# Chemical network reduction in protoplanetary disks

## TL;DR

This paper demonstrates a species-based network reduction method that simplifies complex chemical networks in protoplanetary disks, enabling efficient modeling of major species' abundances in key disk regions.

## Contribution

The study introduces and evaluates a species-based reduction technique that accurately reproduces major chemical abundances with significantly smaller networks in protoplanetary disks.

## Key findings

- Reduced networks with 20-30 species effectively reproduce major species abundances.
- The method works well in disk midplane and surface regions.
- Most major carriers of elements have similar abundances in reduced and full networks.

## Abstract

Protoplanetary disks (PPDs) are characterized by different kinds of gas dynamics and chemistry, which are coupled via ionization, heating and cooling processes, as well as advective and turbulent transport. However, directly coupling gas dynamics with time-dependent chemistry is prohibitively computationally expensive when using comprehensive chemical reaction networks. In this paper, we evaluate the utility of a species-based network reduction method in different disk environments to produce small chemical networks that reproduce the abundances of major species found in large gas-phase chemistry networks. We find that the method works very well in disk midplane and surfaces regions, where approximately 20-30 gas phase species, connected by $\sim$50-60 gas phase reactions, are sufficient to reproduce the targeted ionization fraction and chemical abundances. Most species of the reduced networks, including major carriers of oxygen, carbon and nitrogen, also have similar abundances in the reduced and complete network models. Our results may serve as an initial effort for future hydrodynamic/magnetohydrodynamic simulations of PPDs incorporating time-dependent chemistry in appropriate regions. Accurately modeling the abundances of major species at intermediate disk heights, however, will require much more extended network incorporating gas-grain chemistry and are left for future studies.