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Antiprotons and Elementary Particles over a Solar Cycle: Results from the Alpha Magnetic Spectrometer
M Aguilar1, G Ambrosi2, H Anderson3
1Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), 28040 Madrid, Spain.
Physical Review Letters
|February 21, 2025
Summary
Cosmic antiproton (p[over ¯]) flux variations are smaller than other cosmic rays over an 11-year solar cycle. A universal relation exists between rigidity spectrum shape and flux variation magnitude for all charged particles.
Area of Science:
- Cosmic ray physics
- Heliophysics
- Astrophysics
Background:
- Cosmic rays, including protons (p), electrons (e^{-}), and positrons (e^{+}), exhibit significant temporal variations over the 11-year solar cycle.
- Antiprotons (p[over ¯]) are secondary cosmic ray particles whose flux variations provide insights into solar modulation processes.
Purpose of the Study:
- To analyze the behavior of cosmic antiproton fluxes over an 11-year solar cycle.
- To compare the temporal variations of antiprotons with those of protons, electrons, and positrons.
- To investigate the relationship between spectral shape and flux variation magnitude for different charged particles.
Main Methods:
- Analysis of 1.1×10^{6} cosmic antiproton events.
- Study of data spanning an 11-year solar cycle.
- Model-independent analysis of rigidity spectra and flux temporal variations.
Main Results:
- Antiproton flux temporal variation magnitude is significantly smaller than that of protons, electrons, and positrons.
- Hysteresis observed between antiproton and proton fluxes.
- Linear correlation found between antiproton and electron fluxes.
- Universal relation identified between rigidity spectrum shape and flux temporal variation magnitude for both positive and negative charged particles.
Conclusions:
- Antiprotons exhibit distinct modulation properties compared to other cosmic rays.
- The observed relationships provide crucial data for understanding particle transport in the heliosphere.
- Simultaneous measurements of various charged particles offer unique insights into solar modulation mechanisms.
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