Plasma Sources in Planetary Magnetospheres: Mercury

Raines, J. M.; DiBraccio, G. A.; Cassidy, Timothy A.; Delcourt, Dominique; Fujimoto, M.; Jia, Xianzhe; Mangano, V.; Milillo, A.; Sarantos, M.; Slavin, J. A.; Würz, Peter

doi:10.1007/s11214-015-0193-4

Cited by 41 publications

(41 citation statements)

References 211 publications

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“…Such events, or ones similar to them, have been noted previously by Raines et al (2015), , Slavin et al (2019), and Winslow et al (2019), but not analyzed in detail beyond noting their presence in the MESSENGER data set. Such events, or ones similar to them, have been noted previously by Raines et al (2015), , Slavin et al (2019), and Winslow et al (2019), but not analyzed in detail beyond noting their presence in the MESSENGER data set.…”

Section: Introductionmentioning

confidence: 58%

MESSENGER Observations of Disappearing Dayside Magnetosphere Events at Mercury

et al. 2019

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MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) measurements taken during passes over Mercury's dayside hemisphere indicate that on four occasions the spacecraft remained in the magnetosheath even though it reached altitudes below 300 km. During these disappearing dayside magnetosphere (DDM) events, the spacecraft did not encounter the magnetopause until it was at very high magnetic latitudes, ~66 to 80°. These DDM events stand out with respect to their extremely high solar wind dynamic pressures, Psw ~140 to 290 nPa, and intense southward magnetic fields, Bz ~ −100 to −400 nT, measured in the magnetosheath. In addition, the bow shock was observed very close to the surface during these events with a subsolar altitude of ~1,200 km. It is suggested that DDM events, which are closely associated with coronal mass ejections, are due to solar wind compression and/or reconnection‐driven erosion of the dayside magnetosphere. The very low altitude of the bow shock during these events strongly suggests that the solar wind impacts much of Mercury's sunlit hemisphere during these events. More study of these disappearing dayside events is required, but it is likely that solar wind sputtering of neutrals from the surface into the exosphere maximizes during these intervals.

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Section: Introductionmentioning

confidence: 58%

MESSENGER Observations of Disappearing Dayside Magnetosphere Events at Mercury

et al. 2019

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“…The observations and modeling results presented above have major implications for understanding the space weathering at Mercury, which is believed to be an important contributor to the generation of the planet's tenuous exosphere (e.g., Domingue et al, ; Orsini et al, ; Raines et al, ). One of the crucial questions related to space weathering at Mercury is to what extent the solar wind can reach the planet's surface, which depends on the configuration of the dayside magnetosphere.…”

Section: Discussionmentioning

confidence: 99%

MESSENGER Observations and Global Simulations of Highly Compressed Magnetosphere Events at Mercury

et al. 2019

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We identify and examine all MErcury Surface Space ENvironment, GEochemistry, and Ranging (MESSENGER) crossings of Mercury's dayside magnetopause with magnetospheric field intensities ≥300 nT. The eight such events, which occurred under highly compressed magnetosphere conditions, are analyzed in the identical manner utilized by Slavin et al. (2014, https://doi.org/10.1002/2014JA020319). The results suggest that the eight highly compressed magnetosphere events represent the highest solar wind dynamic pressures for which the MESSENGER's orbit still passed below the magnetopause and provided measurements of the dayside magnetosphere. Using the magnetohydrodynamic model by Jia et al. (2015, https://doi.org/10.1002/2015JA021143) that electromagnetically couples Mercury's interior with its magnetosphere, a series of global simulations are conducted to quantitatively characterize the response of Mercury's magnetosphere to solar wind forcing. Combining the MESSENGER observations with the simulations, we have obtained a consistent picture of how Mercury's dayside magnetospheric configuration is controlled, separately and in combination, by induction‐driven shielding and reconnection‐driven erosion. For solar wind pressures of ∼40–90 nPa, compared with the average ∼10–15 nPa at Mercury's orbit, the shielding effects of induction in Mercury's core in standing‐off the solar wind typically exceed the erosion of the dayside magnetosphere due to reconnection for these events, most of which occurred under low magnetic shear conditions. For high magnetic shear across the magnetopause our simulation predicts that reconnection would dominate. Mercury's effective magnetic moment as inferred from magnetopause standoff distance ranges from 170 to 250 nT−RM3 for these events. These findings are of crucial importance for understanding the space weathering at Mercury and its contribution to the generation of Mercury's exosphere.

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“…Slavin et al 2009Slavin et al , 2010DiBraccio et al 2013;Raines et al 2015). For example, the magnetic reconnection rate is estimated to be ∼0.15 at Mercury, which is nearly an order of magnitude higher than that observed at Earth .…”

Section: <3mentioning

confidence: 96%

“…Therefore, to understand the structure of Mercury's magnetosphere and its response to the solar wind plasma and IMF variations, we need to understand the interaction between the solar wind and Mercury's magnetosphere and distinguish between the contributions from external and internal magnetic sources (e.g. Raines et al 2015;Johnson & Hauck 2016;James et al 2017).…”

Section: <3mentioning

confidence: 99%

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

Fatemi

Poirier

Holmström

et al. 2018

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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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Plasma Sources in Planetary Magnetospheres: Mercury

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Cited by 41 publications

References 211 publications

MESSENGER Observations of Disappearing Dayside Magnetosphere Events at Mercury

MESSENGER Observations of Disappearing Dayside Magnetosphere Events at Mercury

MESSENGER Observations and Global Simulations of Highly Compressed Magnetosphere Events at Mercury

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

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