Technical Article

Updated model of cosmic-ray-induced ionization in the atmosphere (CRAC:CRII_v3): Improved yield function and lookup tables

¹ Space Physics and Astronomy Research Unit and Sodankylä Geophysical Observatory, University of Oulu, Linanmaa 90014, Finland
² A.F. Ioffe Physical–Technical Institute, Politechnicheskaya 26, 194021 St. Petersburg, Russia

^* Corresponding author: ilya.usoskin@oulu.fi

Received: 1 March 2024
Accepted: 29 May 2024

Abstract

Cosmic rays, including galactic cosmic rays and solar energetic particles, form the main source of ionization of the low and middle atmosphere, which is important for various chemical and physical effects in the atmosphere. Realistic models able to compute the cosmic-ray-induced ionization (CRII) are used as inputs for chemistry-climate models. One of the most commonly used atmospheric ionization models is CRAC:CRII (Cosmic-Ray Atmospheric Cascade: application to CRII) initially developed in 2004–2006 (version 1) and significantly improved in 2010–2011 (version 2). Here, a new updated version 3 of the CRAC:CRII model is presented which offers a higher accuracy for the middle-upper atmosphere and lower-energy cosmic rays. This is particularly important for studies of the atmospheric effects of solar particle storms. Detailed lookup tables of the ionization yield function are provided for the primary cosmic ray protons and α-particles (the latter representing also heavier cosmic-ray species) along with a practical recipe for their numerical use.