Propagation and energy deposition of cosmic rays’ muons on terrestrial environments

Abstract

Earth is constantly struck by radiation coming from the interstellar medium. The very low energy end of the spectrum is shielded by the geomagnetic field but charged particles with energies higher than the geomagnetic cutoff will penetrate the atmosphere and are likely to interact, giving rise to secondary particles. Some astrophysical events, such as gamma ray bursts and supernovae, when happening at short distances, may affect the planet's biosphere due to the temporary enhanced radiation flux. Muons are abundantly produced by high energy cosmic rays in the Earth's atmosphere. These particles, due to their low cross section, are able to penetrate deep underground and underwater, with the possibility of affecting biological niches normally considered shielded from radiation. We investigate the interaction of muons produced by high energy cosmic rays on Earth's atmosphere using the Geant4 toolkit. We analyze penetration power in water and crust and also the interaction effects within bacteria-like material according to particle type and energy, and notice the possibility of off-track damage due to secondary particles.

Muon Radiation Dose and Marine Megafaunal Extinction at the end-Pliocene Supernova

“…The small contribution to the dose from the very low energy part of the spectrum (<1GeV) increases with depth surpassing the surface contribution as can be observed at z = 250 m. This is due to the muons energy loss as they traverse water, shifting muons at mid energy range to lower energies. This was also noticed in a similar analysis in [15]. However, this contribution will decrease faster with higher depths such that it goes below the surface curve again at z = 500 m. This energy loss also renders the flattening and decrease of both underwater curves observed up to ~100 GeV.…”

“…In this method the trajectories can be resumed by the occurrence of the particle decay or due to capture at rest. As shown in [15], the generated secondaries are mostly electrons and gammas and they will likely cause a lateral displacement of ∼1m so still typically inside the large volumes we are interested in.…”

“…Benitez et al noticed the proximity of the SN timing to the PP extinction and proposed the UV mechanism as related to the extinction [14]. However, there was also awareness of the effect of muons on the subsurface from cosmic ray showers [15]. All of these works were limited by a relative lack of information on source electromagnetic and cosmic ray (CR) emissions.…”

Hypothesis: Muon Radiation Dose and Marine Megafaunal Extinction at the End-Pliocene Supernova

“…In this method the trajectories can be resumed by the occurrence of the particle decay or due to capture at rest. As shown in (Marinho et al, 2014), the generated secondaries are mostly electrons and gammas and they will likely cause a lateral displacement of ∼1m so still typically inside the large volumes we are interested in.…”

Terrestrial effects of moderately nearby supernovae

“…The greatest source of muons under normal conditions is cosmic rays, and they contribute about a sixth of the radiation normally encountered on the ground. They are extremely penetrating because they do not interact strongly with ordinary matter (Marinho et al 2014). However, they are present in such great abundance that they have a substantial effect; due to their penetration they can have effects on biota as deep as a kilometer in water or several hundred meters underground.…”