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Home » New plasma instability unveils secrets of cosmic rays and galactic dynamics

New plasma instability unveils secrets of cosmic rays and galactic dynamics

Researchers from the Leibniz Institute for Potsdam (AIP) have unearthed a groundbreaking plasma instability, promising to reshape our comprehension of cosmic ray origins and their dynamic influence on galaxies.

In the early 20th century, Victor Hess's led to the revelation of cosmic rays, earning him the Nobel Prize. His high-altitude balloon flights determined that Earth's atmosphere wasn't ionized by ground radioactivity but by extraterrestrial sources. Despite later confirming that cosmic “rays” comprised charged particles, the term “cosmic rays” persisted.

In their recent research, Dr. Mohamad Shalaby, the study's lead author from AIP, and collaborators employed numerical simulations to trace cosmic ray trajectories and scrutinize interactions with the surrounding plasma of electrons and protons. Published on the arXiv pre-print server, their findings revealed a novel : as cosmic rays traversed the simulation, they induced electromagnetic waves in the plasma, altering their trajectories.

This discovery holds promise for advancing our understanding of cosmic ray dynamics and their intricate interplay with the cosmic .

Distribution of momenta of protons (dashed lines) and electrons (solid lines). Shown is the emergence of the high-energy tail of electrons at a slower moving shock. Credit: Shalaby/AIP

Crucially, comprehending this novel phenomenon hinges on viewing cosmic rays not as independent particles but as supporters of a collective electromagnetic wave. This wave, interacting with background fundamental waves, undergoes substantial amplification, facilitating an energy transfer.

Professor Christoph Pfrommer, leading the and High-Energy Astrophysics section at AIP, underscores, “This insight prompts us to regard cosmic rays akin to radiation, departing from the notion of individual particles, as originally postulated by Victor Hess.” An apt analogy is individual water coalescing to form a wave breaking at the shore.

Dr. Mohamad Shalaby notes, “This progress emerged from scrutinizing smaller scales overlooked before, challenging the applicability of effective hydrodynamic theories in plasma process studies.”

The implications of this plasma instability discovery are far-reaching. It offers an initial explanation for accelerating electrons from thermal interstellar plasma to high energies at supernova remnants.

Shalaby reports, “This newfound plasma instability marks a substantial advance in understanding the acceleration process, elucidating why supernova remnants emit radio and gamma rays.” Moreover, this breakthrough paves the way for a deeper comprehension of the fundamental mechanisms governing cosmic ray transport in galaxies—the paramount enigma in understanding how galaxies evolve during their cosmic journey.

Source: Leibniz Institute for Astrophysics Potsdam

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