Properties of Heavy Secondary Fluorine Cosmic Rays: Results from the Alpha Magnetic Spectrometer

Area of Science:

• Astrophysics
• Particle Physics
• Cosmic Ray Physics

Background:

• Understanding cosmic ray propagation requires precise knowledge of secondary cosmic ray fluxes and their ratios.
• Secondary cosmic rays provide insights into astrophysical processes and interstellar medium interactions.

Purpose of the Study:

• To investigate the charge and rigidity dependence of heavy secondary cosmic ray fluorine (F).
• To compare the propagation properties of heavy (F, Si) and light (B, O, C) secondary cosmic rays.

Main Methods:

• Analysis of 0.29 million fluorine events using data from the Alpha Magnetic Spectrometer (AMS) on the International Space Station (ISS).
• Measurement of the fluorine flux and the fluorine-to-silicon (F/Si) flux ratio over a rigidity range from 2.15 GV to 2.9 TV.
• Comparison of the rigidity dependence of F/Si with lighter secondary-to-primary ratios like Boron/Oxygen (B/O) or Boron/Carbon (B/C).

Main Results:

• The fluorine energy spectrum deviates from a single power law above 200 GV.
• The rigidity dependence of the heavier F/Si flux ratio differs significantly from the lighter B/O ratio.
• Above 10 GV, the F/Si to B/O ratio follows a power law R^δ with δ = 0.052 ± 0.007.

Conclusions:

• Heavy secondary cosmic rays (e.g., F to Si) exhibit different propagation properties compared to light secondary cosmic rays (e.g., He to O).
• The findings suggest the existence of at least two distinct classes of secondary cosmic rays based on their propagation characteristics.
• This classification has implications for models of cosmic ray origin and transport in the galaxy.