Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays

Area of Science:

• Astrophysics
• Particle Physics
• Space Science

Background:

• Cosmic rays, composed of charged particles, travel through space and are influenced by solar activity.
• Understanding the behavior of different cosmic ray components, like positrons, electrons, and protons, is crucial for heliospheric physics.

Purpose of the Study:

• To present precision measurements of cosmic positron fluxes over an 11-year solar cycle.
• To compare the time variations of positron fluxes with those of electrons and protons.
• To investigate the charge-sign and mass dependencies of cosmic rays in the heliosphere.

Main Methods:

• Utilized 3.4×10^6 positron events collected by the Alpha Magnetic Spectrometer (AMS) on the International Space Station.
• Analyzed daily cosmic positron fluxes in the rigidity range of 1.00 to 41.9 GV.
• Compared positron flux variations with electron and proton flux data over an 11-year period.

Main Results:

• Positron fluxes exhibit distinct time variations from electron fluxes on both short and long timescales.
• A statistically significant hysteresis ( > 5σ) between electron and positron fluxes was observed below 8.5 GV.
• Positron fluxes show similar time variations to proton fluxes but are modulated more significantly (< 7 GV).

Conclusions:

• Daily positron flux measurements provide unique data for understanding cosmic ray modulation.
• The observed differences in time variation and modulation between cosmic ray components highlight complex heliospheric processes.
• Findings contribute to a deeper understanding of charge-sign and mass dependencies in cosmic ray propagation.