Data-driven modeling of Landau damping by physics-informed neural networks
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70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Chemical clocks: using otolith geochemistry to enhance estimation of age and growth of white hake (Urophycis tenuis)
The white hake (Urophycis tenuis) is a groundfish distributed throughout the Gulf of Maine. Catch advice is based on stock assessments done with age-based population dynamics models; however, otolith aging is challenging because of unclear growth increments. To address this concern, we compared the consistency of aging with counts of visual annuli to that of aging with cycles of elemental concentrations measured by using laser ablation inductively coupled plasma mass spectrometry. We tested the hypothesis that oscillations in both environmental conditions and internal physiology through time influence uptake of elements during otolith mineralization. Concentrations of manganese, in comparison with those of the other investigated trace elements (magnesium, strontium, and barium), had the most promising correlation with visual growth increments (~100% age agreement, ±1 year), offering an additional tool to enhance increment identification. In our examination of 550 otoliths collected during 2007–2021, we found that white hake lived a maximum of 10.3 years and exhibited sexual dimorphism in maximum length and age. By using generated von Bertalanffy growth functions, L(t)=110(1–e–0.113(t+0.45)) for males and L(t)=140(1–e–0.113(t–0.30)) for females (where L(t) is length at time t), size and age at maturity were calculated for males (37.4 cm in total length (TL), 3.3 years) and females (47.4 cm TL, 4.2 years). These results demonstrate that otolith geochemistry can be used to improve the accuracy and precision of the estimation of fish age and maturity, even for challenging species.
59 BASIC BIOLOGICAL SCIENCES↗
Investigation of conditions producing a dense plasma in a metallic chamber and its high frequency heating
Conditions producing dense plasma in metallic chamber and its high frequency heating
PLASMA HEATING↗
Experimental observation of quasi-linear mode coupling in a confined, hot-ion plasma
Quasi-linear mode coupling in confined hot-ion Penning discharge plasma, discussing externally imposed excitation and internally generated oscillations
Roth, J. R.↗
Vibrations of the earth's magnetic tail
The natural vibration period of the tail (regarded as bundle of magnetic line-of-force strings) and the characteristic time of recurrence of magnetospheric substorms are of the same order, suggesting the possibility of a relation between these phenomena. A model of the tail in the form of a plasma cylinder whose free boundary is immersed in the interplanetary plasma is examined. The nature of the natural oscillations of the tail excited by variations of the solar wind pressure is studied in this model. These vibrations have a total energy of approximately 10 to the 22nd power erg, which is sufficient to generate magnetospheric substorms.
Yershkovich, A. I.↗
The rate of occurrence of dayside Pc 3,4 pulsations - The L-value dependence of the IMF cone angle effect
When the angle of the IMF to the earth sun line is 15 deg or less, the occurrence rate of dayside Pc 3,4 pulsations in 7-8 times the average at L values of 2.4-2.8, and 2.2-3.5 times the average at L of 4-4.3. These waves disappear when the IMF is nearly at right angles to the sun-earth line. Such observations are consistent with a source originating in the waves upstream of the subsolar bow shock, which are transported by convection to the magnetopause. There, they couple to oscillations of magnetospheric field lines. Because the magnetospheric plasma's index of refraction decreases with radial distance except at the plasmapause, inwardly propagating waves should be refracted away from the radial direction. To reach low L values, the waves should therefore couple near the stagnation point and propagate nearly radially inwards. The streamline geometry and its connection to the foreshock region is illustrated for various IMF orientations, using a simple approximation to the magnetosheath flow field.
Russell, C. T.↗
Observation of reconnection phenomena at synchronous orbit
SCATHA satellite observations of large-amplitude magnetic field oscillations in the magnetosheath and in the associated plasma are studied. Large-amplitude variations in the magnetosheath magnetic field intensity with a quasi-period of 10 s were observed. Nearly static structures of high-beta plasma associated with the magnetic field minima and low-beta plasma associated with the magnetic field maxima were observed convecting toward the earth. The morphology of charged particle data for the transition between the magnetosphere and the magnetosheath for a northward magnetosheath magnetic field is presented. A convection electric field of about 9 mV/m was inferred from the spectral difference between solar and antisolar drifting ions in the magnetosheath near a magnetopause rotational discontinuity. A trapped component was observed in the magnetosheath plasma during both northward and southward magnetosheath magnetic fields. It is concluded that flux transfer events arise from the interaction of the earthward convecting plasma filaments with the magnetospheric magnetic field at the magnetopause.
Croley, D. R., Jr.↗
A Semianalytical Ion Current Model for Radio Frequency Driven Collisionless Sheaths
We propose a semianalytical ion dynamics model for a collisionless radio frequency biased sheath. The model uses bulk plasma conditions and electrode boundary condition to predict ion impact energy distribution and electrical properties of the sheath. The proposed model accounts for ion inertia and ion current modulation at bias frequencies that are of the same order of magnitude as the ion plasma frequency. A relaxation equation for ion current oscillations is derived which is coupled with a damped potential equation in order to model ion inertia effects. We find that inclusion of ion current modulation in the sheath model shows marked improvements in the predictions of sheath electrical properties and ion energy distribution function.
Bose, Deepak↗
The Nature of Standing Plasma Waves Following Fast Breakdown in Thunderstorms
Narrow bipolar events (NBEs) are produced by large-scale systems of streamer corona discharges that occur inside thunderstorms and radiate intensely at very-high frequencies. Here we examine 14 high-power NBEs recorded in Florida which are followed by a lasting oscillatory signal. We isolate the dominant frequencies of the oscillations using empirical mode decomposition methods, and cross-reference this information with the radiator size inferred from broadband interferometry. We conclude that the oscillations are evidence of a standing electromagnetic wave in the plasma cavity created by the preceding streamer system, that is, the cavity's fundamental mode with wavelength equal to twice the radiator length. Contrasting the dispersive and attenuation properties of these waves across several different events allows us to conclude that the cavity is filled with ions resulting in an average conductivity of 0.01–0.1 mS/m, which are left behind after the streamers decay via electron attachment to oxygen molecules.
58 GEOSCIENCES↗
SEPAC data analysis in support of the environmental interaction program
Data analyses of the Space Experiments with Particle Accelerators (SEPAC) data and computer modeling were conducted to investigate spacecraft environmental effects associated with injection of electron beams, plasma clouds, and neutral gas clouds from the Shuttle orbiter. The data analysis indicates that Extremely Low Frequency oscillations from 150 to 200 Hz were seen in the Langmuir probe current when the beam was fired in a continuous mode. The strongest oscillations occurred when the ambient pressure was augmented by neutral gas releases from the SEPAC plasma accelerator magnetoplasma-dynamic (MPD) arcjet. To understand the dependence of spacecraft charging potential on beam density and other plasma parameters, a two-dimensional electrostatic particle code was used to simulate the injection of electron beams from an infinite conductor into a plasma. The simulations show that the conductor charging potential depends critically on the reflection coefficient of the conductor surface, which is defined as the percentage of incident particles reflected by the conductor. The ionization effects on spacecraft charging were examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. The simulations also indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. It appears that the charge buildup at the beam stagnation point causes the beam radial expansion. A survey of the simulation results suggests that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. These results are useful for explaining the spacecraft charging phenomena observed during SEPAC experiments from Spacelab 1.
Lin, Chin S.↗
Optical design and synthetic analysis of the electron cyclotron emission imaging diagnostic of HL-2M tokamak
The electron cyclotron emission imaging (ECEI) diagnostic is a powerful tool to study the MHD and turbulent transport in magnetically confined fusion plasmas. In this work, the optical system including the local oscillator (LO) coupling and radio frequency (RF) receiving optics, has been designed and analyzed for the HL-2M ECEI diagnostic. The LO optics can illuminate the antenna array and drive the mixer diode to work efficiently, with more than 36% of the beam intensity for the channels which probe the plasma edge relative to those of channels which probe the plasma core. The RF optics aims at guiding the plasma emission signal to the antenna array. To meet different physical requirements, three types of field of view have been achieved for the plasma imaging, with zoom factors of around 1, 1.5 and 2, respectively. The focal surfaces are almost flat, with a maximum off-mapping (defined as the radial distance between the beam waists of the lower-/uppermost antennas and electron cyclotron emission layer) less than 2.5 cm, which can match the electron cyclotron emission layer quite well and suppress the image distortion in the plasma edge region. Furthermore, the impact of possible vibrations and installation error on the focal plane has been evaluated. In addition, the predefined MHD and turbulence perturbations are well reproduced by combining the optical simulation results and synthetic ECEI modeling, which further verifies the good performance of the RF optics.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Auxin-activated NADH oxidase activity of soybean plasma membranes is distinct from the constitutive plasma membrane NADH oxidase and exhibits prion-like properties
The hormone-stimulated and growth-related cell surface hydroquinone (NADH) oxidase activity of etiolated hypocotyls of soybeans oscillates with a period of about 24 min or 60 times per 24-h day. Plasma membranes of soybean hypocotyls contain two such NADH oxidase activities that have been resolved by purification on concanavalin A columns. One in the apparent molecular weight range of 14-17 kDa is stimulated by the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The other is larger and unaffected by 2,4-D. The 2,4-D-stimulated activity absolutely requires 2,4-D for activity and exhibits a period length of about 24 min. Also exhibiting 24-min oscillations is the rate of cell enlargement induced by the addition of 2,4-D or the natural auxin indole-3-acetic acid (IAA). Immediately following 2,4-D or IAA addition, a very complex pattern of oscillations is frequently observed. However, after several hours a dominant 24-min period emerges at the expense of the constitutive activity. A recruitment process analogous to that exhibited by prions is postulated to explain this behavior.
Non-NASA Center↗
Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in underdoped Bi2Sr2CaCu2O8+δ
ABSTRACT Superconducting phase transitions in two dimensions lie beyond the description of the Ginzburg-Landau symmetry-breaking paradigm for three-dimensional superconductors. They are Berezinskii-Kosterlitz-Thouless (BKT) transitions of paired-electron condensate driven by the unbinding of topological excitations, i.e. vortices. The recently discovered monolayers of layered high-transition-temperature (${{{T}}}_{{\rm C}}$) cuprate superconductor Bi2Sr2CaCu2O8+δ (Bi2212) meant that this 2D superconductor promised to be ideal for the study of unconventional superconductivity. But inhomogeneity posed challenges for distinguishing BKT physics from charge correlations in this material. Here, we utilize the phase sensitivity of scanning superconducting quantum interference device microscopy susceptometry to image the local magnetic response of underdoped Bi2212 from the monolayer to the bulk throughout its phase transition. The monolayer segregates into domains with independent phases at elevated temperatures below ${{{T}}}_{{\rm C}}$. Within a single domain, we find that the susceptibility oscillates with flux between diamagnetism and paramagnetism in a Fraunhofer-like pattern up to ${{{T}}}_{{\rm C}}$. The finite modulation period, as well as the broadening of the peaks when approaching ${{{T}}}_{{\rm C}}$ from below, suggests well-defined vortices that are increasingly screened by the dissociation of vortex-antivortex plasma through a BKT transition. In the multilayers, the susceptibility oscillation differs in a small temperature regime below ${{{T}}}_{{\rm C}}$, consistent with a dimensional crossover led by interlayer coupling. Serving as strong evidence for BKT transition in the bulk, we observe a sharp jump in phase stiffness and paramagnetism at small fields just below ${{{T}}}_{{\rm C}}$. These results unify the superconducting phase transitions from the monolayer to the bulk underdoped Bi2212, and can be collectively referred to as the BKT transition with interlayer coupling.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Measuring ionospheric electron density using the plasma frequency probe
During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes.
Jensen, Mark D.↗
Impact of edge harmonic oscillations on the divertor heat flux in NSTX
Previously, ELM-free and inter-ELM divertor peak heat flux reduction induced by an edge harmonic oscillation (EHO) was observed in NSTX (K.F. Gan et al., 2017 Nucl. Fusion 57 126053). This paper introduces new analysis of the EHO impact on the divertor heat flux. It was found that enhanced edge turbulence significantly altered the divertor heat flux footprint in NSTX H-modes, relative to ELM-free discharges. When the background edge fluctuation level was low, the EHO significantly increased the heat flux width and decreased the divertor peak heat flux. When the background edge fluctuation level was high, the EHO actually increased the divertor peak heat flux. As a result, it was also found that the heat flux width increased with increasing frequency of the EHO.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Generation of gamma radiation by a subterawatt ultrashort laser pulse: optimisation of preplasma and pulse duration
We report an experimental and numerical study of the acceleration of electrons in a plasma interacting with a subterawatt laser pulse (intensity of ∼3 × 10{sup 18} W cm{sup −2} at a pulse duration of 50 fs). A preplasma layer on the surface of a molybdenum target is formed by an additional laser pulse with a duration of 8 ns and an intensity of ∼2 × 10{sup 12} W cm{sup −2}. It is shown that an increase in the laser pulse duration to 1700 fs at a constant energy (and a proportional decrease in intensity) leads to an increase in the yield of bremsstrahlung γ-radiation by more than an order of magnitude when the nanosecond pulse is ahead of the femtosecond one by 15 − 25 ns. Interferometry data and results of diagnostics of optical and γ-radiation of a plasma demonstrate that the collisional ionisation of atoms by electrons oscillating in the field of such a laser pulse plays an essential role in the formation of electron density profile. The sensitivity of the described effect to the level of amplified spontaneous emission is determined, despite the nanosecond pulse impact. Numerical simulations show that at a large pulse duration, the acceleration of electrons is stipulated by the beaking of plasma waves excited during stimulated Raman scattering of laser radiation. (paper)
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
The Development of Test Facilities for Induced, High-Frequency Plasma Instabilities
We present results from modifications to test facilities equipped with a plasma source capable of producing a LEO-type environment. The modifications impose an oscillation to the output, thus simulating ionospheric disturbance. The frequency of the oscillations is adjustable as well as the base-line output of the source. Test results indicate that the density of the plasma can be varied with minimal impact on other plasma properties such as electron temperature. It is, therefore, possible to simulate realistic plasma environments such as day/night transitions or localized turbulence. The modified source is an effective tool for testing space instruments in a relevant environment increasing the instruments technology readiness level.
McTernan, Jesse K.↗
Stabilization of electron streams in type 3 solar radio bursts
It is shown that the electron streams that give rise to Type 3 solar radio bursts are stable and will not be decelerated while propagating out of the solar corona. The stabilization mechanism depends on the parametric oscillating two stream instability. Radiation is produced near the fundamental and second harmonic of the local electron plasma frequency. Estimates of the emission at the second harmonic indicate that the wave spectra created by the oscillating two stream instability can account for the observed intensities of Type 3 bursts.
Papadopoulos, K.↗