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All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Rarefied gas dynamic effects on mass spectrometric studies of upper planetary atmospheres

Results are presented of measurements obtained with an open-source mass spectrometer both in earth orbit and in a laboratory molecular beam facility. The mass spectrometer/ion source combination was developed in the laboratory to be operable in either of two modes by altering ion extraction potential on ground command, i.e., as a stagnation cavity or to respond only to the incoming molecules of the unperturbed atmosphere. Results indicate that the use of this open-source configuration and dual-mode capability, allied with both standard static calibration and dynamic calibration using high-speed molecular beam techniques in the laboratory, allows collection of useful data on aeronomy of the upper atmosphere of planets and comet tails.

French, J. B.↗
DOE OSTI2026

Analysis of RF Sheath-Driven Tungsten Erosion at RF Antenna in the WEST Tokamak

This study applies the newly developed STRIPE (Simulated Transport of RF Impurity Production and Emission) framework to analyze tungsten (W) erosion at RF antenna structures in the WEST tokamak. STRIPE integrates SolEdge3x for edge plasma backgrounds, COMSOL for 3D RF sheath potentials, RustBCA for sputtering yields, and GITR for impurity transport and ion energy–angle distributions. Building on prior work by Kumar et al. (2025) Nuclear Fusion, 65, 076039, which validated STRIPE for WEST ICRH discharge #57877, the present study provides a spatially resolved assessment of gross W erosion at both Q2 antenna limiters under ohmic and ICRH conditions. Simulations using 2D SolEdge3x profiles in COMSOL capture rectified sheath potentials exceeding 300 V, leading to strong upper-limiter localization. Both poloidal and toroidal asymmetries are observed and attributed to RF sheath effects, with modeled erosion patterns deviating from experiment—highlighting sensitivity to sheath geometry and plasma resolution. Erosion is driven primarily by high-charge-state oxygen ions (O6+–O8+), while D+ plays a negligible role. Assuming a plasma composition of 1% oxygen and 98% deuterium, STRIPE predicts a 30-fold increase in gross W erosion from ohmic to ICRH phases, consistent with a >25-fold rise in W-I (400.9 nm) brightness. Quantitative agreement is within 5% in the ohmic phase and 30% under ICRH, demonstrating predictive capability. Importantly, the study shows that the magnitude of ICRH-driven W erosion depends strongly on the concentration of light impurities (O, B, N, C), which drive sputtering through high charge states. Cleaner plasma conditions with reduced impurity content are therefore expected to substantially mitigate antenna W sources in WEST and other toroidal fusion devices. These findings establish STRIPE as a predictive framework for RF-induced plasma–material interactions and support its application to reactor-scale antenna design.

Kumar, Atul [ORNL] (ORCID:0000000277475210)↗
DOE OSTI2025

Erosion of high-Z refractory coatings for helicon plasma source window

Proto-MPEX (Materials Plasma Exposure eXperiment), a linear plasma device (LPD), using a high power radio frequency (RF) (⩾100 kW, 13.56 MHz) helicon plasma source, has suffered RF sheath-induced window erosion. The sputtered impurities from the window surface transport toward the downstream target affecting plasma-material interaction studies. The rectified sheath voltage formed was high enough to cause window erosion by light ions due to its low-Z components (e.g. Si 3 N 4 and AlN). Hence, we are proposing impurity mitigation strategies, which involve the application of a Faraday screen to lower the rectified sheath voltage and the application of high-Z refractory coatings on the existing window plasma-facing surface. In this work, we report the erosion of two different coatings, i.e., tantalum oxide (Ta 2 O 5 ) and hafnium oxide (HfO 2 ) on a silicon nitride (Si 3 N 4 ) window material under conditions of low-energy deuterium (D) ion impact, well below the Ta 2 O 5 sputtering energy threshold (i.e. 250 eV). The test samples were RF-biased and exposed to a high D-ion fluence (∼10 26 m −2 ) in Plasma Interaction with Surface Component Experimental Station (PISCES-A) LPD. The experimentally measured sputtering yields of the high-Z refractory coatings below the sputtering energy threshold of Ta 2 O 5 indicate an increased erosion due to the plasma impurities, especially due to oxygen. Improving the vacuum level could reduce the oxygen impurities and increase the lifespan of the coated helicon window for plasma operation. Post-surface analysis indicates no preferential erosion of oxygen or enrichment of the high-Z surface component. This is likely due to an effective energy transfer from the impurity ion for sputtering of the high-Z component in the coating. With the reduced rectified sheath voltage at the window surface and improved vacuum conditions, the proposed high-Z refractory coatings offer a promising solution for reducing window erosion in future MPEX plasma operations at ORNL.

RF bias↗
DOE OSTI2023

Properties of Gaseous Deprotonated L-Cysteine S-Sulfate Anion [cysS-SO3]−: Intramolecular H-Bond Network, Electron Affinity, Chemically Active Site, and Vibrational Fingerprints

L-cysteine S-sulfate, Cys-SSO3H, and their derivatives play essential roles in biological chemistry and pharmaceutical synthesis, yet their intrinsic molecular properties have not been studied to date. In this contribution, the deprotonated anion [cysS-SO3]− was introduced in the gas phase by electrospray and characterized by size-selected, cryogenic, negative ion photoelectron spectroscopy. The electron affinity of the [cysS-SO3]• radical was determined to be 4.95 ± 0.10 eV. In combination with theoretical calculations, it was found that the most stable structure of [cysS-SO3]− (S1) is stabilized via three intramolecular hydrogen bonds (HBs); i.e., one O-H……N between the -COOH and -NH2 groups, and two N-H……O HBs between -NH2 and -SO3, in which the amino group serves as both HB acceptor and donor. In addition, a nearly iso-energetic conformer (S2) with the formation of an O-H……N-H……O-S chain-type binding motif competes with S1 in the source. The most reactive site of the molecule susceptible for electrophilic attacks is the linkage S atom. Theoretically predicted infrared spectra indicate that O-H and N-H stretching modes are the fingerprint region (2800 to 3600 cm−1) to distinguish different isomers. The obtained information lays out a foundation to better understand the transformation and structure–reactivity correlation of Cys-SSO3H in biologic settings.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1999

Energetic Neutral Atom Imaging at Low Altitudes from the Swedish Microsatellite Astrid: Images and Spectral Analysis

Observations of energetic neutral atoms (ENA) in the energy range 26- 52 keV are reported from four occasions during geomagnetically disturbed periods. The data were acquired by the ENA imager flown on the Swedish microsatellite Astrid in a 1000 km circular orbit with 83 deg inclination. The ENA imager separates charged particles from neutrals through an electrostatic deflection system in the energy range between 0.1 and 114 keV. ENA images obtained from vantage points in the polar cap and in the afternoon magnetic local time (MLT) hours looking into the antisunward hemisphere show intense ENA fluxes (approx. 10(exp 4)/sq cm sr s over 26-37 keV) coming from the dusk region and low altitudes (approx. 300 km). The morphology shows no relation to local magnetic field excluding the possibility of charged particle detection. It is concluded that the source of these ENAs are precipitating/mirroring ions from the ring current/trapped radiation interacting with the exobase on auroral L-shells and in the dusk region. The observed ENA fluxes show a relation with Kp and Dst geomagnetic indices. The observed ENA spectrum from a geomagnetic storm on February 8, 1995, is investigated in more detail and compared to the parent ion spectrum obtained by the Defense Meteorological Satellite Project (DMSP) satellite, Fl2, during the same period on L = 6 +/- 2 around dusk. The observed ENA spectral slope is used to derive the parent ion spectral temperature. The derived ion temperatures range is 3.0 - 6.0 keV for H and 4.5 - 8.5 keV for O. The higher of these ion temperatures comes closest in agreement to the extrapolated DMSP spectrum leading us to favor O over H as the species of the detected ENAS. It is shown that the detected ENAs must have been produced at L greater than or equal to 6 to reach the detector without atmospheric attenuation and that the main energy dependence of the ENA spectrum, apart from the parent ion spectrum, is governed by the energy dependence of the charge exchange cross section between ions and exospheric oxygen.

Brandt, Pontus C:son↗
DOE OSTI2022

Paving Pathways Toward Long–Life Graphite/LiNi 0.5 Mn 1.5 O 4 Full Cells: Electrochemical and Interphasial Points of View

The high-voltage spinel cathode LiNi 0.5 Mn 1.5 O 4 (LNMO) with no cobalt and low nickel content is promising for lithium-ion batteries due to its high energy and power densities, good thermal stability, and low cost. However, its high operating voltage (≈4.7 V) results in a decomposition of the electrolyte, severe chemical crossover, and deterioration of electrode-electrolyte interphases (EEIs), hindering its practical viability. It is demonstrated here that by electrochemically pre-cycling the graphite in an electrolyte containing 30 wt.% fluoroethylene carbonate, a robust LiF-rich artificial solid electrolyte interphase can be constructed for surface protection; on the other hand, an electrochemical pre-lithiation of Fe-doped LNMO serves as a lithium source for graphite at a full-cell voltage of 2.6 V. As a result, the full cells with the as-modified electrodes deliver a high capacity of 129 mA h g –1 with an excellent capacity retention of 93% after 200 cycles, vastly outperforming the full cells with fresh electrodes (120 mA h g –1 initial capacity with 78% retention). Lastly, pathways toward long-life graphite||LNMO full cells are pictured based on the inspirations from the electrochemical modifications and in-depth analyses of the EEIs in this study.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Machine-learning based approach to examine ecological processes influencing the diversity of riverine dissolved organic matter composition

Dissolved organic matter (DOM) assemblages in freshwater rivers are formed from mixtures of simple to complex compounds that are highly variable across time and space. These mixtures largely form due to the environmental heterogeneity of river networks and the contribution of diverse allochthonous and autochthonous DOM sources. Most studies are, however, confined to local and regional scales, which precludes an understanding of how these mixtures arise at large, e.g., continental, spatial scales. The processes contributing to these mixtures are also difficult to study because of the complex interactions between various environmental factors and DOM. Here we propose the use of machine learning (ML) approaches to identify ecological processes contributing toward mixtures of DOM at a continental-scale. We related a dataset that characterized the molecular composition of DOM from river water and sediment with Fourier-transform ion cyclotron resonance mass spectrometry to explanatory physicochemical variables such as nutrient concentrations and stable water isotopes ( 2 H and 18 O). Using unsupervised ML, distinctive clusters for sediment and water samples were identified, with unique molecular compositions influenced by environmental factors like terrestrial input and microbial activity. Sediment clusters showed a higher proportion of protein-like and unclassified compounds than water clusters, while water clusters exhibited a more diversified chemical composition. We then applied a supervised ML approach, involving a two-stage use of SHapley Additive exPlanations (SHAP) values. In the first stage, SHAP values were obtained and used to identify key physicochemical variables. These parameters were employed to train models using both the default and subsequently tuned hyperparameters of the Histogram-based Gradient Boosting (HGB) algorithm. The supervised ML approach, using HGB and SHAP values, highlighted complex relationships between environmental factors and DOM diversity, in particular the existence of dams upstream, precipitation events, and other watershed characteristics were important in predicting higher chemical diversity in DOM. Our data-driven approach can now be used more generally to reveal the interplay between physical, chemical, and biological factors in determining the diversity of DOM in other ecosystems.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1975

A composition analyzer for microparticles using a spark ion source

Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the element of both detector and particle materials. The total extracted ion currents was typically 10A within a period of 100ns, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes, or by nuclear bomb explosions.

Auer, S. O.↗
NASA NTRS1998

Spatial Distribution of Ionospheric Plasma and Field Structures in the High-Latitude F Region

Ion density and velocity measurements from the Dynamics Explorer 2 (DE 2) spacecraft are used to obtain the average magnetic local time versus invariant latitude distribution of irregularities in the high-latitude F region ionosphere. To study the small-scale structure and its relationship to background conditions in the ionosphere, we have formed a reduced database using 2-s (approx. = 16 km) segments of the ion density and velocity data. The background gradients associated with each 2-s segment and the spectral characteristics, such as power at 6 Hz (approx. = 1.3 km) and spectral index, are among the reduced parameters used in this study. The relationship between the observed plasma structure and its motion is complex and dependent on the externally applied fields as well as locally generated plasma structure. The evolution of plasma structures also depends critically on the conductivity of the underlying ionosphere. Observations indicate an enhancement of irregularity amplitudes in two spatially isolated regions in both the ion density and the velocity. Convective properties seem to play a more important role in winter hemisphere where smaller-scale structures are maintained outside the source regions. (Delta)V irregularity amplitudes are enhanced in the cusp and the polar cap during northward interplanetary magnetic field regardless of season. The power in (Delta)V is usually higher than that associated with local polarization electric fields, suggesting that the observed structure in (Delta)N/N is strongly influenced by (Delta)V structure applied to large density gradients.

Kivanc, O.↗
DOE OSTI2025

Geobacter sulfurreducens Immobilized Boron-Doped Diamond Electrodes for Uranium(VI) in Water Electrochemical Bioremediation

The proliferation of nuclear science and technology has resulted in an increase in nuclear waste containing uranium, posing significant risks to both human and environmental health. This study proposes the use of Geobacter sulfurreducens (G. sulfurreducens) modified boron-doped diamond electrodes to facilitate the reduction and removal of uranium(VI) from aqueous media. The bioremediation process involves electrochemically immobilizing the bacteria on a boron-doped diamond electrode (BDD). The immobilization process requires applying reduction potentials ranging from −0.40 to −0.70 V (vs Ag/AgCl (3 M NaCl)), with −0.60 V identified as the optimal potential for effective bacterial modification. The uranium source is provided by a 2.0 mM uranyl acetate solution in G. sulfurreducens growth medium. Scanning electron microscopy (SEM) reveals a highly uniform layer of uranium on the electrode surface. Energy-dispersive X-ray fluorescence spectroscopy (EDS) and cyclic voltammetry (CV) studies confirm the presence of uranium in the system. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) successfully elucidate the reduction process of U(VI) to predominantly U(IV) using a bacteria-electrode coupled system. Additionally, a comparison is made with the electrochemical removal of uranyl ions using the electrodeposition method on unmodified BDD. Results demonstrate the presence of three uranium oxide species (UO 2 , UO 3 , and U 3 O 8 ) on the BDD electrode after experimentation, in contrast to the G. sulfurreducens/BDD assembly, which achieves the predominant reduction of UO 2 2+ to UO 2 with a small quantity of UO 3 as the final species. This study highlights the efficient electrochemical removal of uranyl ions from aqueous media at the G. sulfurreducens/BDD interface through chronoamperometry, presenting a promising approach for remediating sites contaminated with radioactive materials. The findings contribute to the exploration of sustainable alternatives for managing nuclear waste, emphasizing the potential of this electrochemical bioremediation strategy.

Bacteria↗
DOE OSTI2020

Rational Design and Synthesis of Hierarchical Porous Mn–N–C Nanoparticles with Atomically Dispersed MnNx Moieties for Highly Efficient Oxygen Reduction Reaction

Developing transition-metal excluding iron and cobalt–nitrogen–carbon (M–N–C) electrocatalysts for the oxygen reduction reaction (ORR) is critical to substantially promote the development of precious-metal-free metal–air batteries and fuel cells. In the work, Mn–N–C nanoparticles with atomically dispersed MnNx moieties were synthesized by pyrolyzing Mn-ion–dual-pyridine coordinated complex, which was obtained via a simple condensation reaction between 2,6-diamino-pyridine and 2,6-diacetyl-pyridine with MnCl 2 as the Mn source. The precursor features with a characteristic structure of dual-pyridine ligand, which possesses a strong coordinating capability for Mn 2+ , facilitating the formation of highly dispersed nitrogen-coordinated Mn sites (MnN x ). Attributed to the highly active atomic MnN x sites, hierarchical pore structure, and high surface area of the Mn–N–C derived from the new precursor, it exhibits outstanding ORR performance in 0.1 M KOH with an almost direct four-electron reaction path and high selectivity of O 2 into H 2 O (low H2O2 production <3.5%). The half-wave potential of Mn–N–C is 0.88 V vs RHE, which is 20 mV higher than that of commercial Pt/C catalyst and reaches to the level of Fe–N–C catalyst obtained by the same method. Meanwhile, the feasibility of Mn–N–C for practical application is validated by its higher-performance power output in Zn–air battery with a maximum power density of 132 mW cm –2 compared to that of Pt/C (121 mW cm –2 ) using the same catalyst loading of 1.0 mg cm –2 . This work develops a convenient route to develop non-Fe or Co–N–C electrocatalyst for the ORR.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Energetic-particle abundances in impulsive solar flare events

We report on the abundances of energetic particles from impulsive solar flares, including those from a survey of 228 He-3 rich events, with He-3/He-4 is greater than 0.1, observed by the International Sun Earth Explorer (ISEE) 3 spacecraft from 1978 August through 1991 April. The rate of occurrence of these events corresponds to approximately 1000 events/yr on the solar disk at solar maximum. Thus the resonant plasma processes that enhance He-3 and heavy elements are a common occurrence in impulsive solar flares. To supply the observed fluence of He-3 in large events, the acceleration must be highly efficient and the source region must be relatively deep in the atmosphere at a density of more than 10(exp 10) atoms/cu cm. He-3/He-4 may decrease in very large impulsive events because of depletion of He-3 in the source region. The event-to-event variations in He-3/He-4, H/He-4, e/p, and Fe/C are uncorrelated in our event sample. Abundances of the elements show a pattern in which, relative to coronal composition, He-4, C, N, and O have normal abundance ratios, while Ne, Mg, and Si are enhanced by a factor approximately 2.5 and Fe by a factor approximately 7. This pattern suggests that elements are accelerated from a region of the corona with an electron temperature of approximately 3-5 MK, where elements in the first group are fully ionized (Q/A = 0.5), those in the second group have two orbital electrons (Q/A approximately 0.43), and Fe has Q/A approximately 0.28. Ions with the same gyrofrequency absorb waves of that frequency and are similarly accelerated and enhanced. Further stripping may occur after acceleration as the ions begin to interact with the streaming electrons that generated the plasma waves.

Reames, D. V.↗
NASA NTRS1975

Composition analyzer for microparticles using a spark ion source

Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the elements of both detector and particle materials. The total extracted ion current was typically 10 A within a period of 100 nsec, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes or by nuclear bomb explosions.

Auer, S.↗
NASA NTRS1991

Atomic oxygen beam source for erosion simulation

A device for the production of low energy (3 to 10 eV) neutral atomic beams for surface modification studies is described that reproduces the flux of atomic oxygen in low Earth orbit. The beam is produced by the acceleration of plasma ions onto a negatively biased plate of high-Z metal; the ions are neutralized and reflected by the surface, retaining some fraction of their incident kinetic energy, forming a beam of atoms. The plasma is generated by a coaxial RF exciter which produces a magnetically-confined (4 kG) plasma column. At the end of the column, ions fall through the sheath to the plate, whose bias relative to the plasma can be varied to adjust the beam energy. The source provides a neutral flux approximately equal to 5 x 10(exp 16)/sq cm at a distance of 9 cm and a fluence approximately equal to 10(exp 20)/sq cm in five hours. The composition and energy of inert gas beams was diagnosed using a mass spectometer/energy analyzer. The energy spectra of the beams demonstrate energies in the range 5 to 15 eV, and qualitatively show expected dependences upon incident and reflecting atom species and potential drop. Samples of carbon film, carbon-based paint, Kapton, mylar, and teflon exposed to atomic O beams show erosion quite similar to that observed in orbit on the space shuttle.

Cuthbertson, J. W.↗
NASA NTRS1990

Atomic oxygen beam source for erosion simulation

A device for production of low-energy (5-10 eV) neutral atomic beams for surface modification studies, which recreates the flux of atomic oxygen in LEO, is described. The beam is produced by acceleration of plasma ions onto a negatively biased plate of high-Z metal; the ions are neutralized and reflected by the surface, retaining a large fraction of their incident kinetic energy, forming a beam of atoms. The device is based on a magnetically confined (3-4 kG) coaxial plasma source and the atom energy can be varied by adjusting the bias voltage. The source provides a neutral flux of roughly 5 x 10 to the 16th/sq cm/s at a distance of 10 cm and a fluence of roughly 10 to the 21st/sq cm in five hours. The source has been characterized with plasma diagnostics and by measuring the energy of an atomic argon beam using a mass spectrometer. Samples of carbon film, carbon-based paint, Kapton, Mylar, and Teflon exposed to atomic O beams show erosion quite similar to those observed in orbit on the Space Shuttle.

Cuthbertson, J. W.↗
NASA NTRS1996

Far-Infrared Spectroscopy of Planetary Nebulae with the KAO

We present new far-infrared line observations of the planetary nebulae (PNs) NGC 7027, NGC 7009, and NGC 6210 obtained with the Kuiper Airborne Observatory (KAO). The bulk of our data are for NGC 7027 and NGC 7009, including [Ne(V)] 24 micrometers, [O(IV)] 26 micrometers, [O(III)] (52, 88) micrometers, and [N(III)] 57 micrometers. Our data for [O(III)] (52, 88) and [N(III)] 57 in NGC 7027 represent the first measurements of these lines in this source. The large [O(III)] 52/88-micrometer flux ratio implies an electron density (cubic cm) of log N(sub e)[O(III)] = 4.19, the largest Ne ever inferred from these lines. We derive N(++)/O(++) = 0.394 +/- 0.062 for NGC 7027 and 0.179 +/- 0.043 for NGC 6210. We are able to infer the O(+3)/O(++) ionic ratio from our data. As gauged by this ionic ratio, NGC 7027 is substantially higher ionization than is NGC 7009 - consistent with our observation that the former produces copious [Ne(V)] emission while the latter does not. These data help characterize the stellar ionizing radiation field. From our [O(IV)] and [O(III)] fluxes, we are able to show that O(++) is by far the dominant oxygen ion in NGC 7009. As a result, the O/H abundance inferred using these data tends to corroborate the value found from UV/optical, collisionally excited lines. We determined accurate rest wavelengths for the [Ne(V)] 2s(2)2p(2)P(sub 1) to 2s(2)2p(2)3P(sub 0) (lambda(sub rest) = 24.316 +/- 0.008 micrometers) and [O(IV)] 2s(2)2p(2)P(sup 0, sub 3/2) to 2s(2)2p(2)P(sup 0, sub 1/2) (lambda(sub rest) = 25.887 +/- 0.007 micrometers) transitions from observations of one or both of the bright PNs NGC 7027 and NGC 7009. Our [O(IV)] value, to the best of our knowledge, is the most accurate direct determination of this lambda(sub rest). These new KAO data will be beneficial for comparison with ISO observations of these PNs.

Rubin, Robert H.↗
NASA NTRS2013

The Solar Connection of Enhanced Heavy Ion Charge States in the Interplanetary Medium: Implications for the Flux-Rope Structure of CMEs

We investigated a set of 54 interplanetary coronal mass ejection (ICME) events whose solar sources are very close to the disk center (within +/- 15deg from the central meridian). The ICMEs consisted of 23 magnetic-cloud (MC) events and 31 non-MC events. Our analyses suggest that the MC and non-MC ICMEs have more or less the same eruption characteristics at the Sun in terms of soft X-ray flares and CMEs. Both types have significant enhancements in ion charge states, although the non-MC structures have slightly lower levels of enhancement. The overall duration of charge-state enhancement is also considerably smaller than that in MCs as derived from solar wind plasma and magnetic signatures. We find very good correlation between the Fe and O charge-state measurements and the flare properties such as soft X-ray flare intensity and flare temperature for both MCs and non-MCs. These observations suggest that both MC and non-MC ICMEs are likely to have a flux-rope structure and the unfavorable observational geometry may be responsible for the appearance of non-MC structures at 1 AU. We do not find any evidence for an active region expansion resulting in ICMEs lacking a flux-rope structure because the mechanism of producing high charge states and the flux-rope structure at the Sun is the same for MC and non-MC events.

flux rope↗
DOE OSTI2022

Mechanism for the Efficient Homogeneous Nucleation of Ice in a Weakly Ionized, Ultracold Plasma

Abstract It is proposed that the rapid observed homogeneous nucleation of ice dust in a cold, weakly ionized plasma depends on the formation of hydroxide (OH − ) by fast electrons impacting water molecules. These OH − ions attract neutral water molecules because of the high dipole moment of the water molecules and so hydrates of the form (OH) − (H 2 O) n are formed. The hydrates continuously grow in the cold environment to become macroscopic ice grains. These ice grains are negatively charged as a result of electron impact and so continue to attract water molecules. Because hydroxide is a negative ion, unlike positive ions, it does not suffer recombination loss from collision with plasma electrons. Recombination with positive ions is minimal because positive ions are few in number (weak ionization) and slow-moving as result of being in thermal equilibrium with the cold background gas.

79 ASTRONOMY AND ASTROPHYSICS↗