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Pre-flight Calibration and Near-Earth Commissioning Results of the Mercury Plasma Particle Experiment (MPPE) Onboard MMO (Mio)

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BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was successfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020 following the completion of the low voltage commissioning in November 2018. Although all of the MPPE analyzers are now ready to begin observation, the full service performance has been delayed until Mio’s arrival at Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters, MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury when BepiColombo/Mio begins observation after arriving at the planet Mercury in December 2025.
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Space Science Reviews (2021) 217:70
https://doi.org/10.1007/s11214-021-00839-2
Pre-flight Calibration and Near-Earth Commissioning Results
of the Mercury Plasma Particle Experiment (MPPE) Onboard
MMO (Mio)
Yoshifumi Saito ·Dominique Delcourt·Masafumi Hirahara·Stas Barabash·
Nicolas André·Takeshi Takashimaet al. [full author details at the end of the article]
Received: 17 June 2020 / Accepted: 19 June 2021 / Published online: 29 July 2021
© The Author(s), under exclusive licence to Springer Nature B.V. 2021
Abstract
BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was suc-
cessfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The
Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package on-
board Mio spacecraft used for plasma, high-energy particle and energetic neutral atom mea-
surements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1
and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy
Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-
ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to
calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage
commissioning of MPPE analyzers was successfully performed between June and August
2019 and in February 2020 following the completion of the low voltage commissioning in
November 2018. Although all of the MPPE analyzers are now ready to begin observation,
the full service performance has been delayed until Mio’s arrival at Mercury. Most of the
fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surround-
ing the Mio spacecraft during the cruising phase. Together with other instruments on Mio
including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that
measure plasma field parameters, MPPE will contribute to the comprehensive understand-
The BepiColombo mission to Mercury
Edited by Johannes Benkhoff, Go Murakami and Ayako Matsuoka
BepiColombo Mio/MPPE Team: Y. Saito, M. Hirahara, S. Barabash, D. Delcourt, A. Coates, N. André,
T. Takashima, K. Asamura, C. Aoustin, J.-A. Sauvaud, P. Louarn, M. Blanc, C. Jacquey, C. Mazelle,
I. Dandouras, V. Genot, D. Toublanc, C. Peymirat, A. Fedorov, E. Amata, R. Bruno, M.B. Cattaneo,
G. Consolini, M.F. Marcucci, Z. N˘
eme˘
cek, B. Lavraud, L. Griton, S. Aizawa, H.-C. Seran, J. Rouzaud,
Q.M. Lee, E. Le Comte, E. Penou, M. Petiot, D. Moirin, S. Machida, I. Shinohara, W. Miyake,
T. Terasawa, C. Owen, A. Fazakerley, T. Nagatsuma, K. Seki, T. Nagai, A. Ieda, H. Hasegawa,
J.-M. Illiano, J.-J. Berthelier, D. Fontaine, N. Krupp, J. Woch, S. Yokota, M. Fraenz, H. Krueger,
H. Michalik, L. Hadid, R. Modolo, B. Fiethe, B. Katra, F. Leblanc, C. Verdeil, H. Fischer, J.-D. Techer,
D. Reisenfeld, R. Elphic, H. Funsten, D. McComas, M. Grande, H. Matsumoto, T. Yanagimachi,
T. Obara, Y. Miyoshi, Y. Ebihara, M. Nose, F. Tsuchiya, T.A. Fritz, Q. Zong, T. Mitani, S. Kasahara,
M. Shimoyama, Y. Kazama, M. Yamauchi, M. Holmström, Y. Futaana, R. Lundin, P. Wurz, M. Wieser,
H. Andersson, S. Karlsson, W. Benz, W.-H. Ip, L.-N. Hau, M. Hoshino, M. Fujimoto, K. Maezawa,
N. Terada, P. Trávni˘
cek, R. Smets, R. Modolo, F. Leblanc, R. Lallement, L. Zelenyi, H. Malova,
M.N. Nishino, Y.-C. Wang, M. Oka, M. Yagi, Y. Harada, L. Xie, J. Zhong, J. Vaverka, K. Keika,
W. Sun, L. Wang
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... The energy-time spectrogram of low-energy electrons obtained by one of the Mercury Electron Analyzers (MEA) (Saito et al., 2021) is shown in Figure 1a. We observe distinct changes in the electron energy spectra as indicated by the vertical gray lines corresponding to crossings of relevant boundaries. ...
... Figures 1b-1d show the energy-time spectrograms of low-energy ions obtained by the Mercury Ion Analyzer (MIA). During the third flyby of Mercury's magnetosphere, MIA operated in the solar wind mode, which uses multiple energy sweep tables (Saito et al., 2021). We utilize this data product to derive the ion energy spectra with 32 effective energy steps for each of the three energy ranges (low: ∼14-300 eV/q in Figure 1d, medium: ∼100-10 keV/q in Figure 1c, and high: ∼3-26 keV/q in Figure 1b) in time cadences of 4-16 s except for the data gaps shown in white. ...
... The negative spacecraft potential seems to be highly variable ( Figure 1d) possibly because of the varying electron temperature (Figure 1a, see also Rojo et al., 2024), which is the main driver of the negative charging. We take into account the estimated negative spacecraft potential as well as MIA's energy response (approximated by a Gaussian with a full width at half maximum of 12.7% (Saito et al., 2021)) in our fitting procedure as demonstrated in Figure 2b. For measurements in sunlight, we assume a zero spacecraft potential, which potentially results in an underestimation of the ion density if the actual spacecraft potential is positive. ...
Article
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Although solar wind‐driven convection is expected to dominate magnetospheric circulation at Mercury, its exact pattern remains poorly characterized by observations. Here we present BepiColombo Mio observations during the third Mercury flyby indicative of convection‐driven transport of low‐energy dense ions into the deep magnetosphere. During the flyby, Mio observed an energy‐dispersed ion population from the duskside magnetopause to the deep region of the midnight magnetosphere. A comparison of the observations with backward test particle simulations suggests that the observed energy dispersion structure can be explained in terms of energy‐selective transport by convection from the duskside tail magnetopause. We also discuss the properties and origins of more energetic ions observed in the more dipole‐like field regions of the magnetosphere in comparison to previously reported populations of the plasma sheet horn and ring current ions. Additionally, forward test particle simulations predict that most of the observed ions on the nightside will precipitate onto relatively low‐latitude regions of the nightside surface of Mercury for a typical convection case. The presented observations and simulation results reveal the critical role of magnetospheric convection in determining the structure of Mercury's magnetospheric plasma. The upstream driver dependence of magnetospheric convection and its effects on other magnetospheric processes and plasma‐surface interactions should be further investigated by in‐orbit BepiColombo observations.
... We use data obtained by the ion Mass Spectrum Analyzer(MSA) and Mercury Ion spectral Analyzer (MIA), the Mercury Electron Analyzers MEA1 and MEA2 belonging to the Mercury Plasma Particle Experiment (MPPE, Saito et al. (2021)) onboard the MMO (=Mio) spacecraft, and by the Planetary Ion Camera (PICAM) belonging to the Particle Instrument Suite for Determining the Sun-Mercury Interaction (SERENA, Orsini et al. (2021)) onboard the MPO spacecraft. Parameters of the different instruments are listed in Table 1. ...
... Ions remaining positive may create a stop signal on the start MCP but the respective products are not transmitted in cruise phase. The mass range is 1-60 amu with a mass resolution m/Δm = 10 for the "TSTL" product (Saito et al., 2021) available in cruise phase. This product represents an energy versus TOF matrix with resolution 64 energies × 1024 TOF channels at time resolution of 256 s. ...
... The MIA ion sensor (Saito et al., 2021) uses also a top-hat electrostatic analyzer with energy resolution varying from 2.2% to 12.7%. The field of view is adjustable from 6.4° × 270°-9.6° ...
Article
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Plain Language Summary The BepiColombo spacecraft is on its way through the inner solar system in a composite configuration consisting of two satellites and a propulsion unit with two large solar arrays. This configuration will only be separated after orbit insertion in December 2025. During the cruise phase and planetary flybys in the years 2021–2023 the ion spectrometers onboard the two satellites observed strong fluxes of low energy positive ions. We interpret these observations as being caused by outgassing of water from the spacecraft and a negative charging of the spacecraft caused by a high electron density surrounding the spacecraft. Around the first Mercury flyby in October 2021 all ion spectrometers observed two separate peaks in the low energy ion spectra. We explain these as being caused by water molecules being ionized by strong photon and electron fluxes in different regions of the negative potential surrounding the spacecraft. From these different potential regions ions are accelerated back to the spacecraft.
... The presence of such ions was confirmed during the third flyby of BepiColombo in June 2023. Ion analyzers that are parts of the MPPE (Mercury Plasma Particle Experiments) consortium onboard Mio (Saito et al., 2021) indeed recorded protons with energies well above 10 keV down to low altitudes, suggesting a closed ring current in the vicinity of the planet. In the present paper, we investigate a possible mechanism for the production of such energetic ion populations, namely, the effect of the electric field induced by rapid (a few seconds) magnetospheric reconfigurations. ...
Article
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We examine the dynamics of protons during tail‐like to dipole‐like reconfigurations of Mercury's magnetosphere. Such reconfigurations that frequently occur in the highly dynamical Hermean environment are accompanied by induced electric fields leading to short‐lived convection enhancements. Using test particle calculations, we show that, under the effect of such induced electric fields, protons may be subjected to prominent energization while being injected into the inner magnetosphere. We demonstrate that this energization occurs in a nonadiabatic manner and can reach several tens of keV, possibly leading to particle trapping around the planet. Recent observations from BepiColombo during Mercury's third flyby provide evidences of energetic protons drifting in the vicinity of the planet. The present impulsive energization process is a possible mechanism for the build‐up of such populations.
... During this flyby, the spacecraft reached low altitudes, traveling down to~235 km above the planet's surface. The ion plasma observations were recorded by the Mercury Ion Analyzer (MIA) and the Mass Spectrum Analyzer (MSA 16 ), and the electron observations by one of the Mercury Electron Analyzers (MEA 2) 15 . We describe the characteristics of the plasma and highlight the mass-per-charge information collected by MSA along the BepiColombo trajectory near Mercury. ...
Article
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Understanding Mercury’s magnetosphere is crucial for advancing our comprehension of how the solar wind interacts with the planetary magnetospheres. Despite previous missions, several gaps remain in our knowledge of Mercury’s plasma environment. Here, we present findings from BepiColombo’s third flyby, offering a synoptic view of the large scale structure and composition of Mercury’s magnetosphere. The Mass Spectrum Analyzer (MSA), Mass Ion Analyzer (MIA), and Mass Electron Analyzer (MEA) on the magnetospheric orbiter reveal insights, including the identification of trapped energetic hydrogen (H⁺) with energies around 20 keV e⁻¹ evidencing a ring current, and a cold ion plasma with energies below 50 eV e⁻¹. Additionally, we observe a Low-Latitude Boundary Layer (LLBL), which is a region of turbulent plasma at the edge of the magnetosphere, characterized by bursty ion enhancements, indicating an ongoing injection process in the duskside magnetosphere flank. These observations during cruise phase provide a tantalizing glimpse of future discoveries expected from the Mercury Plasma Particle Experiment (MPPE) instruments after orbit insertion, promising broader impacts on our understanding of planetary magnetospheres.
... The detection of extreme solar events, for example CMEs and solar flares, requires the detection of high-energy electrons and ions. Therefore, a high-energy particle instrument will be used with heritage from BepiColombo's high-energy particle instrument (HEP) [55]. The instrument has two sensors to detect both electrons and ions. ...
Article
Full-text available
Induced magnetospheres form around planetary bodies with atmospheres through the interaction of the solar wind with their ionosphere. Induced magnetospheres are highly dependent on the solar wind conditions and have only been studied with single spacecraft missions in the past. Without simultaneous measurements of solar wind variations and phenomena in the magnetosphere, establishing a link between both can only be done indirectly, using statistics over a large set of measurements. This gap in knowledge could be addressed by a multi-spacecraft plasma mission, optimized for studying global spatial and temporal variations in the magnetospheric system around Venus, which hosts the most prominent example of an induced magnetosphere in our solar system. The MVSE mission comprises four satellites, of which three are identical scientific spacecraft, carrying the same suite of instruments probing different regions of the induced magnetosphere and the solar wind simultaneously. The fourth spacecraft is the transfer vehicle which acts as a relay satellite for communications at Venus. In this way, changes in the solar wind conditions and extreme solar events can be observed, and their effects can be quantified as they propagate through the Venusian induced magnetosphere.Additionally, energy transfer in the Venusian induced magnetosphere can be investigated. The scientific payload includes instrumentation to measure the magnetic field, electric field, and ion–electron velocity distributions. This study presents the scientific motivation for the mission as well as requirements and the resulting mission design. Concretely, a mission timeline along with a complete spacecraft design, including mass, power, communication, propulsion and thermal budgets are given. This mission was initially conceived at the Alpbach Summer School 2022 and refined during a week-long study at ESA’s Concurrent Design Facility in Redu, Belgium.
... Here we report the first in situ observations made by BepiColombo's Mass Spectrum Analyzer (MSA) and Mercury Ion Analyzer (MIA) during the spacecraft's second Venus fly-by on 10 August 2021. The two sensors are part of the Mercury Plasma Particle Experiment (MPPE) 28,29 . Although MIA is a toroidal top-hat electrostatic energy analyser that measures ions without mass distinction, MSA combines a spherical top-hat electrostatic energy analyser with a polarized time-of-flight (TOF) chamber ('reflectron' type) to allow for ion measurements with enhanced mass resolution. ...
Article
Full-text available
On 10 August 2021, the Mercury-bound BepiColombo spacecraft performed its second fly-by of Venus and provided a short-lived observation of its induced magnetosphere. Here we report results recorded by the Mass Spectrum Analyzer on board Mio, which reveal the presence of cold O⁺ and C⁺ with an average total flux of ~4 ± 1 × 10⁴ cm⁻² s⁻¹ at a distance of about six planetary radii in a region that has never been explored before. The ratio of escaping C⁺ to O⁺ is at most 0.31 ± 0.2, implying that, in addition to atomic O⁺ ions, CO group ions or water group ions may be a source of the observed O⁺. Simultaneous magnetometer observations suggest that these planetary ions were in the magnetosheath flank in the vicinity of the magnetic pileup boundary downstream. These results have important implications regarding the evolution of Venus’s atmosphere and, in particular, the evolution of water on the surface of the planet.
... Since its development (Carlson et al. 1982;Young et al. 1988), the top-hat electrostatic analyzer (ESA) has become a standard instrument for recent space plasma observation missions such as Arase and BepiColombo/ Mio (e.g., Asamura et al. 2018;Yokota et al. 2017;Saito et al. 2021), because its axisymmetric shape provides uniform performance in all directions in principle, and high sensitivity with relatively small resources. If the spinning motion of the spacecraft is not used to acquire a field of view (FOV) in all directions, there is an option to extend the FOV with deflectors at the entrance of the analyzer (e.g., Pollock et al. 2016;Yokota et al. 2005;Yokota et al. 2021;Kasahara et al. 2023). ...
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We have developed a low-energy particle experiment that alternately measures ions and electrons in space. The ability to switch between ion and electron measurements is achieved by simply adding ultra-thin carbon foils and positive and negative outputs to a conventional top-hat electrostatic analyzer and a high-voltage power supply, respectively. The advantage of this experiment is that it can perform both ion and electron measurements using only one MCP-based detector for electrons, since it detects secondary electrons emitted from the carbon foils. For the SS520-3 sounding rocket program, we prepared two identical energy analyzers, one for ions and the other for electrons to demonstrate this technique. Laboratory tests confirmed that the performance of the two analyzers was comparable to that of conventional analyzers for ion and electrons. The SS520-3 rocket experiment in the high latitude auroral region yielded observations that captured typical features of ions and electrons, which were similar to previous observations. Graphical Abstract
... The origin of these electron burst events and understanding the similarity and the difference in the behavior of electron dynamics between Mercury's and Earth's magnetospheres may elucidate particle acceleration mechanisms underlying in our Solar Systems. The BepiColombo Mio spacecraft will begin comprehensive plasma and wave observations of Mercury's magnetosphere in orbit from 2025 Saito et al., 2021;Yagitani et al., 2020). Before BepiColombo performs in-situ comprehensive observations at Mercury (Milillo et al., 2020), in this study we estimate possible generation regions of chorus waves in Mercury's magnetosphere to discuss the possible evolution of Mercury's radiation and/or ring electron current belt through wave-particle interactions. ...
Article
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Chorus waves are a kind of intense electromagnetic emission wave in magnetized planets and can play important roles in the kinetic electron dynamics in planetary magnetospheres. Rapid changes of the ring electron current belt in Mercury’s magnetosphere and the contribution of chorus waves have remained long‐standing scientific issues from the first Mercury flyby observations by Mariner 10 in 1970s because of the small size of the magnetosphere. Based on theoretical analyses and simulations successfully reconstructing Earth’s chorus wave properties, we report on possible generation regions of chorus waves in Mercury’s magnetosphere. The theoretical analysis for low‐temperature‐anisotropy electrons shows a clear asymmetric day–night spatial distribution of the possible chorus generation region because of the difference in the nonlinear convective wave growth along the magnetic field lines. Simulation results show a rapid enhancement of the ring electron current belt by resonant interactions with repetitive chorus waves. Our study suggests that energetic electrons in Mercury’s magnetosphere can be enhanced locally by nonlinear chorus wave–particle interactions.
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Mercury's small magnetosphere is embedded in the dynamic and intense solar wind environment characteristic of the inner heliosphere. Both the magnitude and orientation of the interplanetary magnetic field (IMF) significantly influence the solar wind‐magnetospheric interaction at Mercury, driving phenomena such as magnetic reconnection. The MErcury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft provided in‐situ magnetic field measurements of the solar wind, the magnetosheath, and the magnetosphere along each orbit. However, it is a challenge to directly assess the IMF's impact on Mercury's plasma environment due to the temporal separation between observations within the solar wind and the magnetosphere, especially in the absence of an upstream monitor. Here, we present a feedforward neural network (FNN) trained on a subset of magnetosheath observations to estimate the strength and orientation of the IMF upstream of the bow shock. Utilizing magnetosheath magnetic field, cylindrical spatial coordinates, and heliocentric distance measurements, the FNN predicts upstream IMF conditions with an score of 0.70 and mean averaged error of 5.3 nT, thereby greatly decreasing the temporal separation between IMF estimates and magnetospheric measurements throughout the MESSENGER mission. This approach yields IMF estimates for all magnetosheath data measured by MESSENGER, providing a useful tool for future investigations of the IMF impact on Mercury's magnetosphere. This method will be integrable with the dual‐spacecraft BepiColombo magnetosheath measurements, providing useful estimates of upstream IMF conditions particularly during the extended periods in which neither spacecraft sample the solar wind. Our results demonstrate the utility of machine learning techniques on advancing space science research.
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Context . The Mercury electron analyzer (MEA) obtained new electron observations during the first three Mercury flybys by BepiColombo on October 1, 2021 (MFB1), June 23 , 2022 (MFB2), and June 19, 2023 (MFB3). BepiColombo entered the dusk side magnetotail from the flank magnetosheath in the northern hemisphere, crossed the Mercury solar orbital equator around midnight in the magnetotail, traveled from midnight to dawn in the southern hemisphere near the closest approach, and exited from the post-dawn magnetosphere into the dayside magnetosheath. Aims . We aim to identify the magnetospheric boundaries and describe the structure and dynamics of the electron populations observed in the various regions explored along the flyby trajectories. Methods . We derive 4s time resolution electron densities and temperatures from MEA observations. We compare and contrast our new BepiColombo electron observations with those obtained from the Mariner 10 scanning electron spectrometer (SES) 49 yr ago. Results . A comparison to the averaged magnetospheric boundary crossings of MESSENGER indicates that the magnetosphere of Mercury was compressed during MFB1, close to its average state during MFB2, and highly compressed during MFB3. Our new MEA observations reveal the presence of a wake effect very close behind Mercury when BepiColombo entered the shadow region, a significant dusk-dawn asymmetry in electron fluxes in the nightside magnetosphere, and strongly fluctuating electrons with energies above 100s eV in the dawnside magnetosphere. Magnetospheric electron densities and temperatures are in the range of 10–30 cm ⁻³ and above a few 100s eV in the pre-midnight-sector, and in the range of 1–100 cm ⁻³ and well below 100 eV in the post-midnight sector, respectively. Conclusions . The MEA electron observations of different solar wind properties encountered during the first three Mercury flybys reveal the highly dynamic response and variability of the solar wind-magnetosphere interactions at Mercury. A good match is found between the electron plasma parameters derived by MEA in the various regions of the Hermean environment and similar ones derived in a few cases from other instruments on board BepiColombo.
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Energetic particle bursts associated with dipolarization events within Mercury's magnetosphere were first observed by Mariner 10. The events appear analogous to particle injections accompanying dipolarization events at Earth. The Energetic Particle Spectrometer (3 s resolution) aboard MESSENGER determined the particle bursts are composed entirely of electrons with energies ≤ ~300 keV. Here we use the Gamma-Ray Spectrometer high-time-resolution (10 ms) energetic electron measurements to examine the relationship between energetic electron injections and magnetic field dipolarization in Mercury's magnetotail. Between March 2013 and April 2015, we identified 2976 electron burst events within Mercury's magnetotail, 538 of which are closely associated with dipolarization events. These dipolarizations were detected on the basis of their rapid (~2 s) increase in the northward component of the tail magnetic field (ΔBz ~ 30 nT), which typically persists for ~10 s. Similar to at Earth, we find these dipolarizations appear to be low-entropy, depleted flux tubes convecting planetward following the collapse of the inner magnetotail. We find electrons experience brief, yet intense, betatron and Fermi acceleration during these dipolarizations, reaching energies ~130 keV and contributing to nightside precipitation. Thermal protons experience only modest betatron acceleration. While only ~25% of energetic electron events in Mercury's magnetotail were directly associated with dipolarization, the remaining events are consistent with the Near-Mercury Neutral Line model of magnetotail injection and eastward drift about Mercury, finding that electrons may participate in Shabansky-like closed drifts about the planet. Magnetotail dipolarization may be the dominant source of energetic electron acceleration in Mercury's magnetosphere.