Precision Measurement of Cosmic-Ray Nitrogen and its Primary and Secondary Components with the Alpha Magnetic Spectrometer on the International Space Station

Abstract

A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on 2.2×10^{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_{N} can be presented as the sum of its primary component Φ_{N}^{P} and secondary component Φ_{N}^{S}, Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}, and we found Φ_{N} is well described by the weighted sum of the oxygen flux Φ_{O} (primary cosmic rays) and the boron flux Φ_{B} (secondary cosmic rays), with Φ_{N}^{P}=(0.090±0.002)×Φ_{O} and Φ_{N}^{S}=(0.62±0.02)×Φ_{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.

Deciphering the Local Interstellar Spectra of Secondary Nuclei with the Galprop/Helmod Framework and a Hint for Primary Lithium in Cosmic Rays

“…First, AMS-02 confirmed a clear distinction in the rigidity dependencies between the groups of mostly primary nuclei, He, C, O (Aguilar et al 2017), and secondary nuclei, Li, Be, B (Aguilar et al 2018b), while the nuclei within each group have similar spectra. Nitrogen that is half-primary/halfsecondary fell in between (Aguilar et al 2018c). The spectral index of the primary species, C, O, below/above the break is about α 1 /α 2 ≈2.65/2.55, while for secondary species it is 1 / 2 ≈3.1/2.9.…”

Validation of the Neutron Monitor Yield Function Using Data From AMS‐02 Experiment, 2011–2017

“…This assumption could not be directly verified earlier. Here we can avoid such an ad hoc assumption by using direct measurements of various cosmic ray species spectra made by AMS‐02 (Aguilar et al, ; Aguilar et al, ; Aguilar et al, ). Specifically, we use the measured helium spectra for each BR as an input to the model, assuming that all helium is 4 He.…”

“…Specifically, we use the measured helium spectra for each BR as an input to the model, assuming that all helium is 4 He. Heavier‐than‐helium species were not measured for each BR period, but only time‐integrated spectra are available (Aguilar et al, ; Aguilar et al, ; Aguilar et al, ). However, since the heliospheric modulation of all heavier species is expected to be similar to that of helium, because of the similar charge‐to‐mass ratio, Z i / A i , they can be roughly scaled to each other, namely, their ratio in rigidity is expected to be roughly constant irrespectively of the modulation level, although this might not be exactly correct.…”

Single Molecule Localization Microscopy Analyses of DNA-Repair Foci and Clusters Detected Along Particle Damage Tracks

“…Nitrogen ions were used as they are relevant for both space research and radiotherapy. They are present in galactic and solar cosmic radiation [74] and are extensively produced when cosmic radiation interacts with the atmosphere [75]. Interestingly, Pioneer 10 spacecraft have revealed increased (up to the factor of 20) amounts of N (and O) ions relative to their abundance in galactic or solar cosmic rays, pointing to specific sources of this component of cosmic radiation in the Universe [76].…”