Three‐dimensional full‐kinetic simulation of the solar wind interaction with a vertical dipolar lunar magnetic anomaly

Deca, Jan; Divin, Andrey; Wang, Xu; Lembège, Bertrand; Horányi, M.; Lapenta, Giovanni

doi:10.1002/2016gl068535

Cited by 8 publications

(7 citation statements)

References 39 publications

(59 reference statements)

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“…Following from several magnetometer‐based studies of magnetic field structure (Hemingway & Garrick‐Bethell, ; Shibuya et al, ; Tsunakawa et al, ), together with a series of hybrid and kinetic plasma simulations (e.g., Bamford et al, , ; Deca et al, ; Poppe et al, , ; Zimmerman et al, ), we use lunar swirl morphology as a proxy for the structure of near‐surface magnetic fields. This allows us to place strong constraints on the geometry of the underlying magnetic source bodies.…”

Section: Discussionmentioning

confidence: 99%

“…Roughly speaking, portions of the surface with open magnetic field lines may be expected to experience normal or even accelerated solar wind‐related space weathering, leading to darkening, whereas portions of the surface beneath closed magnetic field lines should experience greater protection from solar wind weathering, thus remaining relatively bright (Hemingway & Garrick‐Bethell, ). Indeed, magnetometer‐based studies of magnetic field structure (Hemingway & Garrick‐Bethell, ; Shibuya et al, ; Tsunakawa et al, ), as well as hybrid and kinetic plasma simulations (e.g., Bamford et al, , ; Deca et al, , ; Fatemi et al, ; Giacalone & Hood, ; Jarvinen et al, ; Poppe et al, , ; Zimmerman et al, ), indicate that swirl morphology may be dictated by magnetic field topology in precisely this way. It has also been proposed that swirls may be the result of electrostatic (Garrick‐Bethell et al, ) or magnetic (Pieters et al, ) sorting of fine‐grained materials, rather than of deflection of solar wind.…”

Section: Introductionmentioning

confidence: 99%

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Lunar Swirl Morphology Constrains the Geometry, Magnetization, and Origins of Lunar Magnetic Anomalies

Hemingway

Tikoo

2018

JGR Planets

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Lunar swirls are collections of finely structured bright and dark surface markings, alternating over length scales of typically 1-5 km. If swirls are the result of plasma interactions with crustal magnetic anomalies or electrostatic or magnetic sorting of fine materials, the magnetic field orientation must vary over similar length scales. This requires that the associated source bodies be both shallow and narrow in horizontal extent. The correspondingly restricted volume of the source bodies in turn implies strong rock magnetization. Here we show that if ∼300-nT surface fields are necessary to produce observable swirl markings, the required rock magnetization must be > 0.5 A/m, even for very shallow sources and likely closer to ∼ 2 A/m or more. This strong source rock magnetization, together with the geometric constraints that favor magmatic structures such as dikes or lava tubes, requires a mechanism to enhance the magnetic carrying capacity of the rocks. We propose that heating associated with magmatic activity could thermochemically alter host rocks and impart them with magnetizations an order of magnitude stronger than is typical of lunar mare basalts. Our results both place constraints on the geometry and magnetization of the source bodies and provide clues about the possible origins of the Moon's crustal magnetic anomalies. Plain Language SummaryLunar swirls are collections of finely structured, bright and dark surface markings, alternating over length scales of typically 1-5 km. Swirls are thought to form where local magnetic fields shield parts of the lunar surface from exposure to the solar wind or where those magnetic fields lead to sorting of some of the finest lunar soils. In either case, the length scales of swirls are effectively telling us about the structure of near-surface magnetic fields on scales that are finer than what can be measured from lunar orbit. Here we use this length scale information, along with estimates of the strength of those magnetic fields, to obtain new constraints on the underlying magnetized rocks, showing that they must be shallow, narrow, and strongly magnetized. This result helps us to better understand the origin of these magnetized rocks and the history of lunar magnetism more generally. In particular, we suggest that these rocks were likely injected into the crust in the form of dikes or subsurface channels of flowing lava and that they cooled slowly, leading to enhancement of their metal content and enabling the rocks to capture a stable record of the Moon's ancient global magnetic field. Key Points:• Lunar swirl morphology suggests finely structured near-surface magnetic fields, requiring narrow, shallow magnetic source bodies • The source bodies underlying swirls must be much more strongly magnetized than is typical of lunar mare basalts • The inferred source geometry and magnetization could be explained both by magmatic intrusions and associated thermochemical alteration

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lunar Swirl Morphology Constrains the Geometry, Magnetization, and Origins of Lunar Magnetic Anomalies

Hemingway

Tikoo

2018

JGR Planets

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“…In addition, some current peaks may be associated with local magnetic anomalies. Lunar magnetic anomalies are thought to be able to prevent the incoming solar wind and reduce the solar wind flux on the lunar surface (Deca et al, 2016; Xie et al, 2015). As a result, they can change the flux of backscattered solar wind and lead to a disturbance in the LDEX current, as discussed by (Walker et al, 2017).…”

Section: Dust Fountain Observed By Ladeementioning

confidence: 99%

Lunar Dust Fountain Observed Near Twilight Craters

Xie

Zhang

et al. 2020

Geophysical Research Letters

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Lunar horizon glows observed by the Apollo missions suggested a dense dust exosphere near the lunar terminator. But later missions failed to see such a high-density dust exosphere. Why the Apollo missions could observe so large number of dust grains remains a mystery. For the first time, we report five dust enhancement events observed by the Lunar Dust Experiment on board Lunar Atmosphere and Dust Environment Explorer mission, which happen near a twilight crater with dust densities comparable to the Apollo measurements. Moreover, the dust densities are larger on the downstream side of the crater and favor a higher solar wind temperature, consistent with an electrostatic dust lofting from the negatively charged crater floor. We also check the Apollo observations and find similar twilight craters, suggesting that the so-called dust exosphere is not a global phenomenon but just a local electrified dust fountain near twilight craters. Plain Language Summary With in situ dust measurements, we find that a shadowed crater near the terminator can dramatically change the surface electrical environment and bring a dense dust cloud surrounding the crater, which should be carefully assessed by engineers for future lunar explorations. Moreover, our findings have the general implications in studying the dust environment near large topographic features (mountains and deep craters) of all kinds of airless bodies. On the other hand, the electrostatic mechanism has been improved in recent years. Stubbs et al. (2006) proposed a dynamic fountain model, in which the like-charged dust grains with radii of 0.01-0.1 μm could be RESEARCH LETTER

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“…Summarizing broadly, these simulations show that field-aligned potentials in martian crustal cusp regions can be self-consistently and stably formed and in turn, that these field-aligned potentials stimulate ionospheric ion outflow in excess of that which occurs in unmagnetized regions due to polar-wind type ambipolar expansion (e.g., Ergun et al, 2016;Xu et al, 2018). The formation of the additional field-aligned potentials arises from differential penetration of magnetospheric ions and electrons into cusps regions, in analogy with similar processes that occur in Earth's polar region (e.g., Schriver, 1999) and in lunar crustal magnetic field cusps (e.g., Deca et al, 2016;Poppe et al, 2012;Saito et al, 2010). Due to the presence of additional electrostatic field-aligned potentials, the model in turn predicts increased ionospheric ion outflow, with the total escaping ion flux correlated with the strength of the crustal magnetic field.…”

Section: Discussionmentioning

confidence: 98%

Particle‐In‐Cell Modeling of Martian Magnetic Cusps and Their Role in Enhancing Nightside Ionospheric Ion Escape

Poppe

Brain

Dong

et al. 2021

Geophysical Research Letters

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Over its ∼4.5 billion years history, Mars has lost its atmosphere. While there exists a preponderance of evidence that the early martian climate was warm and wet, with relatively high global atmospheric pressures (e.g., Davis et al., 2016; Owen, 1992; Poulet et al., 2005), Mars today is cold and dry, with a thin global CO 2 atmosphere of <∼10 mbar of pressure (Hess et al., 1979). Thus, an enduring scientific question remains: namely, how, why, and when did Mars lose its atmosphere? Sequestration of atmospheric carbon into the surface and subsurface of Mars is one postulated pathway, yet evidence suggests that there is an insufficient amount of carbon in the present-day surface of Mars to account for the expected atmospheric loss (e.g., Bibring et al., 2005; Edwards & Ehlmann, 2015). Atmospheric escape to space is the other main loss pathway and manifests itself in a variety of processes, including Jeans escape (e.g.,

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Three‐dimensional full‐kinetic simulation of the solar wind interaction with a vertical dipolar lunar magnetic anomaly

Cited by 8 publications

References 39 publications

Lunar Swirl Morphology Constrains the Geometry, Magnetization, and Origins of Lunar Magnetic Anomalies

Lunar Swirl Morphology Constrains the Geometry, Magnetization, and Origins of Lunar Magnetic Anomalies

Lunar Dust Fountain Observed Near Twilight Craters

Particle‐In‐Cell Modeling of Martian Magnetic Cusps and Their Role in Enhancing Nightside Ionospheric Ion Escape

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