Stellar winds and planetary bodies simulations: Lunar type interaction in super-Alfvénic and sub-Alfvénic flows

Vernisse, Y.; Kriegel, H.; Wiehle, Stefan; Motschmann, U.; Glaßmeier, Karl‐Heinz

doi:10.1016/j.pss.2013.04.004

Cited by 22 publications

(35 citation statements)

References 46 publications

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“…Fatemi et al [] assumed a resistive Moon, and they did not detect any signature of magnetic field and plasma compressions outside the Mach cone. Though Vernisse et al [] showed magnetic field enhancement in the lunar dayside which was due to the lunar conductivity in their simulations. However, our simulations here show that the magnetic field perturbations outside the Mach cone result in forming an additional current system to those described previously.…”

Section: Discussionmentioning

confidence: 88%

“…Recently, Fatemi et al [2013] and Vernisse et al [2013] using hybrid simulations explained the current system in the lunar Mach cone. They assumed the Moon as a plasma absorber without any proton reflection.…”

Section: 1002/2014ja019900mentioning

confidence: 99%

“…Thus, the supersonic flow of the solar wind plasma is mostly absorbed on the lunar dayside, leaving a plasma wake downstream with a plasma cavity on the nightside [Lyon et al, 1967]. While the interplanetary magnetic field (IMF) convects through the nonconductive body of the Moon relatively undisturbed [Colburn et al, 1971;Halekas et al, 2005], the current system forming in the lunar wake enhances the magnetic fields in the wake cavity and depresses them in the surrounding expansion region [Colburn et al, 1967;Fatemi et al, 2013;Vernisse et al, 2013]. These perturbations of the magnetic field and plasma in the lunar wake are confined to a region bounded by a magnetosonic Mach cone [Whang and Ness, 1970;Holmström et al, 2012].…”

Section: Introductionmentioning

confidence: 99%

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Effects of protons reflected by lunar crustal magnetic fields on the global lunar plasma environment

et al. 2014

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Solar wind plasma interaction with lunar crustal magnetic fields is different than that of magnetized bodies like the Earth. Lunar crustal fields are, for typical solar wind conditions, not strong enough to form a (bow)shock upstream but rather deflect and perturb plasma and fields. Here we study the global effects of protons reflected from lunar crustal magnetic fields on the lunar plasma environment when the Moon is in the unperturbed solar wind. We employ a three‐dimensional hybrid model of plasma and an observed map of reflected protons from lunar magnetic anomalies over the lunar farside. We observe that magnetic fields and plasma upstream over the lunar crustal fields compress to nearly 120% and 160% of the solar wind, respectively. We find that these disturbances convect downstream in the vicinity of the lunar wake, while their relative magnitudes decrease. In addition, solar wind protons are disturbed and heated at compression regions and their velocity distribution changes from Maxwellian to a non‐Maxwellian. Finally, we show that these features persists, independent of the details of the ion reflection by the magnetic fields.

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Section: Discussionmentioning

confidence: 88%

Section: 1002/2014ja019900mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of protons reflected by lunar crustal magnetic fields on the global lunar plasma environment

et al. 2014

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“…Such field magnitude variations in the wake are imposed by pressure gradient forces [e.g., Khurana et al, 2008]. Using theoretical analyses and simulations, Vernisse et al [2013] systematically studied the interaction between stellar winds, whether super-Alfvénic or sub-Alfvénic, and highly resistive planetary bodies. They argued that diamagnetic currents, which arise from pressure gradients, are significant sources of magnetic perturbations in a lunar-type interaction.…”

Section: Introductionmentioning

confidence: 99%

Alfvén wings in the lunar wake: The role of pressure gradients

et al. 2016

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Strongly conducting or magnetized obstacles in a flowing plasma generate structures called Alfvén wings, which mediate momentum transfer between the obstacle and the plasma. Nonconducting obstacles such as airless planetary bodies can generate such structures, which, however, have so far been seen only in sub‐Alfvénic regime. A novel statistical analysis of simultaneous measurements made by two ARTEMIS satellites, one in the solar wind upstream of the Moon and one in the downstream wake, and comparison of the data with results of a three‐dimensional hybrid model of the interaction reveal that the perturbed plasma downstream of the Moon generates Alfvén wings in super‐Alfvénic solar wind. In the wake region, magnetic field lines bulge toward the Moon and the plasma flows are significantly perturbed. We use the simulation to show that some of the observed bends of the field result from field‐aligned currents. The perturbations in the wake thus arise from a combination of compressional and Alfvénic perturbations. Because of the super‐Alfvénic background flow of the solar wind, the two Alfvén wings fold back to form a small intersection angle. The currents that form the Alfvén wing in the wake are driven by both plasma flow deceleration and a gradient of plasma pressure, positive down the wake from the region just downstream of the Moon. Such Alfvén wing structures, caused by pressure gradients in the wake and the resulting plasma slowdown, should exist downstream of any nonconducting body in a super‐Alfvénic plasma flow.

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“…The implicit assumption is that the smoothed surface is sufficiently sharp to accurately render the physics of the plasma interaction. Realistically, the smoothing imposes a possible limitation on the DHM's applicability [ Vernisse et al ., , p. 39], since insufficient internal resistance allows too much current to permeate the body, while excessive ρ 0 may inhibit exterior currents by requiring too much surface smoothing. The Δ t and Δ x used (which are limited by computing speed) may in some cases not allow for any physically realistic combination of ρ 0 and a to be simulated.…”

Section: Differential Hybrid Models: the Sharp Surface Problemmentioning

confidence: 99%

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea

et al. 2014

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Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere.Key PointsSurface current balance condition yields a current system at astronomical bodiesCurrent system possible for sharp (airless) objects of any sizeCurrent system is thermoelectric and motion through the plasma nonessential

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Stellar winds and planetary bodies simulations: Lunar type interaction in super-Alfvénic and sub-Alfvénic flows

Cited by 22 publications

References 46 publications

Effects of protons reflected by lunar crustal magnetic fields on the global lunar plasma environment

Effects of protons reflected by lunar crustal magnetic fields on the global lunar plasma environment

Alfvén wings in the lunar wake: The role of pressure gradients

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea

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