Chemistry and cosmic rays: the terrestrial planet-forming region of disks

Donna Rodgers-Lee

Stellar cosmic rays, also known as stellar energetic particles, are energetic particles accelerated by low-mass stars. Young stars are expected to accelerate more stellar cosmic rays, and to higher energies, than the present-day Sun due to strong magnetic fields. This means that stellar cosmic rays are an important source of ionisation for protoplanetary disks and will influence disk chemistry. The chemical inventory of protoplanetary disks defines the reservoir of material available for planet formation.

Our recent results investigate the impact of stellar cosmic rays on volatile carbon chemistry in the terrestrial planet-forming region of protoplanetary disks. To do this, we combined a cosmic ray transport model with a chemical model. Here, we show how stellar cosmic rays lead to distinct observable signatures, such as the depletion of carbon monoxide gas in the inner region of protoplanetary disks. JWST observations with the Mid InfraRed Instrument will probe this region and may detect evidence of stellar cosmic rays impacting chemistry in protoplanetary disks for the first time.