Remote energetic neutral atom imaging of electric potential over a lunar magnetic anomaly

Futaana, Yoshifumi; Barabash, S.; Wieser, Martin; Lue, Charles; Würz, Peter; Vorburger, Audrey; Bhardwaj, Anil; Asamura, Kazushi

doi:10.1002/grl.50135

Cited by 60 publications

(75 citation statements)

References 40 publications

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“…For a full understanding of the structure and dynamics of magnetosphere, however, a six-dimensional Vlasov simulation (with three spatial dimensions) is essential, because the topology of magnetic fields and convection pattern is modified in three spatial dimensions from those in two spatial dimensions. As the in situ observation shows, there is no bow shock above the Lunar magnetic anomaly (Futaana et al 2013), while the formation of the bow shock is confirmed in the present global simulation with two spatial dimensions. The full six-dimensional global Vlasov simulation is left as a far future study, since it would require massive computing resources beyond Exascale.…”

Section: Resultssupporting

confidence: 79%

A high-resolution global Vlasov simulation of a small dielectric body with a weak intrinsic magnetic field on the K computer

Umeda

Fukazawa

2015

Earth Planet Sp

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The interaction between the solar wind and solar system bodies, such as planets, satellites, and asteroids, is one of the fundamental global-scale phenomena in space plasma physics. In the present study, the electromagnetic environment around a small dielectric body with a weak intrinsic magnetic field is studied by means of a first-principle kinetic plasma simulation, which is a challenging task in space plasma physics as well as high-performance computing. Due to several computational limitations, five-dimensional full electromagnetic Vlasov simulations with two configuration space and three velocity space coordinates are performed with two different spatial resolutions. The Debye-scale charge separation is not solved correctly in the simulation run with a low spatial resolution, while all the physical processes in collisionless plasma are included in the simulation run with a high spatial resolution. The direction comparison of electromagnetic fields between the two runs shows that there is small difference in the structure of magnetic field lines. On the other hand, small-scale fine structures of electrostatic fields are enhanced by the electric charge separation and the charge accumulation on the surface of the body in the high-resolution run, while these structures are absent in the low-resolution runs. These results are consistent with the conventional understanding of plasma physics that the structure and dynamics of global magnetic fields, which are generally described by the magneto-hydro-dynamics (MHD) equations, are not affected by electron-scale microphysics.

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Section: Resultssupporting

confidence: 79%

A high-resolution global Vlasov simulation of a small dielectric body with a weak intrinsic magnetic field on the K computer

Umeda

Fukazawa

2015

Earth Planet Sp

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“…A complicated magnetic footprint that is limited in extent and isolated was observed by the SARA instument on Chandrayaan-1 Vorburger et al 2012;Futaana et al 2013) (at  22 S and  240 E on the lunar far side, and shown in the left two panels of Figure 6). Such a structure would appear in the far-field as a single dipole, similar to that used in the simulation (shown in the right panels of Figure 6).…”

Section: Comparison With Lunar Swirlsmentioning

confidence: 94%

3d Pic Simulations of Collisionless Shocks at Lunar Magnetic Anomalies and Their Role in Forming Lunar Swirls

Bamford

Alves

Cruz

et al. 2016

ApJ

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Investigation of the lunar crustal magnetic anomalies offers a comprehensive long-term data set of observations of small-scale magnetic fields and their interaction with the solar wind. In this paper a review of the observations of lunar mini-magnetospheres is compared quantifiably with theoretical kinetic-scale plasma physics and 3D particlein-cell simulations. The aim of this paper is to provide a complete picture of all the aspects of the phenomena and to show how the observations from all the different and international missions interrelate. The analysis shows that the simulations are consistent with the formation of miniature (smaller than the ion Larmor orbit) collisionless shocks and miniature magnetospheric cavities, which has not been demonstrated previously. The simulations reproduce the finesse and form of the differential proton patterns that are believed to be responsible for the creation of both the "lunar swirls" and "dark lanes." Using a mature plasma physics code like OSIRIS allows us, for the first time, to make a side-by-side comparison between model and space observations. This is shown for all of the key plasma parameters observed to date by spacecraft, including the spectral imaging data of the lunar swirls. The analysis of miniature magnetic structures offers insight into multi-scale mechanisms and kinetic-scale aspects of planetary magnetospheres.

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“…Energetic neutral atom (ENA) imaging of the Moon from Chandrayaan‐1 observations showed that a partial void of the solar wind plasma, a minimagnetosphere, forms above one of the strongest lunar magnetic anomalies located at the Crisium antipode near the Gerasimovich crater, known as Gerasimovich magnetic anomaly [ Wieser et al , ; Vorburger et al , ; Futaana et al , ]. They showed that the ENA flux was substantially reduced above the magnetic anomalies, while it was increased in the surrounding regions, indicating plasma deflection around crustal fields.…”

Section: Introductionmentioning

confidence: 99%

“…They showed that the ENA flux was substantially reduced above the magnetic anomalies, while it was increased in the surrounding regions, indicating plasma deflection around crustal fields. By studying the energy spectrum of the ENA population, they estimated an electrostatic potential of larger than +135 V inside the Gerasimovich magnetic anomaly [ Futaana et al , ]. They also found that the Gerasimovich magnetic anomaly possesses a clearer correlation between the incident plasma parameters and the surface shielding efficiency compared to the other crustal fields, which is presumably due to its simple magnetic field topology compared to the other crustal fields, especially compared to the South Pole‐Aitken basin region [ Vorburger et al , ].…”

Section: Introductionmentioning

confidence: 99%

“…Here we use a three‐dimensional self‐consistent hybrid plasma model [ Holmström , ; Holmström et al , 2012] and include the empirical model of lunar crustal magnetization developed by Purucker and Nicholas [] into our model to study the solar wind interaction with a localized lunar crustal field. Since the interaction with Gerasimovich magnetic anomaly has been more extensively studied compared to the other crustal fields [ Wieser et al , ; Vorburger et al , ; Futaana et al , ], and due to its relatively simple magnetic field structure, we focus on the solar wind interaction with the Gerasimovich magnetic anomaly. We examine the effects of low and high solar wind dynamic pressures on this interaction and study the surface shielding efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Solar wind plasma interaction with Gerasimovich lunar magnetic anomaly

et al. 2015

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We present the results of the first local hybrid simulations (particle ions and fluid electrons) for the solar wind plasma interaction with realistic lunar crustal fields. We use a three‐dimensional hybrid model of plasma and an empirical model of the Gerasimovich magnetic anomaly based on Lunar Prospector observations. We examine the effects of low and high solar wind dynamic pressures on this interaction when the Gerasimovich magnetic anomaly is located at nearly 20∘ solar zenith angle. We find that for low solar wind dynamic pressure, the crustal fields mostly deflect the solar wind plasma, form a plasma void at very close distances to the Moon (below 20 km above the surface), and reflect nearly 5% of the solar wind in charged form. In contrast, during high solar wind dynamic pressure, the crustal fields are more compressed, the solar wind is less deflected, and the lunar surface is less shielded from impinging solar wind flux, but the solar wind ion reflection is more locally intensified (up to 25%) compared to low dynamic pressures. The difference is associated with an electrostatic potential that forms over the Gerasimovich magnetic anomaly as well as the effects of solar wind plasma on the crustal fields during low and high dynamic pressures. Finally, we show that an antimoonward Hall electric field is the dominant electric field for ∼3 km altitude and higher, and an ambipolar electric field has a noticeable contribution to the electric field at close distances (<3 km) to the Moon.

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Remote energetic neutral atom imaging of electric potential over a lunar magnetic anomaly

Cited by 60 publications

References 40 publications

A high-resolution global Vlasov simulation of a small dielectric body with a weak intrinsic magnetic field on the K computer

A high-resolution global Vlasov simulation of a small dielectric body with a weak intrinsic magnetic field on the K computer

3d Pic Simulations of Collisionless Shocks at Lunar Magnetic Anomalies and Their Role in Forming Lunar Swirls

Solar wind plasma interaction with Gerasimovich lunar magnetic anomaly

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