Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2509.05644

Non-Linear Solar EUV-Driven Sodium Release from the Lunar Surface: A Contrast to the Linear PSD Model

A Devaraj·S Narendranath·Sreeja S Kartha·M Sarantos·Akhil Krishna R·Blesson Mathew·T Sivarani·S Nidhi·P Anbazhagan·G Selvakumar
View original source ↗Read source document ↗Export metadata ↓

Abstract

The correlation between solar Extreme Ultra-Violet (EUV) radiation above 8.8 eV and the release of sodium from the lunar surface via photon-stimulated desorption (PSD) is investigated. We use simultaneous measurements of EUV photon flux and Na optical spectral line flux ($F_{Na}$) from the lunar exosphere. Data were acquired with the high-resolution (R$\sim$72000) Echelle Spectrograph on the 2.34-m Vainu Bappu Telescope during the lunar first quarter (January-March 2024), observing $Na\,I$ D2 and D1 flux at altitudes below $\sim590\,km$ from the surface. Simultaneous EUV and FUV measurements were acquired from the GOES-R Series Extreme Ultraviolet Sensor (EUVS), while NUV data were obtained from the Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) aboard the ISS. We correlated $F_{Na}$ with EUV photon flux from EUVS across six bands spanning $256-1405\,\text{Å}$ (48.5-8.8 eV) and NUV (2000-4000 $\text{Å}$) from TSIS-1. A non-linear rise in lunar exospheric sodium with increasing EUV and FUV fluxes was observed, contrasting with previous linear PSD models. The EUV radiation above 10 eV drives sodium release, with 256-304 $\text{Å}$ wavelengths as dominant contributors. Additionally, the NUV flux and $F_{Na}$ are positively correlated, indicating the role of sodium release. The zenith column density averages $3.3\times10^{9}$ atoms cm$^{-2}$, with Characteristic temperatures averaging at $\sim$6700K and scale heights of $\sim$1500 km. Elevated temperatures and sodium densities during solar activity suggest enhanced Na release during flares. These results emphasize the need for a revised PSD model above 8.8 eV and improved constraints on the PSD cross-section.

Explore related subjects

astro-ph.EPastro-ph.SR

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A Devaraj, S Narendranath, Sreeja S Kartha, M Sarantos, Akhil Krishna R, Blesson Mathew, T Sivarani, S Nidhi, P Anbazhagan, G Selvakumar. 2025-09-06. Non-Linear Solar EUV-Driven Sodium Release from the Lunar Surface: A Contrast to the Linear PSD Model. https://doi.org/10.1093/mnras%2Fstaf1447

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Volcanic Satellites and Ion Escape in the Magnetospheres of Ultra-Cool and Brown Dwarf Stars

Radio emissions at $\sim$ GHz frequencies of ultra-cool dwarf and brown dwarf stars suggest the presence of radiation belts not unlike Jupiter's. We investigate the possibility the inferred magnetospheric plasma at the primary star is sourced by an active planet or via ion escape modeled as a weak ionospheric outflow. We consider indirect methods to estimate the magnetospheric plasma mass flow from auroral radio emission and apply them to the ultra-cool dwarf LSR J1835+3259. We find that an ionospheric outflow is a viable source of the order of $10^{5}$ kg s$^{-1}$, if the ionospheric effective Pedersen conductance is lower than $\sim 0.02$ mho. On the other hand, a tidally-heated volcanic satellite with the same mass and radius as Io and an orbit with a semimajor axis lower than about $10$ stellar radii, whose eccentricity ($e \sim 10^{-3}$) is maintained by perturbations by other planets in the system, is found to be a viable source of magnetospheric plasma without strong limitations on the ionospheric conductance. The volcanic satellite scenario is also naturally in sync with the recent finding that ultra-cool dwarfs with distant substellar or stellar companions are remarkably more likely to be detected as radio emitters.

astro-ph.EP↗
arXiv2026

Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon

Venus possesses no natural satellite, raising the question whether a formed moon could have survived. We explore the tidal evolution of a Venus-moon system, coupling Venus's spin to the satellite's orbit under tides from the moon and Sun. We survey spin period ($P_0 = 5$--100~hr), moon mass ($M_m = 0.01$--$10~M_{\rm Moon}$), eccentricity, quality factor, and initial semi-major axis under both constant-$Q$ and constant time lag models. Survival depends on competition between outward migration ($\propto M_m$) and synchronous radius expansion ($\propto M_m^2$): for circular orbits around rapidly spinning Venus ($P_0 \lesssim 12$~hr), a lunar-mass satellite survives the age of the Solar System in both models. For $P_0 \lesssim 10$~hr, eccentricity pumping can destabilize low-mass satellites, while for $P_0 \gtrsim 15$~hr or $M_m \gtrsim 2~M_{\rm Moon}$ the synchronous radius overtakes the orbit and drives Roche destruction within $\sim$0.03--1.7~Gyr in the constant-$Q$ model. The constant time lag model instead permits quasi-synchronous survival for massive moons at fast spin. Explaining Venus's present state requires satisfying two constraints simultaneously: loss of the satellite and despinning of an initially rapid rotator. Both are met only within a restricted region of parameter space, favoring moderate post-impact spin periods and lunar-to-super-lunar masses. Giant impact simulations predict spin periods $\gtrsim$12~hr for Venus's present rotation, placing a lunar-mass satellite at the survival boundary. For last-impact conditions within this region, the present absence of a Venusian satellite arises through tidal evolution alone; a subsequent catastrophic stripping event, while capable of removing a moon, is not required.

astro-ph.EP↗
arXiv2026

Evidence for an Extended Hydrogen Outflow on WASP-12 b

Recent observations of atmospheric escape from planets orbiting early-type stars indicate that planets with higher Roche filling factors have significantly higher mass loss rates. For three of these planets, full-orbit observations have revealed the presence of large leading and trailing tails of escaping planetary material. These 3D outflow geometries encode information about the underlying outflow physics, and can also be used to constrain their stellar wind properties and to predict their long-term orbital evolution. We present new evidence for extended H$α$ and H$β$ absorption from escaping hydrogen for a fourth planet, WASP-12 b. We observed WASP-12 b with the Keck Planet Finder on Keck I over a period of approximately eight hours centered on the transit. We find a H$α$ and H$β$ absorption signal in the stellar rest frame that is strongest during the transit (H$α$ amplitude: $2.66\pm0.25\%$, H$β$ amplitude: $2.88\pm0.43\%$), with evidence of both pre- and post-transit absorption. This measurement is consistent with outflow models where the escaping gas overflows the planet's Roche lobe and is advected into the stellar rest frame before being tidally sheared into extended tails. This outflow behavior is qualitatively similar to previous H$α$ observations of this planet as well as observations of extended outflows from other gas giants orbiting early-type stars.

astro-ph.EP↗