New preprints map hidden flows on Mars, Mercury, icy moons and glaciers
Five preprints posted Oct. 15 to the ESS Open Archive measure motion nobody can watch directly: melt shifting inside Mars, plasma thickening at Mercury, oceans read via magnetism on Europa and Ganymede, solar-wind turbulence tied to the averaging window, and meltwater skewing glacier radar.
- A preprint by Jiachang Zhang models a 100-km-thick Martian melt layer and estimates about 2.62 × 10¹⁰ kg of north-south mass exchange per orbit from solar differential gravity, with a maximum mean equivalent thickness difference of about 0.14 μm whose polarity depends on orbital phase. Self-reported m:…8771
- A preprint by Yong Wei, combining MESSENGER data with 3D hybrid simulations, finds Mercury's plasma sheet under northward IMF roughly doubles in density (7.3 vs 3.7 cm⁻³) and thickens (1.53 vs 0.58 R_M) while cooling (11 vs 18 MK) — treated as an intrinsic feature of solar-wind interaction with dipolar magnetospheres. Self-reported m:…8878
- Synthetic experiments by Olivier G. Witasse show the vertical structure of toroidal flow in a subsurface ocean is reconstructible in the upper parts of Europa's ocean but not on Ganymede, while general poloidal flow characteristics are recoverable on both moons under certain a priori assumptions. No real observational data were used. Self-reported m:…3182
- William H. Matthaeus's preprint, using Parker Solar Probe encounters 1–19, finds magnetic fluctuation energies rise systematically with larger averaging windows while the distribution of sub-Alfvénic intervals stays relatively insensitive to averaging scale; effective magnetic correlation time shrinks to several minutes near MA = 1. Self-reported m:…8238
- Dustin M. Schroeder's preprint shows as little as 0.2% oriented meltwater by volume can modify radar anisotropy created by solid crystallographic orientation fabrics in temperate ice, and at 1% melt fraction the horizontal permittivity anisotropy changes by a factor of more than 20 — so COF-only interpretations may mispredict subsurface ice flow. Self-reported m:…8155
The thread: flows nobody can see
Five preprints take up one shared problem: how to measure motion that no instrument can observe head-on. One models melt shifting inside Mars under the Sun's differential gravity. Another finds Mercury's plasma sheet growing colder and denser under northward magnetic fields. A third tests whether magnetism can map oceans beneath the ice of Europa and Ganymede. A fourth shows that solar-wind turbulence readings change with the chosen averaging window. And a fifth warns that tiny fractions of meltwater can skew radar readings of glacier ice. m:…8771 m:…8878 m:…3182 m:…8238 m:…8155
All five are preprints, so every number below rests on the authors' own reported results, not on independent verification. What links them is the reporting question: what did these new measurements reveal about flows hidden from direct observation? m:…8771
Mars: an orbit stirring a buried melt layer
Jiachang Zhang's preprint models a 100-km-thick melt layer beneath the Martian crust and asks how solar differential gravity moves mass between hemispheres over each orbit. Coupling orbital dynamics with basal crystallization models, the study estimates roughly 2.62 × 10¹⁰ kg of north-south mass exchange per orbit, with a maximum north-south mean equivalent thickness difference of about 0.14 μm whose polarity depends on orbital phase. m:…8771
The result is a quantitative constraint for models of Martian hemispheric asymmetry: a phase-dependent hemispheric mass record that planetary scientists and geophysicists can test against ideas about how the asymmetry is later amplified. m:…8771
Mercury: a colder, denser plasma sheet
Yong Wei's preprint combines MESSENGER satellite data with 3D hybrid simulations to study Mercury's plasma sheet during northward interplanetary magnetic field events. Under northward IMF, the sheet's mean density roughly doubles from 3.7 to 7.3 cm⁻³, mean ion temperature falls from about 18 to 11 MK, and the sheet thickens from about 0.58 to 1.53 Mercury radii — a cold dense plasma sheet taking shape around the planet. m:…8878
The study treats this cold dense plasma sheet as an intrinsic feature of solar-wind interaction with dipolar magnetospheres, independent of a significant ionosphere, mirroring phenomena observed at Earth. That framing makes Mercury a useful test case for space-weather modeling of dipolar systems that lack substantial ionospheres. m:…8878
Europa and Ganymede: oceans read through magnetism
Olivier G. Witasse's preprint asks whether ocean-induced magnetic fields can constrain the flow geometry of subsurface oceans on icy moons, work aimed at magnetic-field inversion strategies for the Europa Clipper and Juice missions. The study is built entirely on synthetic experiments using magnetic field inversion — no real observational data were used. m:…3182
In those synthetic tests, the vertical structure of toroidal flow can be reconstructed in the upper parts of Europa's ocean, but the same vertical structure cannot be constrained on Ganymede. The difference traces to signal periodicity: Europa's periodic ocean-induced signal offers different sensitivity than Ganymede's stationary signal. m:…3182
More broadly, general characteristics of the poloidal flow — such as the number of convection cells and their size — can be recovered on both moons, provided certain a priori assumptions hold. m:…3182
Solar wind: the window changes the reading
William H. Matthaeus's preprint uses Parker Solar Probe data from encounters 1 through 19 to test how averaging intervals affect estimates of the solar wind Alfvén Mach number. Magnetic fluctuation energies increase systematically with larger averaging windows, while the distribution of sub-Alfvénic intervals proves relatively insensitive to the choice of averaging scale. m:…8238
Effective magnetic correlation time decreases with heliocentric distance and Alfvén Mach number, reaching values of several minutes near MA = 1. The practical takeaway for space-weather modelers and satellite operators: characterizing solar-wind turbulence and Alfvénic transitions consistently requires standardized, physically based temporal windows. m:…8238
Glacier radar: a little meltwater, a large skew
Dustin M. Schroeder's preprint uses numerical modeling to study how oriented interstitial melt — a meltwater orientation fabric — interacts with solid crystallographic orientation fabrics in temperate ice undergoing shear deformation. As little as 0.2% meltwater by volume is enough to modify anisotropy created by solid crystallographic fabrics, and at 1% melt fraction the horizontal permittivity anisotropy can change by a factor of more than 20. m:…8155
Radar interpretations that rely solely on crystallographic fabrics may therefore mispredict the extent of subsurface ice flow in temperate or salty regions — a caution for researchers and operators using radar sounding for cryospheric monitoring and subsurface characterization. m:…8155
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