Dependence of lunar surface charging on solar wind plasma conditions and solar irradiation

Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.; Burchill, J. K.; Collier, M. R.; Zimmerman, M. I.; Vondrak, R. R.; Delory, G. T.; Pfaff, R. F.

doi:10.1016/j.pss.2013.07.008

Cited by 97 publications

(49 citation statements)

References 61 publications

(92 reference statements)

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“…This may have been due to the fact that the observations on orbit 164 were over the lunar North Pole, rather than viewing closer to the lunar equator as occurred on orbit 66 and 273. However, this is not anticipated to be a significant factor for lunar surface charging and electrostatic lofting, which are primarily dependent on solar zenith angle [ Stubbs et al ., , ]. Therefore, consistent with the reanalysis of the Apollo coronal photography by Glenar et al .…”

Section: Discussionsupporting

confidence: 89%

Search for a high‐altitude lunar dust exosphere using Clementine navigational star tracker measurements

et al. 2014

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During the 1994 Clementine lunar mapping mission, portions of 25 orbits were dedicated to a search for lunar horizon glow (LHG) using the spacecraft star tracker navigation cameras. Previous putative detections of LHG were believed to result from forward scattering of sunlight by exospheric dust grains with radii ≈ 0.1 µm, observable above the limb from within the shadow of the Moon near orbital sunrise or sunset. We have examined star tracker image sequences from five Clementine orbits in which the limb occulted the Sun, and was at least partially shadowed from earthshine, minimizing the chance of stray light contamination. No LHG appears in the image data, or in any of the net brightness images, after subtraction of a reference zodiacal light model. However, some of the images display faint excess limb brightness that appears to be solar streamer structure. Therefore, we derive upper limits for the amount of dust in the lunar exosphere that could be hidden by these brightness fluctuations using a dust‐scattering simulation code and simple exponential dust profiles defined by surface concentration n0 and scale height H. Simulations using grains of radius 0.1 µm show that fluctuations in the observed excess brightness can be matched by a dust exosphere with a vertical column abundance n0H of 5–30 cm−2 and overlying mass <10−12 g cm−2. These dust upper limit estimates are highly dependent on assumed grain size due to the rapid increase in per‐grain brightness with grain radius.

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Section: Discussionsupporting

confidence: 89%

Search for a high‐altitude lunar dust exosphere using Clementine navigational star tracker measurements

et al. 2014

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“…Surface charging at Earth's Moon has been extensively investigated through spacecraft observations [ Halekas et al ., , , , , , ] and through theoretical studies [ Manka , ; Farrell et al ., ; Stubbs et al ., , ; Poppe and Horányi , ; Poppe et al ., ]. These studies have generally found that the dayside lunar surface is charged a few volts positive (~10 V) and that the lunar nightside and terminator regions reach strongly negative potentials (~ −100 to −200 V).…”

Section: Discussionmentioning

confidence: 99%

Detection of a strongly negative surface potential at Saturn's moon Hyperion

Nordheim

Jones

Roussos

et al. 2014

Geophysical Research Letters

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On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (∼ −200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator.

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“…We also assume the charge deposition layer to be infinitely planar [cf. Stubbs et al , ]. This is reasonable because the particle deposition occurs over regions whose length scales L are very large relative to the penetration depths (i.e., z ≪ L ).…”

Section: Double Charge Layer Modelmentioning

confidence: 99%

Deep dielectric charging of regolith within the Moon's permanently shadowed regions

Jordan

Stubbs

Wilson

et al. 2014

J. Geophys. Res. Planets

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Energetic charged particles, such as galactic cosmic rays (GCRs) and solar energetic particles (SEPs), can penetrate deep within the lunar surface, resulting in deep dielectric charging. This charging process depends on the GCR and SEP currents, as well as on the regolith's electrical conductivity and permittivity. In permanently shadowed regions (PSRs) near the lunar poles, the discharging timescales are on the order of a lunation (∼20 days). We present the first predictions for deep dielectric charging of lunar regolith. To estimate the resulting subsurface electric fields, we develop a data‐driven, one‐dimensional, time‐dependent model. For model inputs, we use GCR data from the Cosmic Ray Telescope for the Effects of Radiation on board the Lunar Reconnaissance Orbiter and SEP data from the Electron, Proton, and Alpha Monitor on the Advanced Composition Explorer. We find that during the recent solar minimum, GCRs create persistent electric fields up to ∼700 V/m. We also find that large SEP events create transient but strong electric fields (≥106 V/m) that may induce dielectric breakdown. Such breakdown would likely result in significant modifications to the physical and chemical properties of the lunar regolith within PSRs.

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Dependence of lunar surface charging on solar wind plasma conditions and solar irradiation

Cited by 97 publications

References 61 publications

Search for a high‐altitude lunar dust exosphere using Clementine navigational star tracker measurements

Search for a high‐altitude lunar dust exosphere using Clementine navigational star tracker measurements

Detection of a strongly negative surface potential at Saturn's moon Hyperion

Deep dielectric charging of regolith within the Moon's permanently shadowed regions

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