A5064049799- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Magnetic confinement fusion research
- Geomagnetism and Paleomagnetism Studies
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Plasma Diagnostics and Applications
- Fluid Dynamics and Turbulent Flows
- Advanced Thermodynamics and Statistical Mechanics
- Magnetic Field Sensors Techniques
- Radiative Heat Transfer Studies
- Computer Graphics and Visualization Techniques
- Quantum, superfluid, helium dynamics
- Electromagnetic Launch and Propulsion Technology
- Radiation Therapy and Dosimetry
- Particle accelerators and beam dynamics
- Solar Radiation and Photovoltaics
Los Alamos National Laboratory
2021-2023
University of Alabama in Huntsville
2017-2020
New Mexico Consortium
2018
Abstract The possibility that charged particles are accelerated statistically in a “sea” of small-scale interacting magnetic flux ropes the supersonic solar wind is gaining credence. In this Letter, we extend Zank et al. statistical transport theory for nearly isotopic particle distribution by including an escape term corresponding to loss from finite acceleration region. Steady-state 1D solutions both velocity function and differential intensity derived. We show Ulysses observations...
Abstract An observational analysis of an atypical energetic particle event near 5 au measured by the Ulysses spacecraft is presented. A previous study has attributed unusual enhancement proton flux to presence small-scale dynamic magnetic islands or ropes. Here, we find that generation these may be related interaction a stream region (SIR) and heliospheric current sheet (HCS). Particles are accelerated trapped within SIR structure characterized forward shock–reverse wave pair. Analysis...
We study the existence and property of Fast magnetosonic modes in 3D compressible MHD turbulence by carrying out a number simulations with incompressible driving conditions. use two approaches to determine presence modes: mode decomposition based on spatial variations only spatio-temporal 4D-FFT analysis all fluctuations. The latter method enables us quantify fluctuations that satisfy dispersion relation finite frequency. Overall, we find fraction identified via 4D FFT approach total...
Abstract Voyager 1 observed compressible magnetic turbulence in the very local interstellar medium (VLISM). We show that inner heliosheath (IHS) fast- and slow-mode waves incident on heliopause (HP) generate VLISM fast-mode only propagate into VLISM. suggest this is origin of transmitted across a tangential discontinuity such as HP are strongly refracted crossing subsequently at highly oblique angles to field. Thus, contribute primarily not transverse components fluctuating field variance...
It is well known that collisionless systems are dissipation free from the perspective of particle collision and thus conserve entropy. However, processes such as magnetic reconnection turbulence appear to convert large-scale energy into heat. In this paper, we investigate energization heating plasma. The process discussed in terms fluid entropy both isotropic gyrotropic forms. Evolution equations for derived they reveal mechanisms lead changes These verified by a particle-in-cell simulation...
Abstract With the onset of solar maximum and expected increased prevalence interplanetary shock waves, Parker Solar Probe is likely to observe numerous shocks in next few years. An outstanding question that has received surprisingly little attention been how turbulence interacts with collisionless waves. Turbulence supersonic wind described frequently as a superposition majority 2D minority slab component. We formulate collisional perpendicular shock-turbulence transmission problem way...
Abstract The evolution of the velocity distribution pickup ions is crucial for understanding energetic neutral atom (ENA) fluxes observed by Interstellar Boundary Explorer. Pickup in heliosheath contain two main components: those transmitted across heliospheric termination shock and locally created within heliosheath. In this work, we discuss latter component. We find that charge exchange solar wind (NSW) may be a significant source ENA between about 100 eV 1 keV. Moreover, newborn can...
Abstract Many questions remain about the compressibility of solar wind turbulence with respect to its origins and properties. Low plasma beta (ratio thermal magnetic pressure) environments allow for easier generation compressible turbulence, enabling study relationship between density fluctuations turbulent Mach number. Utilizing Parker Solar Probe data, we examine normalized proton <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo...
Most stars generate winds and move through the interstellar medium that surrounds them. This movement creates a cocoon formed by deflection of these envelops protects stars. We call “cocoons” astrospheres. The Sun has its own cocoon, heliosphere. heliosphere is an immense shield Solar System from harsh, galactic radiation. radiation enters affects life on Earth as well human space exploration. Galactic cosmic rays are dominant source principal hazard affecting missions within our System....
Magnetic flux ropes are commonly observed throughout the heliosphere, and recent studies suggest that interacting associated with some energetic particle events. In this work, we carry out 2D particle-in-cell (PIC) simulations to study coalescence of two magnetic (or islands), subsequent plasma energization processes. The initialized islands embedded in a reconnecting current sheet. collide eventually merge into single island. Particles accelerated during process as energy is released...
The solar wind is a magnetized and turbulent plasma. Its turbulence often dominated by Alfv\'enic fluctuations deemed as nearly incompressible far away from the Sun, shown in-situ measurements near 1AU. However, for closer to plasma $\beta$ decreases (often lower than unity) while Mach number $M_t$ increases (can approach unity, e.g., transonic fluctuations). These conditions could produce significantly more compressible effects, characterized enhanced density fluctuations, seen several...
Abstract The distribution of ions in the heliosheath—the region between heliospheric termination shock and heliopause—is important for understanding remote observations energetic neutral atoms (ENAs). ion distributions were estimated previously based on hybrid simulations heating evolution solar wind interstellar pickup across shock, but these estimates only provide near shock. In this work, we use self-consistent kinetic to investigate effects turbulence heliosheath. are compared against...
Solar wind turbulence is often perceived as weakly compressible and the density fluctuations remain poorly understood both theoretically observationally. Compressible magnetohydrodynamic simulations provide useful insights into nature of fluctuations. We discuss a few important effects related to 3D in-situ observations. The observed quantities such power spectrum variance depend on angle between sampling trajectory mean magnetic field due anisotropy turbulence. effect stronger at smaller...
Abstract We present a spatial filtering (or coarse-graining) analysis on 3D magnetized magnetohydrodynamic (MHD) turbulence simulations. The filtered compressible MHD formulae show transfer of kinetic and magnetic energies from large to small scales, as well energy conversion between kinetic, magnetic, thermal energies. anisotropic enables separate analyses the flows perpendicular parallel global mean field. Anisotropy in cascade is demonstrated by larger rate also wavenumbers associated...
Abstract The mechanisms and pathways of magnetic energy conversion are an important subject for many laboratory, space, astrophysical systems. Here, we present a perspective on in magnetohydrodynamics through field curvature relaxation (CR) perpendicular expansion (PE) due to pressure gradients, quantify their relative importance two representative cases, namely 3D reconnection kink-driven instability jet. We find that the CR PE processes have different temporal spatial evolutions these...
Magnetic flux ropes (or magnetic islands) are ubiquitous space plasma structures. Recent observations suggest that they often associated with the acceleration of charged particles, but detailed mechanisms remain unclear. In this study, we present PIC simulations studying particle due to ropes. We consider a simple 2D configuration two-magnetic-island coalescence. Some electrons and protons found be accelerated more than 10 times their initial kinetic energies at end simulation. use tracing...
We perform 2.5D particle-in-cell simulations of decaying turbulence in the presence a guide (out-of-plane) background magnetic field. The fluctuating field initially consists Fourier modes at low wavenumbers (long wavelengths). With time, electromagnetic energy is converted to plasma kinetic (bulk flow+thermal energy) rate per unit volume ${\pp J}\cdot{\pp E}$ for current density J}$ and electric E}$. Such well known evolve toward state with strongly intermittent current. Here we decompose...
Solar wind turbulence is often perceived as weakly compressible and the density fluctuations remain poorly understood both theoretically observationally. Compressible magnetohydrodynamic simulations provide useful insights into nature of fluctuations. We discuss a few important effects related to 3D in-situ observations. The observed quantities such power spectrum variance depend on angle between sampling trajectory mean magnetic field due anisotropy turbulence. effect stronger at smaller...
Many questions remain about the compressibility of solar wind turbulence with respect to its origins and properties. Low plasma beta (ratio thermal magnetic pressure) environments allow for easier generation compressible turbulence, enabling study relationship between density fluctuations turbulent Mach number. Utilizing Parker Solar Probe data, we examine normalized proton $\langle δn_p^2 \rangle ^{1/2}/\langle n_p\rangle = δ{n_p}_{rms}/\langle n_p\rangle$ as a function number $M_t$...