Cosmic rays make up a plasma of relativistic particles that pervade the galaxy and constitute a considerable fraction of its energy density. Theoretical cosmic-ray research in the Laboratory for High-Energy Astrophysics focuses on the source material out of which the cosmic rays are accelerated, on the mechanisms that accelerate the particles, and on how the particles propagate through the galaxy from their sources to the Earth. A developed Monte Carlo computer code is used to study the acceleration process by plasma shocks, while mathematical models have been designed to describe how charged particles move through randomly disordered magnetic fields. Current research centers on shock acceleration theories and how they may explain the energy spectrum of these high-energy particles. Models of cosmic-ray propagation through the galaxy are also studied to determine how the cosmic-ray beam changes its chemical composition by colliding with the interstellar gas. This helps us to deduce the composition at the acceleration sites so that they can be identified with potential sources such as supernova shock waves. Current research also considers the role of cosmic rays in the origin of the light elements Li, Be, and P. Further work is also in progress to find a better understanding of the cosmic-ray ""knee"", a break in the cosmic ray spectrum at about 3 X 10¹⁵ eV. Such studies are related to the Structure and Evolution of the Universe theme by the study of the transformations of matter and energy as exhibited in the cosmic radiation.

Location:
Goddard Space Flight Center
Greenbelt, Maryland
Field of Science:Astrophysics
Advisors:
Tonia Venters
tonia.m.venters@nasa.gov
301-614-5546

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