Measurement of the chemical and isotopic composition of cosmic rays is essential for the precise understanding of their propagation in the galaxy. While the model parameters are mainly determined using the B/C ratio, the study of extended sets of ratios can provide stronger constraints on the propagation models. In this paper the relative abundances of the light nuclei lithium, beryllium, boron and carbon are presented. The secondary to primary ratios Li/C, Be/C and B/C have been measured in the kinetic energy range 0.35-45 GeV/nucleon. The isotopic ratio 7Li/6Li is also determined in the magnetic rigidity interval 2.5-6.3 GV. The secondary to secondary ratios Li/Be, Li/B and Be/B are also reported. These measurements are based on the data collected by the Alpha Magnetic Spectrometer AMS-01 during the STS-91 space shuttle flight in 1998 June. Our experimental results are in substantial agreement with other measurements, where they exist. We describe our light-nuclei data with a diffusive-reacceleration model. A 10-15% overproduction of Be is found in the model predictions and can be attributed to uncertainties in the production cross-section data.

/pdf/relative-composition-and-energy-spectra-of-light-nuclei-in-8upz14xye0.pdf

Relative Composition and Energy Spectra of Light Nuclei in Cosmic Rays: Results from AMS-01

The propagation of linear and nonlinear electrostatic waves is investigated in a magnetized anisotropic electron-positron-ion (e-p-i) plasma with superthermal electrons and positrons. A two-dimensional plasma geometry is assumed. The ions are assumed to be warm and anisotropic due to an external magnetic field. The anisotropic ion pressure is defined using the double adiabatic Chew-Golberger-Low (CGL) theory. In the linear regime, two normal modes are predicted, whose characteristics are investigated parametrically, focusing on the effect of superthermality of electrons and positrons, ion pressure anisotropy, positron concentration and magnetic field strength. A Zakharov-Kuznetsov (ZK) type equation is derived for the electrostatic potential (disturbance) via a reductive perturbation method. The parametric role of superthermality, positron content, ion pressure anisotropy and magnetic field strength on the characteristics of solitary wave structures is investigated. Following Allen and Rowlands [J. Plasma Phys. 53, 63 (1995)], we have shown that the pulse soliton solution of the ZK equation is unstable to oblique perturbations, and have analytically traced the dependence of the instability growth rate on superthermality and ion pressure anisotropy.

Pressure anisotropy effects on nonlinear electrostatic excitations in magnetized electron-positron-ion plasmas

[1] Accurate measurements of under cutoff proton, electron, and positron fluxes in the energy range 007 ÷ 91 GeV have been performed with the Alpha Magnetic Spectrometer at altitudes of 370 ÷ 390 km in the geographic latitude interval ±517° The flux maps as a function of the canonical adiabatic variables L, αo, and energy E are presented and discussed

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004SW000068

High‐energy protons, electrons, and positrons trapped in Earth's radiation belts

Linear and nonlinear coupled drift-ion acoustic waves are investigated in a nonuniform magnetoplasma having kappa distributed electrons and positrons In the linear regime, the role of kappa distribution and positron content on the dispersion relation has been highlighted; it is found that strong superthermality (low value of κ) and addition of positrons lowers the phase velocity via decreasing the fundamental scalelengths of the plasmas In the nonlinear regime, first, coherent nonlinear structure in the form of dipoles and monopoles are obtained and the boundary conditions (boundedness) in the context of superthermality and positron concentrations are discussed Second, in case of scalar nonlinearity, a Korteweg–de Vries-type equation is obtained, which admit solitary wave solution It is found that both compressive and rarefactive solitons are formed in the present model The present work may be useful to understand the low frequency electrostatic modes in inhomogeneous electron positron ion plasmas, which exist in astrophysical plasma situations such as those found in the pulsar magnetosphere

/pdf/coupled-ion-acoustic-and-drift-waves-in-magnetized-d227rr387p.pdf

Coupled ion acoustic and drift waves in magnetized superthermal electron-positron-ion plasmas

Effect of positron density and temperature on the electron acoustic waves in a magnetized dissipative plasma

[1] Accurate measurements of electron and positron fluxes in the energy range 0.2–10 GeV have been performed with the Alpha Magnetic Spectrometer (AMS) at altitudes of 320–390 km in the geographic latitude interval ±51.7°. We focus on the fluxes measured in the regions nearby the South Atlantic Anomaly, defined by the local magnetic values of the magnetic field B (0.21 ≤ B ≤ 0.26 G) at the altitude of AMS. A clear transition from the Stably Trapped population typical of the Inner Van Allen belts to Quasi-Trapped population in the regions underneath the Van Allen belts is observed. The high energy observations demonstrate the relatively higher abundance of positrons in the Inner Van Allen belts, for both the Stably Trapped and the Quasi-Trapped populations. The flux maps as a function of the canonical adiabatic variables L, αo are presented for the interval 0.95 < L < 3, 0° < αo < 90° for electron energies below 10 GeV and positrons energies below 3 GeV. The results are compared with existing data at lower energies.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003JA009844

Leptons with energy >200 MeV trapped near the South Atlantic Anomaly

The Alpha Magnetic Spectrometer (AMS01), a high-sensitivity particle spectrometer, was successfully flown for 10 d in June 1998 (STS91) in the orbit of the International Space Station (51.7 degrees, -380 km). A high-statistics dataset of galactic cosmic rays were measured as a function of geomagnetic latitude, including the primary protons, leptons and helium as well as the trapped and quasi-trapped proton and lepton components. In this paper, the absorbed dose rate owing to the protons, leptons and helium are presented and compared with measurements made by other instruments flown on the same mission.

Absorbed dose rate estimation for protons, leptons and helium observed with AMS01 experiment in low earth orbit during STS-91 mission.

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Leptons with energy >200 MeV trapped near the South Atlantic Anomaly

Absorbed dose rate estimation for protons, leptons and helium observed with AMS01 experiment in low earth orbit during STS-91 mission.