Cosmic rays as regulators of molecular cloud properties

TL;DR

Cosmic rays significantly influence molecular cloud chemistry and magnetic coupling, with magnetic field configurations affecting their ionization rates and the cloud's evolution.

Contribution

This paper demonstrates how magnetic field structures modulate cosmic-ray ionization rates, impacting molecular cloud dynamics and magnetic decoupling.

Findings

Magnetic field configurations reduce cosmic-ray ionization in collapse regions.

Decreased ionization facilitates gas-magnetic field decoupling.

Magnetic effects are crucial in cosmic-ray energy degradation.

Abstract

Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.