Leighton-Relationship

The NOx (NO + NO₂) photochemical cycle that governs tropospheric ozone — Seinfeld & Pandis (2006) Ch. 6 §6.2, Eqs. 6.5-6.8, pp. 207-212. During daytime three reactions cycle rapidly between NO, NO₂ and O₃: NO₂ + hν → NO + O (λ < 424 nm), O + O₂ + M → O₃ + M, and NO + O₃ → NO₂ + O₂. In the absence of other oxidants this cycle reaches a photostationary state (the Leighton relationship). Implements four algebraic diagnostic relations: (Eq. 6.5) ground-state O-atom steady-state concentration O = j_NO2·[NO₂] / (k_O_O2_M·[O₂]·[M]), (Eq. 6.6) photostationary-state ozone O3_pss = j_NO2·[NO₂] / (k_NO_O3·[NO]) — the Leighton relationship, (Eq. 6.7) the photostationary-state parameter Φ = j_NO2·[NO₂] / (k_NO_O3·[NO]·[O₃]) which is 1 at exact PSS and deviates when peroxy radicals perturb the cycle, and (Eq. 6.8) the net ozone production rate P_O3 = j_NO2·[NO₂] − k_NO_O3·[NO]·[O₃]. Observed-only algebraic system (no time derivatives): nine variables (five inputs NO/NO2/O3/O2/M encoded as parameters, four outputs O/O3_pss/Φ/P_O3 encoded as state) plus three rate-constant parameters (j_NO2, k_O_O2_M, k_NO_O3). Migrated from GasChem.jl@8c12c048 src/nox_photochemistry.jl:88 (`NOxPhotochemistry` @component). Sibling component PhotostationaryState (src/nox_photochemistry.jl:145) migrates separately to photostationary.esm.

Photostationary-state diagnostic for the NO-NO₂-O₃ Leighton cycle — Seinfeld & Pandis (2006) Ch. 6 §6.2, Eqs. 6.6-6.7, pp. 207-212. Computes the photostationary-state parameter Φ = j_NO2·[NO₂] / (k_NO+O₃·[NO]·[O₃]) and its deviation from unity Φ_deviation = Φ - 1. Φ = 1 is the exact Leighton photostationary state (pure NO-NO₂-O₃ cycling, zero net ozone production); Φ > 1 indicates additional oxidants (peroxy radicals HO₂/RO₂ converting NO→NO₂ and producing ozone), Φ < 1 indicates net ozone loss. This observed-only algebraic component is the simplified companion to NOxPhotochemistry (the full Eqs. 6.5-6.8 diagnostic): five variables (three inputs NO/NO₂/O₃ encoded as parameters, two outputs Φ/Φ_deviation as state), two rate parameters (j_NO2, k_NO_O3) plus the dimensionless unity constant `one`, and two algebraic equations. No time derivatives. Migrated from GasChem.jl@8c12c048 src/nox_photochemistry.jl:145 (`PhotostationaryState` @component).