacks (Froment et al, 2021).…”