MESSENGER Observations of Rapid and Impulsive Magnetic Reconnection in Mercury's Magnetotail

Zhong, Jun; Wei, Yuanhuan; Pu, Z. Y.; Wang, X. G.; Wan, Weixing; Slavin, J. A.; Cao, X.; Raines, J. M.; Zhang, H.; Xiao, Chijie; Du, Aimin; Wang, R. S.; Dewey, R. M.; Chai, Lihui; Rong, Zhaojin; Li, Y.

doi:10.3847/2041-8213/aaca92

Cited by 17 publications

(16 citation statements)

References 41 publications

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“…Mass, energy, and magnetic flux are transported from Mercury's dayside magnetopause to its nightside magnetotail via an Earth-like Dungey cycle (Imber & Slavin, 2017;Slavin et al, 2010). The cycle is completed by the return flow of mass, energy, and flux toward Mercury driven by magnetic reconnection in Mercury's PS (DiBraccio, Slavin et al, 2009;Smith et al, 2017;Sun et al, 2015;Sundberg et al, 2012;Zhong et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Transport of Mass and Energy in Mercury's Plasma Sheet

Poh

Slavin

Jia

et al. 2018

Geophysical Research Letters

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We examined the transport of mass and energy in Mercury's plasma sheet (PS) using MESSENGER magnetic field and plasma measurements obtained during 759 PS crossings. Regression analysis of proton density and plasma pressure shows a strong linear relationship. We calculated the polytropic index γ for Mercury's PS to be ~0.687, indicating that the plasma in the tail PS behaves nonadiabatically as it is transported sunward. Using the average magnetic field intensity of Mercury's tail lobe as a proxy for magnetotail activity level, we demonstrated that γ is lower during active time periods. A minimum in γ was observed at R ~ 1.4 RM, which coincides with previously observed location of Mercury's substorm current wedge. We suggest that the nonadiabatic behavior of plasma as it is transported into Mercury's near‐tail region is primarily driven by particle precipitation and particle scattering due to large loss cone and particle acceleration effect, respectively.

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Section: Introductionmentioning

confidence: 99%

Transport of Mass and Energy in Mercury's Plasma Sheet

Poh

Slavin

Jia

et al. 2018

Geophysical Research Letters

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“…This also correlates with shifts in statistical field distributions (Poh et al, ), dipolarizations (Dewey et al, ), and the distribution of energetic electrons (Baker et al, ) and their precipitation onto the surface (Lindsay et al, ). In addition, Zhong et al () recently reported the first observations of an active reconnection site in Mercury's magnetotail, during which the spacecraft was located ∼0.5 R M dawnward of midnight.…”

Section: Introductionmentioning

confidence: 99%

Evaluating Single‐Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 1. Spatial Distributions of the Neutral Line

et al. 2018

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A simple Monte Carlo model is presented that considers the effects of spacecraft orbital sampling on the inferred distribution of magnetic flux ropes, generated through magnetic reconnection in the magnetotail current sheet. When generalized, the model allows the determination of the number of orbits required to constrain the underlying population of structures: It is able to quantify this as a function of the physical parameters of the structures (e.g., azimuthal extent and probability of generation). The model is shown adapted to the Hermean magnetotail, where the outputs are compared to the results of a recent survey. This comparison suggests that the center of Mercury's neutral line is located dawnward of midnight by 0 3 and that the flux ropes are most likely to be wide azimuthally (∼50% of the width of the Hermean tail). The downtail location of the neutral line is not self‐consistent or in agreement with previous (independent) studies unless dissipation terms are included planetward of the reconnection site; potential physical explanations are discussed. In the future the model could be adapted to other environments, for example, the dayside magnetopause or other planetary magnetotails.

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“…A key signature for identifying active reconnection is the quadrupole Hall magnetic field structure, resulting from ion‐electron decoupling in the ion diffusion region (Sonnerup, 1979). In the reconnection events during orbits 503 and 877 (Zhong et al., 2018, 2020a), the MESSENGER south‐to‐north crossed the tail current sheet and observed a significant positive‐to‐negative bipolar feature in the out‐of‐plane magnetic field component B M with overall negative B N . Another key reconnection feature is the formation of multiple flux rope (FR) structures.…”

Section: Reconnection Events In Mercury's Magnetotailmentioning

confidence: 99%

MESSENGER Observations of Reconnection in Mercury's Magnetotail Under Strong IMF Forcing

et al. 2023

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Magnetic reconnection is a universal fundamental plasma process that alters the topology of magnetic fields and converts magnetic energy into plasma energy (e.g., Lee & Lee, 2020). Similar to Earth, reconnection occurs at Mercury's dayside magnetopause and in the nightside magnetotail current sheet. allowing the input of solar wind energy and driving the global magnetic flux and plasma circulation in the magnetosphere (e.g., Slavin et al., 2021). The strong solar wind driving, weak intrinsic magnetic field (Anderson et al., 2011), and lack of significant ionosphere, combined with relatively small scale of the magnetosphere (e.g., Winslow et al., 2013;Zhong et al., 2015), may result in reconnection at Mercury that differs from that at Earth. Especially, Mercury's magnetosphere is much more responsive to the interplanetary magnetic field (IMF) direction and is more dominated by the effects of reconnection than that of Earth or of the other magnetized planets (Slavin et al., 2009).At Earth, tail reconnection, which is widely considered to be responsible for triggering substorm onset (e.g., Angelopoulos et al., 2008), is preferably initiated on the duskside (e.g., Eastwood et al., 2010;Nagai et al., 2015). Geotail flux rope (FR) and Cluster traveling compression region (TCR) observations show this asymmetry at Earth very clearly (Slavin et al., 2005). They found that FR and TCR events in the near-nightside plasma sheet and lobes, respectively, occur more frequently, and have larger cross sections and higher bulk speeds on the duskside as compared to the dawnside of Earth's magnetotail. These FR and TCR observations favoring reconnection onset and peak intensity on the duskside of the magnetotail are consistent with numerous studies of the cross-tail current sheet showing it to be thinner on the duskside, on average, with increased asymmetry favoring the onset of reconnection just prior to substorms (Artemyev et al., 2016).Mercury's tail current sheet, on average, is also thinner on the duskside than on the dawnside (Poh et al., 2017a;Rong et al., 2018). As thin current sheets are closely associated with the onset of magnetic reconnection, it is expected that the occurrence of reconnection would also be more frequent on the duskside than on the dawnside. Nevertheless, reconnection-related magnetic structures or phenomena, for example, dipolarizations, flux ropes, and energetic electron injections, are more typically observed by the MESSENGER spacecraft on the dawnside than on the duskside (e.g.,

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MESSENGER Observations of Rapid and Impulsive Magnetic Reconnection in Mercury's Magnetotail

Cited by 17 publications

References 41 publications

Transport of Mass and Energy in Mercury's Plasma Sheet

Transport of Mass and Energy in Mercury's Plasma Sheet

Evaluating Single‐Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 1. Spatial Distributions of the Neutral Line

MESSENGER Observations of Reconnection in Mercury's Magnetotail Under Strong IMF Forcing

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