A5090347903- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Laser-Plasma Interactions and Diagnostics
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Magnetic confinement fusion research
- Geomagnetism and Paleomagnetism Studies
- Earthquake Detection and Analysis
- Gas Dynamics and Kinetic Theory
- Astrophysics and Star Formation Studies
- Pulsars and Gravitational Waves Research
- Atomic and Subatomic Physics Research
- Computational Fluid Dynamics and Aerodynamics
- Plasma and Flow Control in Aerodynamics
- Computational Physics and Python Applications
- Atomic and Molecular Physics
- Geophysics and Gravity Measurements
- Particle Detector Development and Performance
Fermi National Accelerator Laboratory
2021-2025
University of Chicago
2016-2025
Princeton University
2012-2023
Max Planck Institute for Nuclear Physics
2023
University of Hawaii System
2021-2023
Gran Sasso Science Institute
2021-2023
University of Illinois Chicago
2023
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso
2021-2023
University of Hawaiʻi at Mānoa
2021
Institute for the Science and Technology of Plasmas
2021
We use two-dimensional and three-dimensional hybrid (kinetic ions–fluid electrons) simulations to investigate particle acceleration magnetic field amplification at non-relativistic astrophysical shocks. show that diffusive shock operates for quasi-parallel configurations (i.e., when the background is almost aligned with normal) and, large sonic Alfvénic Mach numbers, produces universal power-law spectra ∝p−4, where p momentum. The maximum energy of accelerated ions increases time, it only...
We use large hybrid simulations to study ion acceleration and generation of magnetic turbulence due the streaming particles that are self-consistently accelerated at non-relativistic shocks. When is efficient, we find upstream field significantly amplified. The total amplification factor larger than 10 for shocks with Alfvénic Mach number M = 100, scales square root M. spectral energy density excited determined by distribution particles, moderately strong (M ≲ 30) agrees well prediction...
We study diffusive shock acceleration (DSA) of protons and electrons at nonrelativistic, high Mach number, quasiparallel, collisionless shocks by means self-consistent 1D particle-in-cell simulations. For the first time, both species are found to develop power-law distributions with universal spectral index $\ensuremath{-}4$ in momentum space, agreement prediction DSA. find that scattering is mediated right-handed circularly polarized waves excited current energetic via nonresonant hybrid...
Very recent gamma-ray observations of G120.1+1.4 (Tycho's) supernova remnant (SNR) by Fermi-LAT and VERITAS provided new fundamental pieces information for understanding particle acceleration non-thermal emission in SNRs. We want to outline a coherent description Tycho's properties terms SNR evolution, shock hydrodynamics multi-wavelength accounting at the forward via first order Fermi mechanism. adopt here quick reliable semi-analytical approach non-linear diffusive which includes magnetic...
A rapidly growing amount of evidences, mostly coming from the recent gamma-ray observations Galactic supernova remnants (SNRs), is seriously challenging our understanding how particles are accelerated at fast shocks. The cosmic-ray (CR) spectra required to account for observed phenomenology in fact as steep $E^{-2.2}--E^{-2.4}$, i.e., steeper than test-particle prediction first-order Fermi acceleration, and significantly what expected a more refined non-linear theory diffusive shock...
We use large hybrid (kinetic protons-fluid electrons) simulations to investigate the transport of energetic particles in self-consistent electromagnetic configurations collisionless shocks. In previous papers this series, we showed that ion acceleration may be very efficient (up $10-20\%$ energy), and outlined how streaming amplifies upstream magnetic field. Here, measure particle diffusion around shocks with different strengths, finding mean free path for pitch-angle scattering ions is...
We formulate a magnetohydrodynamic-particle-in-cell (MHD-PIC) method for describing the interaction between collisionless cosmic ray (CR) particles and thermal plasma. The plasma is treated as fluid, obeying equations of ideal MHD, while CRs are relativistic Lagrangian subject to Lorentz force. Backreaction from gas included in form momentum energy feedback. In addition, we include electromagnetic feedback due CR-induced Hall effect that becomes important when electron–ion drift velocity...
We use kinetic hybrid simulations (kinetic ions - fluid electrons) to characterize the fraction of that are accelerated non-thermal energies at non-relativistic collisionless shocks. investigate properties shock discontinuity and show shocks propagating almost along background magnetic field (quasi-parallel shocks) reform quasi-periodically on ion cyclotron scales. Ions impinge when is steepest specularly reflected. This a necessary condition for being injected, but it not sufficient. Also...
We present X-ray and radio observations of the Fast Blue Optical Transient (FBOT) CRTS-CSS161010 J045834-081803 (CSS161010 hereafter) at t=69-531 days. CSS161010 shows luminous ($L_x\sim5\times 10^{39}\,\rm{erg\,s^{-1}}$) ($L_{\nu}\sim10^{29}\,\rm{erg\,s^{-1}Hz^{-1}}$) emission. The emission peaked ~100 days post transient explosion rapidly decayed. interpret these in context synchrotron from an expanding blastwave. launched a mildly relativistic outflow with velocity $\Gamma\beta c\ge0.55c$...
Abstract We use fully kinetic particle-in-cell simulations with unprecedentedly large transverse box sizes to study particle acceleration in weakly magnetized mildly relativistic shocks travelling at a velocity ≈ 0.75c and Mach number of 15. examine both subluminal (quasi-parallel) superluminal (quasi-perpendicular) magnetic field orientations. find that quasi-parallel are mediated by filamentary non-resonant (Bell) instability driven returning ions, producing fluctuations on scales...
Analysis of 15314 electron velocity distribution functions (VDFs) within $\pm$2 hours 52 interplanetary (IP) shocks observed by the \emph{Wind} spacecraft near 1 AU are introduced. The VDFs fit to sum three model for cold dense core, hot tenuous halo, and field-aligned beam/strahl component. best results were found modeling core as either a bi-kappa or symmetric (or asymmetric) bi-self-similar function, while both halo components function. This is first statistical study show that better...
HelioSwarm (HS) is a NASA Medium-Class Explorer mission of the Heliophysics Division designed to explore dynamic three-dimensional mechanisms controlling physics plasma turbulence, ubiquitous process occurring in heliosphere and plasmas throughout universe. This will be accomplished by making simultaneous measurements at nine spacecraft with separations spanning magnetohydrodynamic sub-ion spatial scales variety near-Earth plasmas. In this paper, we describe scientific background for HS...
Collisionless shock waves, found in supernova remnants, interstellar, stellar, and planetary environments, laboratories, are one of nature's most powerful particle accelerators. This study combines situ satellite measurements with recent theoretical developments to establish a reinforced acceleration model for relativistic electrons. Our incorporates transient structures, wave-particle interactions, variable stellar wind conditions, operating collectively multiscale set processes. We show...
We present a semi-analytical kinetic calculation of the process non-linear diffusive shock acceleration (NLDSA) which includes magnetic field amplification due to cosmic ray induced streaming instability, dynamical reaction amplified and possible effects turbulent heating. The approach is specialized parallel waves parameters we chose are ones appropriate forward shocks in Supernova Remnants. Our allows us show that net effect enhance maximum momentum accelerated particles while reducing...
Stationary solutions to the problem of particle acceleration at shock waves in non-linear regime, when dynamical reaction accelerated particles on cannot be neglected, are known show a prominent energy flux escaping from towards upstream infinity. On physical grounds, escape region has expected all those situations which maximum momentum particles, $p_{max}$, decreases with time, as is case for Sedov-Taylor phase expansion shell Supernova Remnant, both velocity and cosmic ray induced...
A collisionless shock may be strongly modified by the presence of neutral atoms through processes charge exchange between ions and neutrals ionization latter. These two lead to energy momentum charged particles both upstream downstream shock. In particular, that suffer a with shock-heated generate high velocity have finite probability returning upstream. might then deposit heat in plasma exchange, thereby reducing fluid Mach number. consequence this phenomenon, we refer as "neutral return...
Charged particles can be reflected and accelerated by strong (i.e., high Mach number) astrophysical collisionless shock waves, streaming away to form a foreshock region in communication with the shock. Foreshocks are primarily populated suprathermal ions that generate disturbances-large-scale tens thousands of thermal ion Larmor radii), transient (∼5-10 per day) structures. They have recently been found accelerate energies several keV. Although electrons Saturn's number (M>40) bow...
Abstract Diffusive shock acceleration is a prominent mechanism for producing energetic particles in space and astrophysical systems. Such have long been predicted to affect the hydrodynamic structure of shock, turn leading CR spectra flatter than test-particle prediction. However, this work along with companion paper, we use self-consistent hybrid (kinetic ion–fluid electron) simulations show first time how CR-modified shocks actually produce steeper spectra. The steepening driven by...
The Universe is permeated by hot, turbulent, magnetized plasmas. Turbulent plasma a major constituent of active galactic nuclei, supernova remnants, the intergalactic and interstellar medium, solar corona, wind Earth’s magnetosphere, just to mention few examples. Energy dissipation turbulent fluctuations plays key role in heating energization, yet we still do not understand underlying physical mechanisms involved. THOR mission designed answer questions how heated particles accelerated,...
Abstract We study diffusive shock acceleration (DSA) of electrons in nonrelativistic quasi-perpendicular shocks using self-consistent one-dimensional particle-in-cell simulations. By exploring the parameter space sonic and Alfvénic Mach numbers we find that high number can efficiently accelerate to power-law downstream spectra with slopes consistent DSA prediction. Electrons are reflected by magnetic mirroring at drive nonresonant waves upstream. Reflected trapped between front upstream...
Abstract Collisionless plasma shocks are efficient sources of nonthermal particle acceleration in space and astrophysical systems. We use hybrid (kinetic ion—fluid electron) simulations to examine the nonlinear feedback self-generated energetic particles (cosmic rays, CRs) on shock hydrodynamics. When CR is efficient, we find evidence both an upstream precursor, where inflowing compressed heated, a downstream postcursor, energy flux CRs amplified magnetic fields play dynamical role. For...
Abstract Observations of the γ -ray emission around star clusters, isolated supernova remnants, and pulsar wind nebulae indicate that cosmic-ray (CR) diffusion coefficient near acceleration sites can be suppressed by a large factor compared to Galaxy average. We explore effects such local suppression CR on galaxy evolution using simulations disk galaxies with regular high gas fractions. Our results show while propagation constant diffusivity make gaseous disks more stable increasing midplane...
Abstract The nonresonant streaming instability (Bell instability) plays a pivotal role in the acceleration and confinement of cosmic rays (CRs), yet exact mechanism responsible for its saturation magnitude final amplified magnetic field have not been assessed from first principles. Using survey hybrid simulations (with kinetic ions fluid electrons), we study evolution Bell as function parameters CR population. We find that at saturation, pressure is comparable with initial anisotropic...