A Quantitative Model for Magnetic Shielding of Lunar Polar Ice: BowShock Formation, Streamline Deflection, and Testable Predictions
Authors/Creators
- 1. Independent Researcher
Description
This preprint presents a quantitative model demonstrating how weak crustal magnetic anomalies near the lunar poles form localized mini-magnetospheres that shield permanently shadowed regions from solar-wind sputtering. Using SI-consistent plasma physics, bow-shock geometry, and streamline deflection analysis, we show that even 100–200 nT fields can reduce ion flux by factors of 5–10, leading to the long-term accumulation of polar water ice.
The model predicts specific spatial patterns of ice retention, including comet-tail shadows and asymmetric distributions within craters, and offers five testable predictions using existing LRO, Kaguya, and LEND data. This work provides a causal, predictive explanation for the correlation observed by Hood et al. (2022) and proposes a physical mechanism for the south-to-north polar ice asymmetry.
With upcoming missions such as VIPER and Lunar Vertex targeting polar volatiles, this framework offers a timely and testable hypothesis for mission planners and data analysts.
Notes
How to Read This Paper
This paper is structured so that a reader can enter at different levels depending on what they care about—magnetic fields, plasma flow, ice accumulation, or testable predictions. The physics builds layer by layer, but you don’t need to read every section to follow the main idea.
If you want the big picture (5 minutes):
Read Sections 1–2 and 6.10–6.11.
These explain the paradox, the missing physics, and the full causal chain from magnetic fields → bow shocks → ice.
If you want to verify the plasma physics (20 minutes):
Focus on Section 2.
Here you’ll find the core derivations:
SI-consistent pressure balance
grazing-incidence dynamic pressure
standoff-distance scaling
Larmor-radius steering
All equations are dimensionally checked, and every input parameter is given in SI units to avoid cgs/SI confusion.
If you want to understand the geometry of protection (15 minutes):
Read Section 3.
This is where the streamline deflection picture is developed:
comet-tail shadow shapes
crater-specific mapping (Shoemaker)
multi-anomaly interference
how the shadow shifts with lunar orbit
This section is the bridge between magnetism and ice distribution.
If you want to check the ice budget (25 minutes):
Go to Section 4, where sputtering, delivery, and mixing are quantified:
unprotected sputtering removes ~9 m over 3.5 Gyr
magnetic protection cuts this by 5–10×
delivery gives ~6–12 m
protected zones accumulate 5–11 m; unprotected zones only 0–3 m
Everything is computed with transparent units and conservative assumptions.
If you want to test the model yourself:
Section 5 lists five falsifiable predictions that can be checked with existing LRO/Kaguya data:
ice–temperature spatial offset
Shoemaker vs Haworth contrast
comet-tail morphology
south–north asymmetry
sharp lateral gradients across shadow boundaries
These are designed for direct student replication.
If you want the implications and open questions:
Section 6 places the results into broader context:
why previous explanations failed
why south pole has more ice
mission planning implications
relevance to Mercury, Ceres, and tidally locked exoplanets
remaining unknowns in polar magnetism
If you want to reproduce the calculations:
Appendix “Reproducible Calculation Templates” gives pseudocode for:
pressure balance
grazing-incidence scaling
standoff distance
Larmor radius
sputtering loss
Files
A Quantitative Model for Magnetic Shielding of Lunar Polar Ice.pdf
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