Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on $28.1×10^{6}$ electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from $42.1^{+5.4}_{−5.2}$  GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above $25.2\pm1.8$  GeV. Contrary to the positron flux, which has an exponential energy cutoff of $810^{+310}_{−180}$  GeV, at the 5σ level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons.

We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of $5.4 \times 10^{6}$ nuclei collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the Li/Be flux ratio of $2.0 \pm 0.1$. The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays.

Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from $25.2 \pm 1.8$  GeV compared to the lower-energy, power-law trend, (b) a sharp dropoff above $284^{+91}_{−64} $ GeV, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of $E_{s}=810^{+310}_{−180} $ GeV is established with a significance of more than 4σ. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.

A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on $2.2 \times 10^{6}$ events is presented. The detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. The spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary He, C, and O cosmic rays above ∼700  GV. We observed that the nitrogen flux $Φ_{\rm N}$ can be presented as the sum of its primary component $Φ^{P}_{\rm N}$ and secondary component $Φ^{S}_{\rm N}$, $Φ_{\rm N}=Φ^{P}_{\rm N}+Φ^{S}_{\rm N}$, and we found $Φ_{\rm N}$ is well described by the weighted sum of the oxygen flux $Φ_{\rm O}$ (primary cosmic rays) and the boron flux $Φ_{\rm B}$ (secondary cosmic rays), with $Φ^{P}_{\rm N}=(0.090 \pm 0.002)×Φ_{\rm O}$ and $Φ^{S}_{\rm N}=(0.62 \pm 0.02) \times Φ_{\rm B}$ over the entire rigidity range. This corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few GV to 30% above 1 TV.

We present the precision measurement from May 2011 to May 2017 (79 Bartels rotations) of the proton fluxes at rigidities from 1 to 60 GV and the helium fluxes from 1.9 to 60 GV based on a total of $1\times10^{9}$ events collected with the Alpha Magnetic Spectrometer aboard the International Space Station. This measurement is in solar cycle 24, which has the solar maximum in April 2014. We observed that, below 40 GV, the proton flux and the helium flux show nearly identical fine structures in both time and relative amplitude. The amplitudes of the flux structures decrease with increasing rigidity and vanish above 40 GV. The amplitudes of the structures are reduced during the time period, which started one year after solar maximum, when the proton and helium fluxes steadily increase. Above ∼3  GV the p/He flux ratio is time independent. We observed that below ∼3  GV the ratio has a long-term decrease coinciding with the period during which the fluxes start to rise.

We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on $23.5 \times 10^{6}$ events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the $e^{+}/e^{-}$ flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over $830 \pm 30$ days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by $260 \pm 30$ days from 1 to 6 GeV.

We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with $90 \times 10^{6}$ helium, $8.4 \times 10^{6}$ carbon, and $7.0 \times 10^{6}$ oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B/C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B/C spectral index is reported for the first time. The B/C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B/C ratio is well described by a single power law $R^{Δ}$ with index $Δ=−0.333±0.014(fit)±0.005(syst)$, in good agreement with the Kolmogorov theory of turbulence which predicts $Δ=−1/3$ asymptotically.

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of $^3\mathrm{He}$ and $^4\mathrm{He}$ fluxes are presented. The measurements are based on 100 million $^4\mathrm{He}$ nuclei in the rigidity range from 2.1 to 21 GV, and 18 million $^3\mathrm{He}$ from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the $^3\mathrm{He}$ and $^4\mathrm{He}$ fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio is measured for the first time. Below 4 GV, the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio was found to have a significant long-term time dependence. Above 4 GV, the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio was found to be time independent and its rigidity dependence is well described by a single power law ${\propto R^{\Delta}}$ with ${\Delta = -0.294 \pm 0.004}$. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.

We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with $1.8\times10^6$  Ne, $2.2\times10^6$  Mg, and $1.6\times10^6$  Si nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays.

A spectrometer on the International Space Station has measured the energy spectrum of iron—the heaviest cosmic-ray element characterized to date. The cosmic rays constantly bombarding Earth mostly consist of protons and helium nuclei, but they also include ions of heavier elements. By comparing the energy spectra of different cosmic-ray particles, researchers hope to garner information on the processes that forged and accelerated those particles in supernovae and on the interstellar medium through which the particles propagated. Now, the Alpha Magnetic Spectrometer (AMS) Collaboration has measured, with percent-level precision, the spectrum of iron—the heaviest element yet to be accurately characterized.

An instrument on the International Space Station has revealed new information about how the Sun’s magnetic field affects cosmic rays on their way to Earth.

The Alpha Magnetic Spectrometer (AMS) collaboration, a large research group analyzing data collected by a large magnetic spectrometer in space, recently gathered new insight about the properties and composition of specific types of cosmic rays. In a new paper, published in Physical Review Letters (PRL), they specifically unveiled the composition of primary cosmic-ray carbon, neon, and magnesium, along with the composition and properties of cosmic-ray sulfur.