The isotopic composition of anomalous cosmic rays from sampex

Abstract

Measurements of the anomalous cosmic ray (ACR) isotopic composition have been made in three regions of the magnetosphere accessible from the polar Earth orbit of SAMPEX, including the interplanetary medium at high latitudes and geomagnetically trapped ACRs. At those latitudes where ACRs can penetrate the Earth's magnetic field while fully stripped galactic cosmic rays (GCRs) of similar energies are excluded, a pure ACR sample is observed to have the following composition: 15N/N < 0.023, 180/160 < 0.0034, and 22Ne/2~ = 0.077(+0.085,-0.023). We compare our values with those found by previous investigators and with those measured in other samples of solar and galactic material. In particular, a comparison of 22Ne/2~ measurements from various sources implies that GCRs are not simply an accelerated sample of the local interstellar medium.

Galactic cosmic ray neon isotopic abundances measured on ACE

“…The fact that the GCRs show a marked enhancement in 22 Ne/ 20 Ne while the ACRs show good agreement with solar wind abundances is remarkable and is consistent with the SAMPEX results (17). If the ACR ratio is representative of the general ISM, this would indicate that there is a large overabundance of high-energy 22 Ne relative to 20 Ne in the Galaxy (i.e.…”

“…The CRIS OCR 22 Ne/ 20 Ne ratio is approximately constant with a small decrease in the ratio toward lower energies, and is considerably enhanced over the SW ratio. SIS measures a mix of OCRs (dominant at the higher SIS energies) that have a high 22 Ne/ 20 Ne ratio, and ACRs (dominant at the lower SIS energies) that have a ratio similar to SW (16,17). Thus we see that there is a dramatic difference between the CRIS OCR and the low-energy SIS ACR measurements.…”

“…In the tracer method the observed abundances of secondary nuclides such as 21 Ne, 19 F, or 17 O are scaled to determine the secondary contribution to the observed 22 Ne, and thereby to derive the 22 Ne source abundance. A series of leaky-box propagation calculations was carried out using various assumed escape mean free paths.…”

“…The point on the abscissa corresponding to a 0% difference for 21 Ne at Earth gives the best estimate of the 22 Ne source abundance using that secondary as a constraint. Source abundances obtained using 19 F and 17 O secondary tracers were also obtained (not shown) and averaged with the 21 Ne value to obtain a best overall ratio. The measurement uncertainty in the 21 Ne abundance is represented by the vertical dotted lines in Figure 5.…”

Characterization and Physical Explanation of Energetic Particles on Planck HFI Instrument

“…Cosmic rays (CRs) 7,8 at Lagrangian point L2 are essentially composed by massive particles: about 89% of protons, 10% of alpha particles, 1% are the nuclei of heavier elements and less than 1% of electrons like beta particles. The total flux of CRs peaks around 200 MeV, giving a total proton flux of 3000 -4000 particles m −2 sr −1 s −1 GeV −1 .…”