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Why Heavy Cosmic-Ray Nuclei Unexpectedly Grow with Energy ✛ ✎ ✦

Original: "To the interpretation of the upturn observed by ATIC in heavy nuclei to iron ratios"
· A. D. Panov, N. V. Sokolskaya, V. I. Zatsepin
arXiv:1303.6102 · 2013-03-25 · arXiv non-exclusive · independent analysis · 1 min
High Energy
A closed-galaxy model with local bubbles explains the mysterious rise in the ratio of heavy nuclei to iron in ATIC data.

The ATIC balloon rose over Antarctica and caught particles older than Earth itself. Among them are atomic nuclei from sulfur to chromium, and the higher their energy, the larger their share compared with iron. The standard 'leaky box' model predicted the opposite: heavy nuclei should dissolve like salt in water. But the data stubbornly rose.

Cosmic rays are high-energy charged particles flying in from space. Secondary nuclei are born when primary ones collide with interstellar gas.

The authors returned to a forgotten idea from 1977: the galaxy is not a 'leaky box' but a closed room with bubbles. Inside each bubble are sources, like lamps in soap bubbles. The Sun sits in one of them, and we see not only the light from our own lamp but also the glows from others, seeping through the walls. A model with a 20% volume flux fraction reproduced the rise: first the ratio falls, as expected, and then it grows: this is the light from other bubbles coming into play.

Whole graph →

The local bubble, which hosts the Sun, is a real region of tenuous hot gas about 100 parsecs across, created by supernova explosions. If the CG+B model is correct, we literally live inside a 'cauldron' where cosmic rays are brewed.

\frac{I_{\Sigma S}}{I_{Fe}} = \sum_{i=1}^{k} \frac{\kappa_{N_i,Fe}}{\kappa_{N_i}^{esc}(\epsilon) + \kappa_{N_i}}
Sum over all secondary nuclei Ni of the ratio of the partial production path length from iron to the sum of inverse escape and nuclear interaction lengths.
Q_{bulk}(\epsilon) = \frac{\kappa^{esc}(\epsilon)}{\kappa^{esc}(\epsilon) + \kappa} Q(\epsilon)
The spectrum of particles escaping the bubble and forming the bulk flux equals the original source spectrum multiplied by the escape probability before interaction.
\frac{I_{N_i}(\epsilon)}{I_{Fe}(\epsilon)} = \frac{\kappa_{N_i,Fe}}{\kappa_{N_i}^{esc}(\epsilon) + \kappa_{N_i}} + K \frac{\kappa_{N_i,Fe}}{\kappa_{N_i}} \frac{\kappa_{Fe}^{esc}(\epsilon)}{\kappa_{Fe}} \frac{1 + K \frac{\kappa_{Fe}^{esc}(\epsilon)}{\kappa_{Fe}}}{1 + K \frac{\kappa_{Fe}^{esc}(\epsilon)}{\kappa_{Fe}}}
The total ratio is the sum of the local component (first term) and the bulk flux contribution (second term), where K is the bulk flux fraction.
Scientists
Bernhard RiemannJoseph WeberKarl SchwarzschildKip ThorneRainer WeissAlbert Einstein
Concepts
atomic nucleus active galactic nucleus spectral index reaction rate iron proton mass neutron mass deuteron peak neutron skin lead nucleus nuclear structure nuclear reactor accretion rate galactic center proton spectroscopy scalar spectral index iron line katrin radiation dominated era