MESSENGER observations of flux ropes in Mercury’s magnetotail

DiBraccio, G. A.; Slavin, J. A.; Imber, Suzanne M.; Gershman, D. J.; Raines, J. M.; Jackman, C. M.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Zurbuchen, T. H.; McNutt, R. L.; Solomon, Sean C.

doi:10.1016/j.pss.2014.12.016

Cited by 67 publications

(174 citation statements)

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“…For example, flux ropes often last~3 to 5 s [e.g., Slavin et al, 2012;DiBraccio et al, 2015;Sun et al, 2016]. We have averaged the magnetic field with a 40 s sliding window prior to the fitting, aiming to remove the field perturbations commonly observed in Mercury's plasma sheet.…”

Section: Statistical Resultsmentioning

confidence: 99%

“…To study the ion properties in Mercury's magnetotail, Gershman et al [2014] have investigated several tens of premidnight plasma sheet crossings at distances down the tail of~2-3 R M (R M , Mercury radius~2440 km) in the near-Mercury neutral line (NMNL) region [e.g., Slavin et al, 2012;DiBraccio et al, 2015;Poh et al, 2017a]. In that study, ion species (such as, H + , He ++ , and Na + ) in Mercury's plasma sheet display strong kinetic effects.…”

Section: Introductionmentioning

confidence: 99%

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MESSENGER observations of the energization and heating of protons in the near‐Mercury magnetotail

Sun

Raines

et al. 2017

Geophysical Research Letters

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The energization and heating processes for protons in the near‐Mercury tail are examined with MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observations. In a case study, suprathermal proton particle flux (STPF) and proton temperature are observed to be clearly enhanced during near‐Mercury substorm dipolarizations, indicating the proton energization and heating processes. STPF and proton temperature distributions in near‐Mercury central plasma sheets display dawn‐dusk asymmetries, with higher values in the dawnside plasma sheet, i.e., postmidnight, than in the duskside, i.e., premidnight. Further investigations reveal that these asymmetries are more prominent during active periods in Mercury's magnetosphere, as compared to quiet periods. Magnetic field variations in the ZMSM component display a similar feature, with variations being more prominent on the dawnside than the duskside during active periods. We propose that the dawn‐dusk asymmetry in the distributions of protons could be due to the fact that more substorm dipolarizations were initiated on the dawnside of Mercury's magnetotail.

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Section: Statistical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

MESSENGER observations of the energization and heating of protons in the near‐Mercury magnetotail

Sun

Raines

et al. 2017

Geophysical Research Letters

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“…In a recent study of reconnection in Mercury's magnetotail, DiBraccio et al . [] found frequent formation of flux ropes having core fields that are highly skewed with respect to the Y MSM direction but with no systematic pattern indicative of a global tilt. The size of these flux ropes was estimated to be a few H + gyroradii, much smaller than those of Na + ions near the duskside MP, suggesting that whereas gyrating Na + ions may scatter through interaction with these perturbations, it is unlikely that they influence flux rope formation.…”

Section: Discussionmentioning

confidence: 99%

“…However, DiBraccio et al . 's [] study focused on events measured within only ~1 h of local midnight, where the overall variation in Na + content is not high and the number density of Na + in this region is on the order of ~1%.…”

Section: Discussionmentioning

confidence: 99%

MESSENGER observations of multiscale Kelvin‐Helmholtz vortices at Mercury

et al. 2015

Self Cite

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Observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in Mercury's magnetotail demonstrate for the first time that Na + ions exert a dynamic influence on Mercury's magnetospheric system. Na + ions are shown to contribute up to~30% of the ion thermal pressure required to achieve pressure balance in the premidnight plasma sheet. High concentrations of planetary ions should lead to Na + dominance of the plasma mass density in these regions. On orbits with northward-oriented interplanetary magnetic field and high (i.e., >1 cm À3) Na + concentrations, MESSENGER has often recorded magnetic field fluctuations near the Na + gyrofrequency associated with the Kelvin-Helmholtz (K-H) instability.These nightside K-H vortices are characteristically different from those observed on Mercury's dayside that have a nearly constant wave frequency of~0.025 Hz. Collectively, these observations suggest that large spatial gradients in the hot planetary ion population at Mercury may result in a transition from a fluid description to a kinetic description of vortex formation across the dusk terminator, providing the first set of truly multiscale observations of the K-H instability at any of the diverse magnetospheric environments explored in the solar system.

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“…a few seconds flux transfer events (Slavin et al 2012b) and plasmoids (Slavin et al 2012a;DiBraccio et al 2015)) indicate that the magnetosphere of Mercury is highly dynamic, sensitive, and responsive to the solar wind plasma and IMF variations, much more than any other magnetized planet in the solar system (Burlaga 2001;Slavin et al 2008Slavin et al , 2009). Solar wind variations contribute considerably to altering the structure of Mercury's magnetosphere (e.g.…”

Section: <3mentioning

confidence: 99%

A modelling approach to infer the solar wind dynamic pressure from magnetic field observations inside Mercury’s magnetosphere

Fatemi

Poirier

Holmström

et al. 2018

A&A

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Aims. The lack of an upstream solar wind plasma monitor when a spacecraft is inside the highly dynamic magnetosphere of Mercury limits interpretations of observed magnetospheric phenomena and their correlations with upstream solar wind variations. Methods. We used AMITIS, a three-dimensional GPU-based hybrid model of plasma (particle ions and fluid electrons) to infer the solar wind dynamic pressure and Alfvén Mach number upstream of Mercury by comparing our simulation results with MESSENGER magnetic field observations inside the magnetosphere of Mercury. We selected a few orbits of MESSENGER that have been analysed and compared with hybrid simulations before. Then we ran a number of simulations for each orbit (∼30-50 runs) and examined the effects of the upstream solar wind plasma variations on the magnetic fields observed along the trajectory of MESSENGER to find the best agreement between our simulations and observations. Results. We show that, on average, the solar wind dynamic pressure for the selected orbits is slightly lower than the typical estimated dynamic pressure near the orbit of Mercury. However, we show that there is a good agreement between our hybrid simulation results and MESSENGER observations for our estimated solar wind parameters. We also compare the solar wind dynamic pressure inferred from our model with those predicted previously by the WSA-ENLIL model upstream of Mercury, and discuss the agreements and disagreements between the two model predictions. We show that the magnetosphere of Mercury is highly dynamic and controlled by the solar wind plasma and interplanetary magnetic field. In addition, in agreement with previous observations, our simulations show that there are quasi-trapped particles and a partial ring current-like structure in the nightside magnetosphere of Mercury, more evident during a northward interplanetary magnetic field (IMF). We also use our simulations to examine the correlation between the solar wind dynamic pressure and stand-off distance of the magnetopause and compare it with MESSENGER observations. We show that our model results are in good agreement with the response of the magnetopause to the solar wind dynamic pressure, even during extreme solar events. We also show that our model can be used as a virtual solar wind monitor near the orbit of Mercury and this has important implications for interpretation of observations by MESSENGER and the future ESA/JAXA mission to Mercury, BepiColombo.

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MESSENGER observations of flux ropes in Mercury’s magnetotail

Cited by 67 publications

References 59 publications

MESSENGER observations of the energization and heating of protons in the near‐Mercury magnetotail

MESSENGER observations of the energization and heating of protons in the near‐Mercury magnetotail

MESSENGER observations of multiscale Kelvin‐Helmholtz vortices at Mercury

A modelling approach to infer the solar wind dynamic pressure from magnetic field observations inside Mercury’s magnetosphere

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