constant_k_1

Description

GEOS-Chem gas-phase reaction rate laws — the 37 rate-coefficient builder functions of GasChem.jl src/geoschem_ratelaws.jl, adapted from the GEOS-Chem KPP/fullchem mechanism (github.com/geoschem/geos-chem, commit 4722f288). Each builder computes a single reaction rate coefficient k from temperature and air number density: constant rates (constant_k, constant_k_1), modified-Arrhenius forms in ppb and SI molecular units (arrhenius_ppb, arrhenius_ppb_3, arrhenius_mlc_SI, arrhenius_mlc_1, arrplus_, tunplus_), Troe / third-body pressure-dependent falloff rates (arr_3rdbody, arr_3rdbody_1, rate_OHCO, rate_PAN_abab, rate_PAN_acac, eq_const, eq_const_1), and a family of mechanism-specific rates for HO2, RO2+NO, isoprene, glycolaldehyde, DMS and HNO3 chemistry. Each rate law is migrated as an independent purely-algebraic model: the inputs (T, num_density, Arrhenius coefficients) are parameters, the rate coefficient k is the single state variable defined by one algebraic equation, and an inline test reproduces the rate constant asserted by the corresponding @testitem in GasChem.jl test/geoschem_ratelaws_test.jl (compiled at T=293 K, num_density = 2.7e19 molec/cm^3). The GEOS-Chem license applies (github.com/geoschem/geos-chem/blob/main/LICENSE.txt).

Reference

_source_ref: GasChem.jl@8c12c048482b515fb8eb2110bf8ab4b4f4e71309:src/geoschem_ratelaws.jl:27 (constant_k_1 rate-law builder function).

Constant rate coefficient for a first-order reaction: k = c, the supplied first-order coefficient passed through unchanged (s^-1).

Migration shape: the upstream constant_k_1 returns a Catalyst ReactionSystem carrying zero reactions and one variable k(t) bound by a single algebraic equation k ~ (the @constants in the source are MTK unit-bookkeeping; their numeric values N_A=6.02214076e23, cm3_m3=1.0e6, ppb_unit=1.0e-9, k_unit_inv=1.0e6 are folded into the .esm expression AST as literals). It is migrated here as a purely-algebraic model: the rate-law inputs (T, num_density, Arrhenius coefficients) are type: parameter, the output k is the single type: state variable, and equations holds the one defining equation. No equation carries a D(.) operator, so the trajectory is constant in time and the inline test samples at t=0 (the observed-only convention of sibling files multiple_removal.esm / ope.esm).

Units: variables carry no units field — the rate expression folds the upstream MTK unit conversions into numeric literals, so every quantity is nominally dimensionless to the structural validator. This is the convention of the sibling GEOS-Chem file geoschem_fullchem.esm; physical units are documented in prose in each variable’s description.

Tolerance rationale (model-level rel=1e-8 / abs=1e-30): the rate law is a single closed-form algebraic expression evaluated once (no time integration, no stiff dynamics). rel=1e-8 sits at the upstream Julia approximate-equality default (approx uses rtol=sqrt(eps(Float64))=~1.49e-8) and comfortably absorbs the libm exp / ^ / log10 rounding differences between the Julia reference values and the Python ESS runner; abs=1e-30 is a near-zero floor that gates no assertion here (the smallest pinned rate constant across the file is eq_const k=~2.1e-27).

Upstream test reproduction: the inline test upstream_constant_k_1 pins k at the parameter defaults to the value asserted by the @testitem "constant_k_1" block in GasChem.jl test/geoschem_ratelaws_test.jl, which compiles the rate law at T=293.0 K and num_density=2.7e19/N_A*cm3_m3 mol/m^3 and checks the resulting rate constant k._

Parameters

Observed

Observed expressions

Reaction rate coefficient produced by the constant_k_1 rate law, output in s^-1. Defined by one algebraic equation; the system carries no time derivative.

Raw .esm

{
  "reference": {
    "notes": "source_ref: GasChem.jl@8c12c048482b515fb8eb2110bf8ab4b4f4e71309:src/geoschem_ratelaws.jl:27 (`constant_k_1` rate-law builder function).\n\nConstant rate coefficient for a first-order reaction: k = c, the supplied first-order coefficient passed through unchanged (s^-1).\n\nMigration shape: the upstream `constant_k_1` returns a Catalyst `ReactionSystem` carrying zero reactions and one variable k(t) bound by a single algebraic equation k ~ <rate expression> (the @constants in the source are MTK unit-bookkeeping; their numeric values N_A=6.02214076e23, cm3_m3=1.0e6, ppb_unit=1.0e-9, k_unit_inv=1.0e6 are folded into the .esm expression AST as literals). It is migrated here as a purely-algebraic `model`: the rate-law inputs (T, num_density, Arrhenius coefficients) are `type: parameter`, the output k is the single `type: state` variable, and `equations` holds the one defining equation. No equation carries a D(.) operator, so the trajectory is constant in time and the inline test samples at t=0 (the observed-only convention of sibling files multiple_removal.esm / ope.esm).\n\nUnits: variables carry no `units` field — the rate expression folds the upstream MTK unit conversions into numeric literals, so every quantity is nominally dimensionless to the structural validator. This is the convention of the sibling GEOS-Chem file geoschem_fullchem.esm; physical units are documented in prose in each variable's `description`.\n\nTolerance rationale (model-level rel=1e-8 / abs=1e-30): the rate law is a single closed-form algebraic expression evaluated once (no time integration, no stiff dynamics). rel=1e-8 sits at the upstream Julia approximate-equality default (`approx` uses rtol=sqrt(eps(Float64))=~1.49e-8) and comfortably absorbs the libm exp / ^ / log10 rounding differences between the Julia reference values and the Python ESS runner; abs=1e-30 is a near-zero floor that gates no assertion here (the smallest pinned rate constant across the file is eq_const k=~2.1e-27).\n\nUpstream test reproduction: the inline test `upstream_constant_k_1` pins k at the parameter defaults to the value asserted by the `@testitem \"constant_k_1\"` block in GasChem.jl test/geoschem_ratelaws_test.jl, which compiles the rate law at T=293.0 K and num_density=2.7e19/N_A*cm3_m3 mol/m^3 and checks the resulting rate constant k."
  },
  "tolerance": {
    "rel": 1e-08,
    "abs": 1e-30
  },
  "variables": {
    "c": {
      "type": "parameter",
      "default": 1.8e-12,
      "description": "First-order rate coefficient. [s^-1]"
    },
    "k": {
      "type": "unknown",
      "description": "Reaction rate coefficient produced by the constant_k_1 rate law, output in s^-1. Defined by one algebraic equation; the system carries no time derivative."
    }
  },
  "equations": [
    {
      "lhs": "k",
      "rhs": {
        "op": "*",
        "args": [
          "c",
          1.0
        ]
      }
    }
  ],
  "tests": [
    {
      "id": "upstream_constant_k_1",
      "description": "Reproduces the upstream `constant_k_1` rate-law test (GasChem.jl test/geoschem_ratelaws_test.jl). All parameters are at their declared defaults — the exact coefficient values the upstream @testitem passes to `constant_k_1` — and the rate coefficient k is pinned to the upstream expected value 1.8e-12.",
      "parameter_overrides": {},
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "k",
          "time": 0.0,
          "expected": 1.8e-12
        }
      ]
    }
  ]
}