Energy Spectra of Primary and Secondary Cosmic-Ray Nuclei Measured With Tracer

Abstract

The TRACER cosmic-ray detector, first flown on long-duration balloon (LDB) in 2003 for observations of the major primary cosmic-ray nuclei from oxygen (Z = 8) to iron (Z = 26), has been upgraded to also measure the energies of the lighter nuclei, including the secondary species boron (Z = 5). The instrument was used in another LDB flight in 2006. The properties and performance of the modified detector system are described, and the analysis of the data from the 2006 flight is discussed. The energy spectra of the primary nuclei carbon (Z = 6), oxygen, and iron over the range from 1 GeV amu −1 to 2 TeV amu −1 are reported. The data for oxygen and iron are found to be in good agreement with the results of the previous TRACER flight. The measurement of the energy spectrum of boron also extends into the TeV amu −1 region. The relative abundances of the primary nuclei, such as carbon, oxygen, and iron, above ∼ 10 GeV amu −1 are independent of energy, while the boron abundance, i. e. the B/C abundance ratio, decreases with energy as expected. However, there is an indication that the previously reported E −0.6 dependence of the B/C ratio does not continue to the highest energies.

GeV-TeV cosmic-ray spectral anomaly as due to reacceleration by weak shocks in the Galaxy

“…Even for the steeper source spectrum assumed for the iron nuclei as compared to the proton and helium nuclei, the reacceleration effect is hard to notice in Fig. 7, and the model spectrum above ∼20 GeV/n (Panov et al 2007), CRN (Swordy et al 1990), HEAO (Engelmann et al 1990), and TRACER (Obermeier et al 2011). follows approximately a single power law, unlike the proton and helium spectra. Thus, our present model predicts a mass dependent spectral hardening, which can be used to differentiate it from other models in the future.…”

“…Model parameters used: η = 1.02, D 0 = 9 × 10 28 cm 2 s −1 , ρ 0 = 3 GV, a = 0.33, q C = 2.24, q O = 2.26, s = 4.5, p c = 1 PeV/c, f C = 0.024%, f O = 0.025%,ν = 25 SNe Myr −1 kpc −2 and φ = 450 MV. Data: HEAO (Engelmann et al 1990), CRN (Swordy et al 1990), CREAM (Ahn et al 2008), AMS-01 (Aguilar et al 2010), ATIC (Panov et al 2008;Orth et al 1978;Simon et al 1980;Webber et al 1985), and TRACER (Obermeier et al 2011). energy spectra shown in Fig. 2 are also observed in the ratio.…”

“…Figure 4 shows the result on the boron-to-carbon ratio (solid line) along with the measurement data. The data are from High Energy Astronomy Observatory Program (HEAO: Engelmann et al 1990), Cosmic Ray Nuclei Experiment (CRN; Swordy et al 1990), CREAM (Ahn et al 2008), Alpha Magnetic Spectrometer (AMS-01; Aguilar et al 2010), ATIC (Panov et al 2008;Orth et al 1978;Simon et al 1980;Webber et al 1985), and TRACER (Obermeier et al 2011). For comparison, we have also shown the best-fit result for the case of pure diffusion (dashed line), i.e., without reacceleration (η = 0), taken from Thoudam & Hörandel (2013).…”

“…5. The solid line represents our results, and the data are taken from CREAM (Ahn et al 2009), ATIC (Panov et al 2007), CRN (Müller et al 1991;Swordy et al 1990), HEAO (Engelmann et al 1990), and TRACER (Obermeier et al 2011). The carbon and oxygen source parameters used are (q C = 2.24, f C = 0.024%), and (q O = 2.26, f O = 0.025%) respectively, where the f 's are given in units of 10 51 ergs.…”

“…4. Data: CREAM (Ahn et al 2009), ATIC (Panov et al 2007), CRN (Müller et al 1991;Swordy et al 1990), HEAO (Engelmann et al 1990), and TRACER (Obermeier et al 2011). the normal component. The spectral roll-off above ∼10 5 GeV/n is due to the assumed exponential cutoff of the source spectrum at p c which we keep fixed at 10 6 GeV/c for protons.…”