Related Experiment Video
Updated: Jun 12, 2026
10:42
Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
A critical Mach number for electron injection in collisionless shocks
Takanobu Amano1, Masahiro Hoshino
1Department of Physics, Nagoya University, Nagoya, 464-8602, Japan. amanot@stelab.nagoya-u.ac.jp
Physical Review Letters
|May 21, 2010
Summary
This study explains how electrons are accelerated in collisionless shocks. An electron beam and whistler waves are key to injecting electrons into the acceleration process, especially in high-speed environments like supernova remnants.
Area of Science:
- Plasma physics
- Astrophysics
- High-energy particle acceleration
Background:
- Collisionless shocks are crucial in astrophysical phenomena.
- Understanding electron acceleration mechanisms is vital for interpreting observations.
Purpose of the Study:
- To investigate electron acceleration in collisionless shocks with arbitrary magnetic field orientations.
- To identify the mechanisms responsible for injecting thermal electrons into diffusive shock acceleration.
Main Methods:
- Analysis of electron beam dynamics and wave excitation.
- Investigation of the shock drift acceleration mechanism.
- Derivation of a critical Mach number for electron injection.
Main Results:
- Electron injection is facilitated by an electron beam with a velocity-space loss cone.
- Whistler waves excited by the electron beam can scatter energetic electrons.
- A critical Alfvén Mach number for electron injection is determined by upstream parameters.
Conclusions:
- The proposed mechanism explains electron injection in collisionless shocks.
- The findings have implications for understanding particle acceleration in supernova remnant shocks.
Related Concept Videos
01:16Shock Waves
While deriving the Doppler formula for the observed frequency of a sound wave, it is assumed that the speed of sound in the medium is greater than the source's speed through it. When this condition is breached, a shock wave occurs.
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
01:19Thomson's e/m Experiment
In a beam of charged particles created by a heated cathode, the particles move at different speeds. However, many applications need a beam with uniform particle speeds. An arrangement known as a velocity selector uses electric and magnetic fields to pick particles with a particular speed from the beam.
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
01:25Multimachine Stability
Multimachine stability analysis is crucial for understanding the dynamics and stability of power systems with multiple synchronous machines. The objective is to solve the swing equations for a network of M machines connected to an N-bus power system.
In analyzing the system, the nodal equations represent the relationship between bus voltages, machine voltages, and machine currents. The nodal equation is given by:
In analyzing the system, the nodal equations represent the relationship between bus voltages, machine voltages, and machine currents. The nodal equation is given by:
01:15Van de Graaff Generator
Van de Graaff generators (or Van de Graaffs) are devices used to demonstrate high voltage due to static electricity that can also be used for research. Robert Van de Graaff first built one in 1931 (based on original suggestions by Lord Kelvin) for use in nuclear physics research.
Van de Graaff uses both smooth and pointed surfaces, conductors, and insulators to generate large static charges and, hence, large voltages. A substantial excess charge can be deposited on the sphere because it moves...
Van de Graaff uses both smooth and pointed surfaces, conductors, and insulators to generate large static charges and, hence, large voltages. A substantial excess charge can be deposited on the sphere because it moves...
01:15Transmission Electron Microscopy
In 1931, physicist Ernst Ruska—building on the idea that magnetic fields can direct an electron beam just as lenses can direct a beam of light in an optical microscope—developed the first prototype of the electron microscope. This development led to the development of the field of electron microscopy. In the transmission electron microscope (TEM), electrons are produced by a hot tungsten element and accelerated by a potential difference in an electron gun, which gives them up to 400 keV in...
01:07Scanning Electron Microscopy
A scanning electron microscope (SEM) is used to study the surface features of a sample by using an electron beam that scans the sample surface in a two-dimensional manner. Typically, areas between ~1 centimeter to 5 micrometers in width can be imaged. SEM can be used to image bacteria, viruses, tissues as well as larger samples like insects. Conventional SEM gives a magnification ranging from 20X to 30,000X and spatial resolution of 50 to 100 nanometers.
Fundamental Principles
Accelerated...
Fundamental Principles
Accelerated...