Studying Dawn‐Dusk Asymmetries of Mercury's Magnetotail Using MHD‐EPIC Simulations

Chen, Yuxi; Tóth, G.; Jia, Xianzhe; Slavin, J. A.; Sun, W.; Markidis, Stefano; Gombosi, T. I.; Raines, J. M.

doi:10.1029/2019ja026840

Cited by 30 publications

(49 citation statements)

References 69 publications

(171 reference statements)

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“…Two models are used in this study: the Hall MHD (Tóth et al., 2008) model with electron pressure equation and the semiimplicit particle‐in‐cell kinetic model iPIC3D (Chen & Toth 2019; Markidis et al., 2010). These two models are coupled together through SWMF and form the MHD‐EPIC fluid‐kinetic model (Daldorff et al., 2014) that has been successfully applied to Mercury (Chen et al., 2019), Earth (Chen et al., 2017), Mars (Ma et al., 2018), and Ganymede (Tóth et al., 2016; Zhou et al., 2019).…”

Section: Model Descriptionmentioning

confidence: 99%

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

et al. 2020

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The largest moon in the solar system, Ganymede, is the only moon known to possess a strong intrinsic magnetic field and a corresponding magnetosphere. Using the latest version of Space Weather Modeling Framework (SWMF), we study the upstream plasma interactions and dynamics in this sub‐Alfvénic system. Results from the Hall magnetohydrodynamics (MHD) and the coupled MHD with embedded particle‐in‐cell (MHD‐EPIC) models are compared. We find that under steady upstream conditions, magnetopause reconnection occurs in a nonsteady manner, and the energy partition between electrons and ions is different in the two models. Flux ropes of Ganymede's radius in length form on the magnetopause at a rate about 3 min and create spatiotemporal variations in plasma and field properties. Upon reaching proper grid resolutions, the MHD‐EPIC model can resolve both electron and ion kinetics at the magnetopause and show localized nongyrotropic behavior inside the diffusion region. The estimated global reconnection rate from the models is about 80 kV with 60% efficiency, and there is weak evidence of ∼1 min periodicity in the temporal variations due to the dynamic reconnection process.

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Section: Model Descriptionmentioning

confidence: 99%

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

et al. 2020

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“…The plasma sheet is thicker on the dawnside than on the duskside (Poh et al, 2017a), and magnetic reconnection occurs more frequently on the dawnside plasma sheet (Sun et al, 2016). The heavy ions are found to be concentrated on the duskside plasma sheet, that is, the pre‐midnight sector (Gershman et al, 2014; Raines et al, 2011), whereas there are more protons on the dawnside than on the duskside (Chen et al, 2019; Korth et al, 2014). In studies about the dawn‐dusk asymmetry of Mercury's magnetotail, Korth et al (2014) investigated the distribution of proton fluxes, and Chen et al (2019) presented the proton momenta under the assumption of isotropic and Gaussian distributions (Gershman et al, 2013; Raines et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Proton Properties in Mercury's Magnetotail: A Statistical Study

Zhao

Zong

Slavin

et al. 2020

Geophysical Research Letters

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This study investigates the properties of protons in the magnetotail plasma sheet of Mercury. By superposing 5-year measurements from the MESSENGER spacecraft, we obtain the average energy spectrum of protons in the plasma sheet, which can be fitted nicely by the Gaussian-Kappa model. The proton density, pressure, and energy spectral index are found to be higher on the dawnside than on the duskside. The proton temperature shows a clearly outward radial gradient. The field-aligned density profile indicates that the protons in the outer plasma sheet move adiabatically. The pitch angle distribution reveals the reflected fluxes to be always less than the incident fluxes and indicates the loss of protons due to their impact on the planetary surface. Plain Language Summary Mercury has a miniature magnetosphere subject to intense solar wind forcing. This magnetosphere, among the smallest in the solar system, resembles the Earth's in many key respects. It is also an analog for other small and outside-driven magnetospheres, such as Ganymede's inside Jupiter's magnetosphere. Mercury does not have a significant atmosphere but a tenuous exosphere. Therefore, Mercury's magnetospheric ions are thought to come predominately from the solar wind, and only about 10% of the ions are of planetary origin. This study presents a statistical picture of the protons in Mercury's magnetotail plasma sheet measured by the Fast Imaging Plasma Spectrometer (FIPS) onboard MESSENGER spacecraft. Many parameters are obtained through a best fit procedure with a Gaussian-Kappa distribution. The proton number density, proton pressure, and spectral index show clear dawn-dusk asymmetric features. The results also suggest that the motion of the protons is adiabatic in the outer plasma sheet and non-adiabatic in the central plasma sheet. Furthermore, the loss feature of the protons is also revealed by their asymmetric pitch angle distributions.

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“…Interestingly, the observed dawn-dusk asymmetric distribution of current sheet flapping wave occurrence in Mercury's cross-tail current sheet is also similar to the spatial distribution of sodium ion (Na + ) density as shown in Figures 5a and 5c. Previous MESSENGER studies using the Fast Imaging Plasma Spectrometer (FIPS) instrument (Raines et al, 2013;Gershman et al, 2014) reported higher observed Na + density in the premidnight (or duskside) region of Mercury's plasma sheet, and this dawn-dusk Na + density asymmetry has also been observed in simulations (e.g., Chen et al, 2019;Yagi et al, 2017). Such dawn-dusk asymmetry in Na + density has been associated with the Na + dynamics in Mercury's magnetosphere, such as escape of Na + from a high-energy partial sodium ring during high solar wind dynamic pressure condition (Yagi et al, 2010(Yagi et al, , 2017 or centrifugal acceleration and transport of cold Na + from Mercury's cusp into the duskside plasma sheet via nonadiabatic Speiser-type orbits (Delcourt, 2013).…”

Section: Journal Of Geophysical Research: Space Physicsmentioning

confidence: 85%

“…Although the structure and processes occurring in Mercury's magnetotail are known to be qualitatively similar to that of Earth's, they are different in spatial and temporal scale (e.g., Gershman et al, 2014;Poh et al, 2017b;Raines et al, 2011;Sun et al, 2015). Recent simulation studies (Chen et al, 2019;Liu et al, 2019) suggest that kinetic-scale dynamics and instabilities dominate in Mercury's small magnetotail (~10 d i wide, where d i is the ion inertial length), thereby explaining the observed asymmetric structure and occurrence of processes in the tail.…”

Section: Introductionmentioning

confidence: 99%

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Large‐Amplitude Oscillatory Motion of Mercury's Cross‐Tail Current Sheet

et al. 2020

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We surveyed 4 years of MESSENGER magnetic field data and analyzed intervals with observations of large‐amplitude oscillatory motions of Mercury's cross‐tail current sheet, or flapping waves, characterized by a decrease in magnetic field intensity and multiple reversals of BX, oscillating with a period on the order of ~4 – 25 seconds. We performed minimum variance analysis (MVA) on each flapping wave event to determine the current sheet normal. Statistical results showed that the flapping motion of the current sheet caused it to warp and tilt in the y‐z plane, which suggests that these flapping waves are kink‐type waves propagating in the cross‐tail direction of Mercury's magnetotail. The occurrence of flapping waves shows a strong preference in Mercury's duskside plasma sheet. We compared our results with the magnetic double‐gradient instability model and examined possible flapping wave excitation mechanism theories from internal (e.g., finite gyroradius effects of planetary sodium ions Na+ on magnetosonic waves) and external (e.g., solar wind variations and K‐H waves) sources.

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Studying Dawn‐Dusk Asymmetries of Mercury's Magnetotail Using MHD‐EPIC Simulations

Cited by 30 publications

References 69 publications

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

Proton Properties in Mercury's Magnetotail: A Statistical Study

Large‐Amplitude Oscillatory Motion of Mercury's Cross‐Tail Current Sheet

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