A5064818014- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Nonlinear Waves and Solitons
- Cosmology and Gravitation Theories
- Fluid Dynamics and Turbulent Flows
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Magnetic confinement fusion research
- Dark Matter and Cosmic Phenomena
- Solar Radiation and Photovoltaics
- Nonlinear Photonic Systems
- Gas Dynamics and Kinetic Theory
- Astrophysics and Star Formation Studies
- Quantum chaos and dynamical systems
- Laser-Plasma Interactions and Diagnostics
- Computational Fluid Dynamics and Aerodynamics
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Dust and Plasma Wave Phenomena
- Radiation Therapy and Dosimetry
- Ocean Waves and Remote Sensing
- Quantum, superfluid, helium dynamics
- Black Holes and Theoretical Physics
University of Alabama in Huntsville
2015-2024
Monash University
1976-2024
Ohio University Chillicothe
2016
University of North Texas
2016
University of Arizona
1995-2011
Observatoire de la Côte d’Azur
2010
Centre National de la Recherche Scientifique
2010
University of Alabama
2009
National Space Science and Technology Center
2009
Massachusetts Institute of Technology
2009
The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on Probe Plus is a four sensor instrument suite that provides complete measurements of the electrons ionized helium hydrogen constitute bulk solar wind coronal plasma. SWEAP consists Cup (SPC) Analyzers (SPAN). SPC Faraday looks directly at Sun measures ion electron fluxes flow angles as function energy. SPAN an electrostatic analyzer (ESA) ram side SPP (SPAN-A) ESA anti-ram (SPAN-B). SPAN-A has time flight section enables it...
An emerging paradigm for the dissipation of magnetic turbulence in supersonic solar wind is via localized small-scale reconnection processes, essentially between quasi-2D interacting islands. Charged particles trapped merging islands can be accelerated by electric field generated island and contraction We derive a gyrophase-averaged transport equation experiencing pitch-angle scattering energization super-Alfvénic flowing plasma multiple events. A simpler advection–diffusion nearly isotropic...
A new mechanism for the acceleration of pickup ions by repeated reflections from electrostatic cross shock potential a quasi‐perpendicular is presented. The mechanism, multiply reflected ion (MRI) acceleration, offers resolution to issue injecting into an efficient particle energization scheme, and injection efficiency found be inversely proportional mass charge. By studying energy gain in motional electric field (where steady frame assumed) energized spectrum can computed. Extremely hard...
Shock waves, as shown by simulations and observations, can generate high levels of downstream vortical turbulence, including magnetic islands. We consider a combination diffusive shock acceleration (DSA) magnetic-island-reconnection-related processes an energization mechanism for charged particles. Observations electron ion distributions interplanetary shocks the heliospheric termination (HTS) are frequently inconsistent with predictions classical DSA. utilize recently developed transport...
Numerous problems in space physics and astrophysics require a detailed understanding of the transport dissipation low-frequency turbulence an expanding magnetized flow. We employ scale-separated decomposition incompressible MHD equations (based on Elssässer description) develop moment hierarchy to describe total energy density fluctuations, cross-helicity, difference, correlation lengths corresponding forward- backward-propagating modes difference. The terms for various are derived....
Simulations of particle acceleration in turbulent plasma regions with multiple contracting and merging (reconnecting) magnetic islands emphasize the key role temporary trapping island structures for efficient particles to form hard power-law spectra. Statistical kinetic transport theories have been developed that capture essential physics multi-island regions. The theory Zank et al. is further by considering effects both mean variance electric fields induced dynamics inertial-scale flux...
Increases of ion fluxes in the keV-MeV range are sometimes observed near heliospheric current sheet (HCS) during periods when other sources absent. These resemble solar energetic particle (SEP) events, but events weaker and apparently local. Conventional explanations based on either shock acceleration charged particles or due to magnetic reconnection at interplanetary sheets not persuasive. We suggest instead that recurrent occurs HCS smaller wind (Zharkova & Khabarova 2012), which a...
We explore the role of heliospheric magnetic field configurations and conditions that favor generation confinement small-scale islands associated with atypical energetic particle events (AEPEs) in solar wind. Some AEPEs do not align standard acceleration mechanisms, such as flare-related or simple diffusive shock processes related to interplanetary coronal mass ejections (ICMEs) corotating interaction regions (CIRs). As we have shown recently, flux enhancements may well originate locally can...
The problem of perpendicular diffusion by a particle in turbulent plasma is enduring interest and one that has yet to be fully solved. Analytic models do not agree with either observations or numerical simulations. Recently, nonlinear guiding center theory (NLGC) was developed Matthaeus et al. [2003] which, for the first time, appears consistent simulations both high‐energy low‐energy regimes, provided transverse magnetic field complex. Flux surfaces high complexity are characterized rapid...
A Chapman-Kolmogorov equation description of compound transport cosmic rays due to random walk the magnetic field lines, and for a range models particle along field, is developed. The probability distribution, Pp, propagation corresponds either (1) ballistic or scatter-free model, (2) parallel diffusion (3) telegrapher model. distribution function (pdf) describing statistics, PFRW, assumed be Gaussian. These are used discuss features dropout events in low-energy, solar cosmic-ray intensity...
Whether a magnetic flux rope is pre-existing or formed in situ the Sun's atmosphere, there little doubt that reconnection essential to release during its ejection. During this process, question remains: how does change flux-rope structure? In work, we continue with original study of Qiu et al. by using larger sample flare–coronal mass ejection (CME)–interplanetary CME (ICME) events compare properties ICME/magnetic cloud (MC) ropes measured at 1 AU and associated solar progenitors including...
view Abstract Citations (101) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the drift mechanism for energetic charged particles at shocks Webb, G. M. ; Axford, W. I. Terasawa, T. An adiabatic treatment is applied to analysis of energy changes particles, a plane shock, which are caused by 'drift' mechanism. The indicates that in case fast MHD lose due acceleration magnetic field with velocity being antiparallel electric field. They then...
ABSTRACT Computational and observational evidence is accruing that heliospheric shocks, as emitters of vorticity, can produce downstream magnetic flux ropes filaments. This led Zank et al. to investigate a new paradigm whereby energetic particle acceleration near shocks combination diffusive shock (DSA) with by many small-scale contracting reconnecting (merging) ropes. Using model where flux-rope involves first-order Fermi mechanism due the mean compression numerous ropes, provide...
Abstract Voyager 1 observed Kolmogorov-like ( k −5/3 ) compressible turbulence just upwind of the heliopause. Subsequent measurements by further from heliopause revealed that fluctuations were now fully incompressible, with a spectrum was essentially identical to earlier spectrum. Zank et al. showed only fast magnetosonic modes could be transmitted inner heliosheath into very local interstellar medium (VLISM), and exhibit We show here small plasma beta VLISM admits three-wave interactions...
A time-dependent focused transport approach to modeling diffusive shock acceleration of interstellar pickup ions at the termination is discussed. By taking into account time variations in magnetic field angle, and thus by implication obliquity injection speed using Voyager 1 observations as guide, we show that unaccelerated core protons can be accelerated nearly perpendicular heliospheric nose. Many features anomalous cosmic rays, observed spacecraft energies below big spectral dip starting...
We present a detailed guide to advanced collisionless fluid models that incorporate kinetic effects into the framework, and are much closer description than traditional magnetohydrodynamics. Such directly applicable modelling turbulent evolution of vast array astrophysical plasmas, such as solar corona wind, interstellar medium, well accretion disks galaxy clusters. The text can be viewed Landau it is divided two parts. Part 1 dedicated obtained by closing hierarchy with simple (non-Landau...
Abstract Analytical solutions for 2D and slab turbulence energies in the solar corona are presented, including a derivation of corresponding correlation lengths, with implications proton electron temperatures corona. These derived by solving transport equations their as well pressures. The assume background profiles wind speed, mass density, Alfvén velocity. Our analytical can be related to those obtained from joint Parker Solar Probe Orbiter Metis coronagraph observations, reported Telloni...
view Abstract Citations (82) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Particle Injection and the Structure of Energetic-Particle--modified Shocks Zank, G. P. ; Webb, M. Donohue, D. J. A macroscopic 'self-consistent' nonlinear two-fluid model is developed for energetic-particle-modeled shocks. The incorporates particle exchange between a thermal gas an energetic population via 'thermal leakage' mechanism. In model, injection regarded as...
view Abstract Citations (39) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multidimensional Green's Functions and the Statistics of Diffusive Shock Acceleration Webb, G. M. ; Zank, P. Ko, C. Donohue, D. J. A three-dimensional, time-dependent function for diffusive shock acceleration energetic charged particles at general oblique MHD shocks, without losses, is derived. By interpreting as a probability distribution, various statistical means...
view Abstract Citations (64) References (50) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Diffusion Approximation and Transport Theory for Cosmic Rays in Relativistic Flows Webb, G. M. Equations describing the transport of cosmic rays relativistic flows diffusion approximation are obtained. analysis is based on zeroth, first, second differential moment equations Boltzmann equation with a BGK collision term. A perturbation solution yields both co-moving...