Researchers Publish Project on How High Energy Electrons Strengthen Magnetic Fields

August 16, 2021 by Darshil Patel

Researchers discovered a way to amplify magnetic fields by high-energy electrons, which can explain high-energy cosmic events and can lead to the development of compact high-energy radiation sources for laboratories.

Electricity and magnetism are related and are now known to be two components of the unified field of electromagnetism. Electrical charges interact by an electric force, and their motion produces a magnetic field. Not only does the charged particle create magnetic fields, but they can also respond to them. In radio waves, electric components and magnetic components coexist and sustain one another. But there are high energy events in the universe where magnetic fields have been discovered to amplify due to high-energy charged particles.

Magnetic fields permeate our universe. Most of the energy in the universe exists in the superheated state known as plasma, an ionized gas of free electrons and ions also called the fourth state of matter. The motion of these charged particles produces magnetic fields which control a wide range of astrophysical phenomena. It has been discovered that these magnetic fields can be amplified by high-energy charged particles and can produce high-energy radiations like gamma-ray bursts. But how these high-energy charged particles affect the magnetic field and how the magnetic field amplifies was not well understood.

In a paper published in Physical Review Letters, researchers from the Department of Energy's SLAC National Accelerator Laboratory have shown how electrons can amplify magnetic fields to much higher intensities.

The motion of electrons carries an electrical current and produces a magnetic field. However, changes from the surrounding plasma interfere with this current and cancel it. This interference makes strong magnetic fields difficult to produce. The researchers, through simulations and theoretical models, discovered that high-energy electrons could emit plasma to create a hole, making it harder for the background plasma to interfere and cancel their current.

The researchers report that a new secondary nonlinear instability grows due to the transverse magnetic pressure produced by a beam of high-energy charged particles. The background ions cannot neutralize this growth easily, and as a result, the magnetic field amplifies, and beam kinetic energy efficiently gets converted into magnetic energy. The researchers show that the magnetic fields can get amplified by orders of magnitude.

3D simulation results of a dilute, ultrarelativistic electron beam propagating through an electron-ion background. Image Courtesy of SLAC National Accelerator Laboratory.


Ryan Peterson, a PhD student at Stanford University and SLAC who is the first author of the publication, explains that as the current is exposed, the strong magnetic fields push the background plasma away, creating even more current to expose, and as a result, produce stronger magnetic fields. He added that these magnetic fields eventually become so strong that they bend electrons and slow them down.

The study of magnetic field amplification can not only help us understand the extreme astrophysical environments but can also aid in laboratories with intense lasers and electron beams. High energy lasers and electron beams are applicable in high-energy accelerators, the biomedical field for targeting tumors precisely, and in microscopic imaging methods, including scanning electron microscope (SEM), electron diffraction (ED), and high-resolution transmission electron microscopy (HRTEM).

"Every time a new fundamental process is identified, it can have important consequences and applications in different areas of research," says Frederico Fiuza, a scientist who worked on this research and leads the high energy density science theory group at SLAC. "In this case, the amplification of magnetic fields by high-energy electrons is known to be important not only for extreme astrophysical environments, such as the gamma-ray bursts but also for laboratory applications based on electron beams."

The researchers are currently working on simulations to understand how these processes play a role in gamma-ray bursts. Furthermore, they are also finding ways to reproduce it in laboratory experiments as compact high-energy radiation sources, which would allow scientists to take pictures of matter on the atomic scale with extremely high resolution for applications in medicine, biology, and materials research.