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Results for “MAGNETICALLY TRAPPED PARTICLE”

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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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Trapped particle absorption by the Ring of Jupiter

The interaction of trapped radiation with the ring of Jupiter is investigated. Because it is an identical problem, the rings of Saturn and Uranus are also examined. Data from the Pioneer II encounter, deductions for some of the properties of the rings of Jupiter and Saturn. Over a dozen Jupiter magnetic field models are available in a program that integrates the adiabatic invariants to compute B and L. This program is to label our UCSD Pioneer II encounter data with the most satisfactory of these models. The expected effects of absorbing material on the trapped radiation are studied to obtain the loss rate as a function of ring properties. Analysis of the particle diffusion problem rounds out the theoretical end of the ring absorption problem. Other projects include identification of decay products for energetic particle albedo off the rings and moons of Saturn and a search for flux transfer events at the Jovian magnetopause.

Fillius, W.↗
DOE OSTI2026

The Role of Three-dimensional Effects on Ion Injection and Acceleration in Perpendicular Shocks

Understanding the conditions that enable particle acceleration at nonrelativistic collisionless shocks is essential to unveil the origin of cosmic rays. We employ 2D and 3D hybrid simulations (with kinetic ions and fluid electrons) to explore particle acceleration and magnetic field amplification in nonrelativistic perpendicular shocks, focusing on the role of shock drift acceleration and its dependence on the shock Mach number. We perform an analysis of the ion injection process and demonstrate why efficient acceleration is only observed in 3D. In particular, we show that ion injection critically depends on the “porosity” of the magnetic turbulence in the downstream region near the shock, a property describing how easily the postshock region allows particles to traverse it and return upstream without being trapped. This effect can only be properly captured in 3D. Additionally, we explore the impact of numerical resolution on ion energization, highlighting how resolving small-scale turbulence—on scales below the thermal ion gyroradius—is essential for accurately modeling particle injection. Overall, our results emphasize the necessity of high-resolution 3D simulations to capture the fundamental microphysics driving particle acceleration at perpendicular shocks.

Orusa, Luca [Princeton Univ., NJ (United States); ↗
NASA NTRS1978

Stochastic acceleration of solar flare protons

The acceleration of solar flare protons is considered by cyclotron damping of intense Alfven wave turbulence in a magnetic trap. The energy diffusion coefficient is computed for a near-isotropic distribution of super-Alfvenic protons and a steady-state solution for the particle spectrum is found for both transit-time and diffusive losses out of the ends of the trap. The acceleration time to a characteristic energy approximately 20 Mev/nucl can be as short as 10 sec. On the basis of phenomenological arguments an omega/2 frequency dependence for the Alfven wave spectrum is inferred. The correlation time of the turbulence lies in the range .0005 less than tau/corr less than .05s.

Barbosa, D. D.↗
NASA NTRS1994

The population of the magnetosphere by solar winds ions when the interplanetary magnetic field is northward

We have examined some possible entry mechanisms of solar wind ions into the magnetosphere by calculating the trajectories of thousands of non-interacting ions in the magnetic and electric fields from a three dimensional global magnetohydrodynamic (MHD) simulation of the magnetosphere and the magnetosheath, under northward interplanetary magnetic field (IMF) conditions. Particles, launched in the solar wind, entered the magnetosphere and formed the low latitude boundary layer (LLBL), plasma sheet and a region of trapped particles near the Earth. The densities and temperatures we obtained in these regions were realistic, with the exception of trapped particle densities. The dominant entry mechanism was convection into the magnetosphere on reconnecting field lines.

Richard, Robert L.↗
NASA NTRS2001

Detailed numerical simulations of laser cooling processes

We developed a detailed semiclassical numerical code of the forces applied on atoms in optical and magnetic fields to increase the understanding of the different roles that light, atomic collisions, background pressure, and number of particles play in experiments with laser cooled and trapped atoms.

numerical simulations laser cooling processes↗
DOE OSTI2022

Fast nonlinear iterative solver for an implicit, energy-conserving, asymptotic-preserving charged-particle orbit integrator

Here recently, an asymptotic-preserving (AP) particle orbit integrator has been proposed with remarkable properties including exact energy conservation, the ability to capture of all first-order drifts (including the ∇B-drift), the ability to capture trapped-passing boundaries with parallel velocity extremely close to the critical velocity, and the ability to transition from strongly to weakly magnetized spatial regions. The new AP orbit integrator is implicit, employing a Crank-Nicolson (CN) temporal discretization to ensure exact energy conservation. This, in turn, requires a local nonlinear iteration involving particle velocities and positions, and the local electromagnetic fields, to obtain the new-time solution. Ref. [1] did not attempt to provide an efficient solver for this system, and employed a brute-force GMRES-driven Jacobian-free Newton-Krylov (JFNK) solver to invert the particle orbit equations at every timestep for expediency. While JFNK is robust and reliable, it is also expensive and very intrusive for practical implementations of the method (it requires having the JFNK machinery available and solving a 6 x 6 Jacobian system iteratively once per iteration per particle).

97 MATHEMATICS AND COMPUTING↗
NASA NTRSDate not supplied

Inner Magnetospheric Physics

The inner magnetosphere extends from just above the topside ionosphere to approximately 8 RE geocentric distance. Magnetospheric physics is a young science that only started to be recognized as a region with the space observations by Explorer 1 in 1958. The region is mostly populated by ionized gas or plasma from Earth’s ionosphere. Plasma populations are differentiated by their energies primarily. From the least energetic to most are the plasmasphere, ring current, and radiation belts, extending from about 1 eV to 10 MeV in energy and from 1,000s cm-3 down to a few particles per cubic centimeter and less, respectively. The solar wind and solar erupted coronal mass ejections (CMEs) arriving and interacting with Earth’s magnetic field creates a dynamo effect that drives million ampere currents along magnetic field lines that close through the ionosphere. The solar wind dynamo also creates a 100s kV electric field across the magnetosphere that drives convective motion of the plasma within it. The solar wind driven currents compress Earth’s magnetic field on the sunward side and greatly extents the field on the nightside to form the magnetotail. The energy stored in the magnetotail is impulsively released when magnetic field lines there merge, releasing energy into the plasma trapped by the magnetic field. Those plasma become the ring current that loses plasma into the atmosphere to produce the aurora and at the same time ring current plasma can be further energized by wave-particle interactions to become the radiation belts. The presentation will review these topics and a few of the underlying physical processes that are involved in this highly coupled planetary system.

inner magnetosphere↗
DOE OSTI2022

MAGNETIC FIELD MAPPING OF 1.3 GHz SUPERCONDUCTING RADIO FREQUENCY NIOBIUM CAVITIES

Niobium is the material of choice to build superconducting radio frequency (SRF) cavities, which are fundamental building blocks of modern particle accelerators. These cavities require a cryogenic cool-down to ~2 - 4 K for optimum performance minimizing RF losses on the inner cavity surface. However, temperature-independent residual losses in SRF cavities cannot be prevented entirely. One of the significant contributor to residual losses is trapped magnetic flux. The flux trapping mechanism depends on different factors, such as surface preparations and cool-down conditions. We have developed a diagnostic magnetic field scanning system (MFSS) using Hall probes and anisotropic magneto-resistance sensors to study the spatial distribution of trapped flux in 1.3 GHz single-cell cavities. The first result from this newly commissioned system revealed that the trapped flux on the cavity surface might redistribute with increasing RF power. The MFSS was also able to capture significant magnetic field enhancement at specific cavity locations after a quench.

Parajuli, I. P.↗
DOE OSTI2021

Electron dynamics in radio frequency magnetron sputtering argon discharges with a dielectric target

Abstract We demonstrate a self-consistent and complete description of electron dynamics in a typical electropositive radio frequency magnetron sputtering (RFMS) argon discharge with a dielectric target. The electron dynamics, including the electron power absorption dynamics in one radio frequency (RF) period, is studied via a fully kinetic 2d3v particle-in-cell/Monte Carlo collision (PIC/MCC) electrostatic simulation. The interplay between the fundamental plasma parameters is analyzed through their spatiotemporal dynamics. Due to the influence of magnetic trap on the electron transport, a spatially dependent charging that perturbs the electric potential is observed on the dielectric target surface, resulting in a spatially dependent ion energy distribution along the target surface. The E × B drift-to-discharge current ratio is in approximate agreement with Bohm diffusion. The electron power absorption can be primarily decoupled into the positive Ohmic power absorption in the bulk plasma region and the negative pressure-induced power absorption near the target surface. Ohmic power absorption is the dominant electron power absorption mechanism, mostly contributed by the azimuthal electron current. The power absorption due to electron inertial effects is negligible on time-average. Both the maximum power absorption and dissipation of electrons appear in the bulk plasma region during the second half of the RF period, implying a strong electron trapping in magnetron discharges. The contribution of secondary electrons is negligible under typical RFMS discharge conditions.

Physics↗
NASA NTRS1983

Pioneer 11 observations of trapped particle absorption by Amalthea

The discovery of a microsignatury of trapped radiation in the Amalthea orbit as detected by Pioneer 11 in a flyby of Juptier in 1974 is reported and its implications for the radial diffusion coefficient in Jupiter's inner magnetosphere are discussed. A low energy telescope registered the absorption of low-energy protons as a function of the magnetic L shell durig inbound and outbound trajectories. Drift velocities of the 1 MeV particles were calculated. No correspondingly heightened effects were observed from high-energy electrons or heavier nuclei. Further analysis of the 0.5-8.7 MeV protons showed data to be consistent erosion of the particle drift shadows by a diffusion process. A limit was calculated for the highest diffusion coefficient value for the 1 MeV protons at the Amalthea orbit. The results indicate that the diffusion is driven by fluctuating electric or magnetic fields.

Mckibben, R. B.↗
DOE OSTI2021

Shock Propagation and Associated Particle Acceleration in the Presence of Ambient Solar-Wind Turbulence

The topic of this review paper is on the influence of solar wind turbulence on shock propagation and its consequence on the acceleration and transport of energetic particles at shocks. As the interplanetary shocks sweep through the turbulent solar wind, the shock surfaces fluctuate and ripple in a range of different scales. We discuss particle acceleration at rippled shocks in the presence of ambient solar-wind turbulence. This strongly affects particle acceleration and transport of energetic particles (both ions and electrons) at shock fronts. In particular, we point out that the effects of upstream turbulence is critical for understanding the variability of energetic particles at shocks. Moreover, the presence of pre-existing upstream turbulence significantly enhances the trapping near the shock of low-energy charged particles, including those near the thermal energy of the incident plasma, even when the shock propagates normal to the average magnetic field. Pre-existing turbulence, always present in space plasmas, provides a means for the efficient acceleration of low-energy particles and overcoming the well known injection problem at shocks.

, solar wind↗
NASA NTRS1979

Stochastic acceleration of solar flare protons

The acceleration of solar flare protons by the cyclotron damping of intense Alfven wave turbulence in a magnetic trap is considered. The energy diffusion coefficient is computed for a near-isotropic distribution of super-Alfvenic protons, and a steady-state solution for the particle spectrum is found for both transit-time and diffusive losses out of the ends of the trap. The acceleration time to a characteristic energy of about 20 MeV per nucleon can be as short as 10 sec. On the basis of phenomenological arguments, it is inferred that the Alfven wave spectrum typically has an inverse square frequency dependence and that the correlation time of the turbulence lies in the range between 0.5 and 50 msec.

Barbosa, D. D.↗
NASA NTRS1986

Monte Carlo simulation of charged particle impact on the satellites of Jupiter and Saturn

Ensemble-averaged lifetimes of Jovian and Saturnian trapped charged particles against loss by impact on natural satellites are presented. Precise values of these loss rates can be obtained from the known geometry of the satellite orbits, magnetic fields, and particle trajectory. These loss rates are needed as an ingredient of transport theory which is usually formulated in terms of the first and second adiabatic invariants and radial distance. The effects of satellite orbital inclination and eccentricity, ion charge to mass ratio and energy, equatorial pitch, and distance from the planet on the particle lifetime are discussed utilizing a tilted, but not offset, dipolar field geometry resulting in lifetime values expressed as functions of the first two adiabatic invariants and the equatorial radial distance from the planet.

Bell, E. V., II↗
NASA NTRS1990

Particle acceleration by a wave in a strong magnetic field - Regular and stochastic motion

A general theory for the acceleration of a charged particle by a coherent wave of arbitrary polarization, propagation angle, and phase velocity in the presence of a uniform and strong magnetic field is presented. It is shown that the Hamiltonian surfaces are topologically open for waves with parallel phase velocity, equal to or larger than the speed of light. The trapping width is found to be a strong function of the index of refraction (N), and for N = 1 the trapping width increases as a function of the harmonic number. A novel mechanism for coherently accelerating particles to unlimited energies is presented.

Karimabadi, H.↗
NASA NTRS1974

The motion of a proton in the equatorial magnetosphere

A proton of low energy moving in the equatorial plane of the earth will experience drift motions due to both the magnetic field (magnetic gradient drift only, if the field is assumed to be that of a dipole) and the electric field. The electric drift again separates into two parts - the drift due to the main electric field (or convection electric field) existing in the frame of the earth, and that due to the earth's rotation. One result indicated by this work is that at distances of 4 - 6 earth radii, a transition from trapped proton orbits to open trajectories leading to the tail occurs at about 10 kev, the precise value depending upon local time. Such a transition also seems to be indicated by particle observations using Explorer 45. The energy spectrum (at magnetically quiet times) of equatorial protons above this energy can be explained by charge exchange but increased flux observed below it seems to be related to the influx of particles on open orbits from the tail.

Stern, D. P.↗
NASA NTRS1976

The 2- to 12-min quasi-periodic variation of 50- to 1000-keV trapped electron fluxes

It was previously shown that trapped electron fluxes of energies in the range from 50 keV to 1 MeV observed in the afternoon magnetosphere during substorms frequently undergo periodic variations. High-resolution electron spectrometer data indicate that these electron variations are periodic in the range of about 2-12 min, correlated with magnetic field variations, organized by the local magnetic field, and dependent on pitch angle. The observations suggest that the electron variations are adiabatic. The study derives quantitative adiabatic expressions of particle flux variations in a model geomagnetic field perturbation to show that the observational features are consistent with effects arising from adiabatic modulation of trapped particle fluxes.

Lin, C. S.↗