neoVULCAN

neoVULCAN is a one-dimensional photochemical kinetics code for planetary and exoplanetary atmospheres. It is a refactored, JAX-accelerated descendant of the original VULCAN code [Tsai2017], [Tsai2021] (upstream repository: shami-EEG/VULCAN), designed to integrate the stiff transport–reaction system

\[\frac{\partial n_i}{\partial t} = \mathcal{P}_i - \mathcal{L}_i - \frac{\partial \phi_i}{\partial z}\]

forward in time until a numerical steady state is reached. Compared to the original VULCAN, neoVULCAN

  • uses JAX for automatic differentiation of the chemistry Jacobian and for vectorised rate evaluations,

  • exposes a library API (vulcan_api.VulcanChemistry) for embedding in three-dimensional general-circulation models,

  • supports both the second-order Rosenbrock (Ros2) and a third-order, L-stable Rosenbrock–Wanner (Rodas3) integrator,

  • implements photochemistry, condensation with particle settling, advection, molecular diffusion with thermal-diffusion drift, and a flexible C–H–N–O–S reaction network.

This documentation collects the mathematical background, the numerical schemes used inside neoVULCAN, a complete reference for the configuration file, and a tour of the code architecture.

Getting started

Theory

Reference

Appendix

Indices and tables