First remote measurements of lunar surface charging from ARTEMIS: Evidence for nonmonotonic sheath potentials above the dayside surface

Halekas, J. S.; Delory, G. T.; Farrell, W. M.; Angelopoulos, V.; McFadden, J. P.; Bonnell, J. W.; Fillingim, M. O.; Plaschke, Ferdinand

doi:10.1029/2011ja016542

Cited by 27 publications

(24 citation statements)

References 24 publications

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“…The broadband electrostatic modes observed here resemble those observed in the terrestrial magnetosphere [ Halekas et al , ]. The free energy source for the broadband electrostatic waves observed above the dayside lunar surface in the terrestrial magnetosphere was attributed to upward electron beams accelerated through a nonmonotonic surface potential layer [ Halekas et al , , ; Poppe et al , , ]. As we have seen in Figures d and l, we have the upward electron beams reflected and accelerated by a moving obstacle.…”

Section: Case Studysupporting

confidence: 79%

Extended lunar precursor regions: Electron‐wave interaction

et al. 2014

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We present Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) observations of electron‐wave interactions which extend to quite large distances upstream from the Moon. We first study electron velocity distributions and wave spectra on an event basis. In both the solar wind and terrestrial plasma sheet, we observe strong whistler wave activity on the magnetic field lines connected to the dayside lunar surface. These whistlers are most likely driven by the anisotropy of upward electrons caused by surface absorption. The whistler growth rates computed from the measured electron distributions successfully reproduced the spectral characteristics of the observed ∼100 Hz narrowband oscillations and those reaching lower frequencies. Meanwhile, the incoming solar wind strahl beam is occasionally isotropized near the Moon, and broadband electrostatic waves are observed simultaneously, suggesting streaming instabilities between the incoming and outgoing beams. Based on the case study, we statistically survey the spatial variations of the characteristic quantities of the upstream electron‐wave interactions. Both the electron anisotropy and electromagnetic wave intensity decay with increasing field line distances but remain higher than the ambient level at 6 lunar radii (∼10,000 km) or more. The strahl electron isotropization and electrostatic waves are found mainly at lower altitudes below 1 lunar radius. The electron anisotropy and whistler intensity exhibit clear anticorrelation with crustal magnetic fields, indicating that the magnetic anomalies suppress the whistler wave growth. The ARTEMIS observations convincingly illustrate that the lunar influence on electrons reaches out to 6 lunar radii or more upstream from the Moon.

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Section: Case Studysupporting

confidence: 79%

Extended lunar precursor regions: Electron‐wave interaction

et al. 2014

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“…We interpret the Apollo SIDE TID stair-step flux profiles as further evidence of the presence of nonmonotonic potentials above the lunar surface while in the terrestrial magnetotail, in concurrence with previous orbital measurements [e.g., Halekas et al, 2008Halekas et al, , 2011Halekas et al, , 2012Poppe et al, 2011Poppe et al, , 2012. Thus, the identification of this stair-step spectral form using instrumentation on the lunar surface is another of many techniques that allow us to measure lunar surface potential with an ion instrument on the lunar surface in various plasma environments [e.g., Freeman and Ibrahim, 1975;Freeman et al, 1972Freeman et al, , 1973Goldstein, 1974;Lindeman et al, 1973;Benson, 1977;Manka and Michel, 1973].…”

Section: Discussionsupporting

confidence: 91%

Stair‐step particle flux spectra on the lunar surface: Evidence for nonmonotonic potentials?

Collier

Newheart

Poppe

et al. 2017

Geophysical Research Letters

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We present examples of unusual “stair‐step” differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e., potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface‐based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote‐sensing orbiter observations on the Moon's exospheric and electrostatic properties.

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“…The beam consists of secondary and/or photoelectrons produced at the surface, and accelerated through a non‐monotonic surface potential layer, as observed previously by both Lunar Prospector [ Halekas et al , 2005, 2008b; Poppe et al , 2011] and ARTEMIS [ Halekas et al , 2011a]. Poppe et al [2012] have presented detailed model‐data comparisons for this date, so we will not discuss the electron beam in detail, other than to mention that it may ultimately exist in order to help maintain quasi‐neutrality on flux tubes upstream from the Moon [ Halekas et al , 2011a, 2012]. We note that the beam has high enough flux and a sharp enough peak to produce a positive slope even in the reduced distribution (Figure 8, bottom right), indicating that electrostatic beam modes have not yet produced a plateau in the distribution.…”

Section: Lunar Precursor Observations In the Terrestrial Magnetospherementioning

confidence: 94%

“…The loss cone distribution must result from reflection from crustal magnetic fields near the surface. The beam consists of secondary and/or photoelectrons produced at the surface, and accelerated through a non-monotonic surface potential layer, as observed previously by both Lunar Prospector [Halekas et al, 2005[Halekas et al, , 2008bPoppe et al, 2011] and ARTEMIS [Halekas et al, 2011a]. Poppe et al [2012] have presented detailed model-data comparisons for this date, so we will not discuss the electron beam in detail, other than to mention that it may ultimately exist in order to help maintain quasi-neutrality on flux tubes upstream from the Moon [Halekas et al, 2011a.…”

Section: Reflected and Accelerated Electronsmentioning

confidence: 99%

Lunar precursor effects in the solar wind and terrestrial magnetosphere

et al. 2012

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[1] The two ARTEMIS probes observe significant precursor activity upstream from the Moon, when magnetically connected to the dayside lunar surface. The most common signature consists of high levels of whistler wave activity near half of the electron cyclotron frequency. This precursor activity extends to distances of many thousands of km, in both the solar wind and terrestrial magnetosphere. In the magnetosphere, electrons reflect from a combination of magnetic and electrostatic fields above the lunar surface, forming loss cone distributions. In the solar wind they generally form conics, as a result of reflection from an obstacle moving with respect to the plasma frame (just as at a shock). The anisotropy associated with these reflected electrons provides the free energy source for the whistlers, with cyclotron resonance conditions met between the reflected source population and Moonward-propagating waves. These waves can in turn affect incoming plasma, and we observe significant perpendicular electron heating and plasma density depletions in some cases. In the magnetosphere, we also observe broadband electrostatic modes driven by beams of secondary electrons and/or photoelectrons accelerated outward from the surface. We also occasionally see waves near the ion cyclotron frequency in the magnetosphere. These lower frequency waves, which may result from the presence of ions of lunar origin, modulate the whistlers described above, as well as the electrons. Taken together, our observations suggest that the presence of the Moon leads to the formation of an upstream region analogous in many ways to the terrestrial electron foreshock.

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First remote measurements of lunar surface charging from ARTEMIS: Evidence for nonmonotonic sheath potentials above the dayside surface

Cited by 27 publications

References 24 publications

Extended lunar precursor regions: Electron‐wave interaction

Extended lunar precursor regions: Electron‐wave interaction

Stair‐step particle flux spectra on the lunar surface: Evidence for nonmonotonic potentials?

Lunar precursor effects in the solar wind and terrestrial magnetosphere

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