Operator Overview

Operators in GUERNICA are modular and are enabled through the operators entry of the [components] section. This allows each simulation to include only the physical processes needed for a given case. Advection is always active and is not listed.

Operator	operators entry	Input section	Required species
Ionization	ionization	[ionization]	n, e
Recombination	recombination	[recombination]	n (plus e, i for Janev1987)
Charge Exchange	charge_exchange	[charge_exchange]	n, i
Neutral-Neutral	neutral_neutral	[neutral_neutral]	n
Source	source	[source]	n

Species are specified through the species entry under [components]. GUERNICA evolves only the neutral distribution function n. Electrons e and ions i are prescribed background populations: their density, temperature, and drift profiles are inputs to the operators, not independently evolved species.

For each species listed in the simulation, the initial distribution (for n) or the background fields (for e and i) are defined in a [<species>:init] section. Any spatial dependence is then specified separately through one or more [profile:<name>] sections. This separation allows a distribution type and a spatial profile to be combined flexibly when setting up a case. The background fields are projected onto the DG space once at startup and saved to profile_files/ in the run directory.

In transient mode, every operator is added to the RK3 right-hand side. In steady mode, sources (source, recombination) are grouped with advection, while loss and collision operators (ionization, charge exchange, neutral–neutral) are kept in a separate collision container. Both groups contribute to the same steady residual. Each operator also contributes a channel to the end-of-run reaction rate maps and the global particle and energy budget (see Post Processing).

A complete list of available distribution function initialization types and profile types is provided in Inputs Reference.