Scientists have discovered a new instability in plasma, revolutionizing our understanding of cosmic rays. This groundbreaking discovery reveals that cosmic rays generate electromagnetic waves within plasma and influence their paths. This collective behavior of cosmic rays, similar to waves formed by water molecules, challenges previous theories and holds promise for insights into intragalactic cosmic ray transport and its role in galaxy evolution. Credit: SciTechDaily.com
Scientists at the Potsdam Leibniz Institute for Astrophysics (AIP) have discovered a new substance. plasma This instability is expected to revolutionize our understanding of the origin of cosmic rays and their dynamic impact on galaxies.
At the beginning of the last century, Victor Hess discovered a new phenomenon called cosmic rays, for which he was later awarded the Nobel Prize. He conducted high-altitude balloon flights and discovered that the Earth’s atmosphere was not ionized by ground radiation. Instead, he confirmed that the origin of ionization was extraterrestrial. Later, it was discovered that cosmic “rays” are composed of charged particles that travel from space at speeds close to the speed of light. radiation. However, the name “cosmic rays” outlasted these discoveries.
Recent advances in cosmic ray research
In the new study, AIP scientist and lead author of the study, Dr. Mohammad Shalaby, and his collaborators performed numerical simulations to trace the trajectories of many cosmic ray particles, showing that these particles We studied how the plasma interacts with the surrounding plasma, which is made up of electrons and electrons. proton.
Simulation of cosmic rays flowing in the opposite direction to the background plasma and causing plasma instability. The distribution of background particles in response to streaming cosmic rays is shown in phase space spanned by the particle’s position (horizontal axis) and velocity (vertical axis). Color visualizes number density, and holes in phase space represent the highly dynamic nature of instabilities that break up ordered motion into random motion. Credit: Shalaby/AIP
When researchers studied cosmic rays flying from one side of the simulation to the other, they discovered a new phenomenon that excites electromagnetic waves in the background plasma. These waves exert a force on the cosmic rays, causing them to change their meandering paths.
Understanding cosmic rays as a collective phenomenon
Most importantly, this new phenomenon is best understood if we think of cosmic rays as supporting collective electromagnetic waves rather than acting as individual particles. When these waves interact with the background fundamental waves, they are strongly amplified and a transfer of energy occurs.
“This insight allows us to think of cosmic rays in this context as behaving more like radiation than individual particles, as Victor Hess originally believed,” said AIP Cosmology and High Energy Astrophysics. says Professor Christoph Pfrommer, head of the section. .
Momentum distribution of protons (dashed lines) and electrons (solid lines). The appearance of a high-energy electron tail in a slowly moving shock is shown. This is the result of interactions with electromagnetic waves caused by newly discovered plasma instabilities (red) that are absent from faster shocks (black). This shows the importance of understanding the physics of the acceleration process, since only high-energy electrons produce observable radio radiation. Credit: Shalaby/AIP
A good analogy for this behavior is that individual water molecules come together to form waves that break on the shore. “This progress was only made possible by taking into account smaller scales, which had been overlooked until now and called into question the use of effective fluid dynamics theory when studying plasma processes,” explains Dr. Mohammad Shalaby. To do.
Meaning and application
This newly discovered plasma instability has many applications, including the first study of how electrons from thermal interstellar plasma are accelerated to high energies in supernova remnants. It also includes an explanation.
“This newly discovered plasma instability represents a major advance in our understanding of acceleration processes and finally explains why these supernova remnants glow in radio waves and gamma rays.” Mohammad Shalaby reports.
Moreover, this breakthrough opens the door to a deeper understanding of the fundamental processes of cosmic ray transport in galaxies. This represents the biggest mystery in understanding the processes that form galaxies during the evolution of the universe.
References:
“Deciphering the physical basis of mesoscale instability” by Mohammad Shalaby, Timon Thomas, Christoph Pfrommer, Reuven Lemmerz, and Virginia Bresci, December 12, 2023, Plasma Physics Journal.
DOI: 10.1017/S0022377823001289
“Mechanism of efficient electron acceleration in parallel non-relativistic shocks” by Mohammad Shalaby, Reuven Lemmerz, Timon Thomas, and Christoph Pfromer, May 4, 2022, Astrophysics > High-energy astrophysical phenomena.
arXiv:2202.05288
“New Cosmic Ray Instabilities” by Mohammad Shalaby, Timon Thomas, and Christoph Pfrommer, February 24, 2021, of astrophysical journal.
DOI: 10.3847/1538-4357/abd02d
Source: scitechdaily.com
