scholarly journals Mildly relativistic magnetized shocks in electron–ion plasmas – II. Particle acceleration and heating

2021 ◽  
Author(s):  
Arianna Ligorini ◽  
Jacek Niemiec ◽  
Oleh Kobzar ◽  
Masanori Iwamoto ◽  
Artem Bohdan ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Energy Transfer ◽  
High Resolution ◽  
Power Law ◽  
Thermal Power ◽  
Two Dimensional ◽  
Particle In Cell ◽  
Electron Spectra ◽  
Wakefield Acceleration ◽  
Ion Plasma

Abstract Particle acceleration and heating at mildly relativistic magnetized shocks in electron-ion plasma are investigated with unprecedentedly high-resolution two-dimensional particle-in-cell simulations that include ion-scale shock rippling. Electrons are super-adiabatically heated at the shock, and most of the energy transfer from protons to electrons takes place at or downstream of the shock. We are the first to demonstrate that shock rippling is crucial for the energization of electrons at the shock. They remain well below equipartition with the protons. The downstream electron spectra are approximately thermal with a limited supra-thermal power-law component. Our results are discussed in the context of wakefield acceleration and the modelling of electromagnetic radiation from blazar cores.

scholarly journals Kinetic simulations of mildly relativistic shocks – I. Particle acceleration in high Mach number shocks

2019 ◽  
Vol 485 (4) ◽  
pp. 5105-5119 ◽  
Author(s):  
P Crumley ◽  
D Caprioli ◽  
S Markoff ◽  
A Spitkovsky
Keyword(s):  
Particle Acceleration ◽  
Mach Number ◽  
Magnetic Fields ◽  
Thermal Power ◽  
Power Laws ◽  
Maximum Energy ◽  
Magnetic Fluctuations ◽  
Energy Fraction ◽  
Particle In Cell ◽  
Relativistic Shocks

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 a Mach number of 15. We examine both subluminal (quasi-parallel) and superluminal (quasi-perpendicular) magnetic field orientations. We find that quasi-parallel shocks are mediated by a filamentary non-resonant (Bell) instability driven by returning ions, producing magnetic fluctuations on scales comparable to the ion gyroradius. In quasi-parallel shocks, both electrons and ions are accelerated into non-thermal power laws whose maximum energy grows linearly with time. The upstream heating of electrons is small, and the two species enter the shock front in rough thermal equilibrium. The shock’s structure is complex; the current of returning non-thermal ions evacuates cavities in the upstream that form filaments of amplified magnetic fields once advected downstream. At late times, 10 per cent of the shock’s energy goes into non-thermal protons and ${\gtrsim }10{{\ \rm per\ cent}}$ into magnetic fields. We find that properly capturing the magnetic turbulence driven by the non-thermal ions is important for properly measuring the energy fraction of non-thermal electrons, εe. We find εe ∼ 5 × 10−4 for quasi-parallel shocks with v = 0.75c, slightly larger than what was measured in simulations of non-relativistic shocks. In quasi-perpendicular shocks, no non-thermal power-law develops in ions or electrons. The ion acceleration efficiency in quasi-parallel shocks suggests that astrophysical objects that could host mildly relativistic quasi-parallel shocks – for example, the jets of active galactic nuclei or microquasars – may be important sources of cosmic rays and their secondaries, such as gamma-rays and neutrinos.

scholarly journals Particle acceleration in relativistic magnetic flux-merging events

2017 ◽  
Vol 83 (6) ◽  
Author(s):  
Maxim Lyutikov ◽  
Lorenzo Sironi ◽  
Serguei S. Komissarov ◽  
Oliver Porth
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Magnetic Flux ◽  
Power Law ◽  
Magnetic Energy ◽  
Thermal Power ◽  
Local Magnetic Field ◽  
Flux Tubes ◽  
Maximal Energy ◽  
Magnetic Flux Tubes

Using analytical and numerical methods (fluid and particle-in-cell simulations) we study a number of model problems involving merger of magnetic flux tubes in relativistic magnetically dominated plasma. Mergers of current-carrying flux tubes (exemplified by the two-dimensional ‘ABC’ structures) and zero-total-current magnetic flux tubes are considered. In all cases regimes of spontaneous and driven evolution are investigated. We identify two stages of particle acceleration during flux mergers: (i) fast explosive prompt X-point collapse and (ii) ensuing island merger. The fastest acceleration occurs during the initial catastrophic X-point collapse, with the reconnection electric field of the order of the magnetic field. During the X-point collapse, particles are accelerated by charge-starved electric fields, which can reach (and even exceed) values of the local magnetic field. The explosive stage of reconnection produces non-thermal power-law tails with slopes that depend on the average magnetization $\unicode[STIX]{x1D70E}$. For plasma magnetization $\unicode[STIX]{x1D70E}\leqslant 10^{2}$ the spectrum power-law index is $p>2$; in this case the maximal energy depends linearly on the size of the reconnecting islands. For higher magnetization, $\unicode[STIX]{x1D70E}\geqslant 10^{2}$, the spectra are hard, $p<2$, yet the maximal energy $\unicode[STIX]{x1D6FE}_{\text{max}}$ can still exceed the average magnetic energy per particle, ${\sim}\unicode[STIX]{x1D70E}$, by orders of magnitude (if $p$ is not too close to unity). The X-point collapse stage is followed by magnetic island merger that dissipates a large fraction of the initial magnetic energy in a regime of forced magnetic reconnection, further accelerating the particles, but proceeds at a slower reconnection rate.

scholarly journals Particle acceleration by relativistic expansion of magnetic arcades

2006 ◽  
Vol 2 (14) ◽  
pp. 102-102
Author(s):  
Hiroyuki Takahashi ◽  
Eiji Asano ◽  
Ryoji Matsumoto
Keyword(s):  
Particle Acceleration ◽  
Energy Spectrum ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Power Law ◽  
Magnetic Energy ◽  
Particle In Cell ◽  
A Current

AbstractWe carried out relativistic force free simulations and Particle In Cell (PIC) simulations of twist injection into the magnetic arcades emerging on the surface of a magnetar. As the magnetic energy is accumulated in the arcades, they expand self-similarly. In the arcades, a current sheet is formed and magnetic reconnection takes place. We also carried out 2-dimensional PIC simulations for the study of particle acceleration through magnetic reconnection. As a result, the energy spectrum of particles can be fitted by a power-law.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

High resolution two-dimensional motility mapping; Methodology and initial results

2001 ◽  
Vol 120 (5) ◽  
pp. A226-A226 ◽  
Author(s):  
W LAMMERS ◽  
S DHANASEKARAN ◽  
J SLACK ◽  
B STEPHEN
Keyword(s):  
High Resolution ◽  
Two Dimensional ◽  
Initial Results

Diversity of Glycoprotein Deficiencies in Glanzmann’s Thrombasthenia

1985 ◽  
Vol 54 (03) ◽  
pp. 626-629 ◽  
Author(s):  
M Meyer ◽  
F H Herrmann
Keyword(s):  
High Resolution ◽  
Gel Electrophoresis ◽  
Type Ii ◽  
Two Dimensional ◽  
Two Dimensional Gel Electrophoresis ◽  
Structural Variant ◽  
Glanzmann’S Thrombasthenia ◽  
Crossed Immunoelectrophoresis ◽  
Glanzmann's Thrombasthenia ◽  
Platelet Proteins

SummaryThe platelet proteins of 9 thrombasthenic patients from 7 families were analysed by high resolution two-dimensional gel electrophoresis (HR-2DE) and crossed immunoelectrophoresis (CIE). In 7 patients both glycoproteins (GPs) IIb and Ilia were absent or reduced to roughly the same extent. In two related patients only a trace of GP Ilb-IIIa complex was detected in CIE, but HR-2DE revealed a glycopeptide in the position of GP Ilia in an amount comparable to type II thrombasthenia. This GP Ilia-like component was neither recognized normally by anti-GP Ilb-IIIa antibodies nor labeled by surface iodination. In unreduced-reduced two-dimensional gel electrophoresis two components were observed in the region of GP Ilia. The assumption of a structural variant of GP Ilia in the two related patients is discussed.

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