Gamma-Ray Bursts

We consider particle acceleration at the scatter-free limit in quasi-planar shock waves propagating in inhomogeneous magnetic fields. It is shown that both non-constant magnetic field intensity and field-line curvature may lead to efficient acceleration of particles at shocks propagating through the structure. Shocks propagating towards increasing magnetic field intensity trap energetic particles, and as the field increases at the shock front the particles, by conserving their magnetic moment µB = E⊥/B, increase their perpendicular energy by the ratio of maximum field magnitude to the field magnitude at the point of injection, E⊥,max = E⊥,injBmax/Binj .T his may result in energy gains by factor of 100 in the solar corona. In addition, shocks propagating in curved magnetic fields may trap particles and accelerate them to high energies on field lines on which the shock-normal angle gradually increases toward 90 ◦ . Suitable fieldline geometries should be common in many astrophysical objects, such as stellar coronae and quasi-perpendicular parts of supernova shocks.

Particle Acceleration at Shocks Propagating in Inhomogenous Magnetic Fields

\n Scatter-free acceleration is investigated for a test particle thrusted by a moving magnetized cloud in the presence of the uniform interstellar magnetic field. It is found that depending on the orientation of the background magnetic field, three different scenarios occur for the interacting particle. In some cases, the particle reflects into space with a negligible increase in energy. Otherwise, the particle is either trapped at the wavefront or is injected inside the cloud. The trapped particle moves with the cloud and gains energy through the magnetic trapping acceleration mechanism, which is already investigated in previous reports. The injected particle accelerates through a different mechanism, which is introduced in this paper as the spiral acceleration. In this mechanism, the particle moves in a spiral path and gains energy by the convective electric field of the cloud. The radius of the spiral increases as the particle gains more energy and the process continues until the particle is located inside the cloud. Since in most cases the trapping condition is not satisfied, the spiral acceleration mechanism is of great importance.

Scatter-free acceleration of particles by interaction with plasma shock waves in the interstellar medium

We discuss magnetic field generation by the proton Weibel instability in relativistic shocks, a situation that applies to the external shocks in the fireball model for Gamma-ray Bursts, and possibly also to internal shocks. Our analytical estimates show that the linear phase of the instability ends well before it has converted a significant fraction of the energy in the proton beam into magnetic energy: the conversion efficiency is much smaller (of order m_e/m_p) in electron-proton plasmas than in pair plasmas. We find this estimate by modelling the plasma in the shock transition zone with a waterbag momentum distribution for the protons and with a background of hot electrons. 
For ultra-relativistic shocks we find that the wavelength of the most efficient mode for magnetic field generation equals the electron skin depth, that the relevant nonlinear stabilization mechanism is magnetic trapping, and that the presence of the hot electrons limits the typical magnetic field strength generated by this mode so that it does not depend on the energy content of the protons. We conclude that other processes than the linear Weibel instability must convert the free energy of the protons into magnetic fields.

/pdf/magnetic-field-generation-in-relativistic-shocks-an-early-2xm2d953op.pdf

Magnetic field generation in relativistic shocks - An early end of the exponential Weibel instability in electron-proton plasmas


 Particle acceleration by plasma shock waves is investigated for a magnetized plasma cloud propagating in a non-uniform background magnetic field by means of analytical and numerical calculations. The mechanism studied here is mainly, magnetic trapping acceleration (MTA) which is previously investigated for a cloud moving through the uniform interstellar magnetic field (IMF). In this work, the acceleration is studied for a cloud moving in an antiparallel background field with spatial variations along the direction of motion. For negative variation, the cloud moves towards an antiparallel magnetic field with an increasing intensity, the trapped particle moves to locations with higher convective electric field and therefore gains more energy over time. For positive variation, the background field decreases to zero and changes into a parallel field with an increasing intensity. It is concluded that, when the background field vanishes, the MTA mechanism ceases and the particle escapes into the space. This leads to a bouncing acceleration which further increases energy of the gyrating particle. The two processes are followed by a shock drift acceleration, where due to the background magnetic field gradient, the particle drifts along the electric field and gains energy. Although for positive variation, three different mechanisms are involved, energy gain is less than in the case of a uniform background field.

Particle acceleration by interstellar plasma shock waves in non-uniform background magnetic field

Control of ordinary and extraordinary waves excitation by an axial magnetic field in motional plasma

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

P Rashed-Mohassel

Author Tools

Chat about Author

Papers

Particle acceleration by interstellar plasma shock waves in non-uniform background magnetic field

Scatter-free acceleration of particles by interaction with plasma shock waves in the interstellar medium

Control of ordinary and extraordinary waves excitation by an axial magnetic field in motional plasma