rate_ISO2

{
  "reference": {
    "notes": "source_ref: GasChem.jl@8c12c048482b515fb8eb2110bf8ab4b4f4e71309:src/geoschem_ratelaws.jl:993 (`rate_ISO2` rate-law builder function).\n\nRate law for the ISOP + OH channel forming HPALD / fragmentation products: k = a0*exp(b0/T)*k2 * C, where k2 is the same tunnelling-modulated branching term as rate_ISO1 (this is its complement channel).\n\nMigration shape: the upstream `rate_ISO2` 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_rate_ISO2` pins k at the parameter defaults to the value asserted by the `@testitem \"rate_ISO2\"` 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": {
    "T": {
      "type": "parameter",
      "default": 293.0,
      "description": "Air temperature (K). Default 293.0 K is the scenario temperature of the upstream geoschem_ratelaws_test.jl `RateLawSetup` test snippet."
    },
    "num_density": {
      "type": "parameter",
      "default": 44.834554813693856,
      "description": "Number density of air (mol/m^3). Default 44.834554813693856 mol/m^3 equals 2.7e19 molec/cm^3 — the upstream test value 2.7e19/N_A*cm3_m3 (N_A = 6.02214076e23, cm3_m3 = 1.0e6)."
    },
    "a0": {
      "type": "parameter",
      "default": 1e-11,
      "description": "Overall ISOP + OH pre-exponential."
    },
    "b0": {
      "type": "parameter",
      "default": 390.0,
      "description": "Overall ISOP + OH temperature term. [K]"
    },
    "c0": {
      "type": "parameter",
      "default": 0.3,
      "description": "Branching-term scale factor."
    },
    "d0": {
      "type": "parameter",
      "default": 1.0,
      "description": "k0 pre-exponential of the branching term."
    },
    "e0": {
      "type": "parameter",
      "default": 380.0,
      "description": "k0 temperature term of the branching term. [K]"
    },
    "f0": {
      "type": "parameter",
      "default": 1.0,
      "description": "k1 pre-exponential of the branching term."
    },
    "g0": {
      "type": "parameter",
      "default": 380.0,
      "description": "k1 temperature term of the branching term. [K]"
    },
    "k": {
      "type": "unknown",
      "description": "Reaction rate coefficient produced by the rate_ISO2 rate law, output in ppb^-1*s^-1. Defined by one algebraic equation; the system carries no time derivative."
    }
  },
  "equations": [
    {
      "lhs": "k",
      "rhs": {
        "op": "*",
        "args": [
          "a0",
          {
            "op": "exp",
            "args": [
              {
                "op": "/",
                "args": [
                  "b0",
                  "T"
                ]
              }
            ]
          },
          {
            "op": "/",
            "args": [
              {
                "op": "*",
                "args": [
                  "c0",
                  {
                    "op": "*",
                    "args": [
                      "d0",
                      {
                        "op": "exp",
                        "args": [
                          {
                            "op": "/",
                            "args": [
                              "e0",
                              "T"
                            ]
                          }
                        ]
                      },
                      {
                        "op": "exp",
                        "args": [
                          {
                            "op": "/",
                            "args": [
                              100000000.0,
                              {
                                "op": "^",
                                "args": [
                                  "T",
                                  3.0
                                ]
                              }
                            ]
                          }
                        ]
                      }
                    ]
                  }
                ]
              },
              {
                "op": "+",
                "args": [
                  {
                    "op": "*",
                    "args": [
                      "d0",
                      {
                        "op": "exp",
                        "args": [
                          {
                            "op": "/",
                            "args": [
                              "e0",
                              "T"
                            ]
                          }
                        ]
                      },
                      {
                        "op": "exp",
                        "args": [
                          {
                            "op": "/",
                            "args": [
                              100000000.0,
                              {
                                "op": "^",
                                "args": [
                                  "T",
                                  3.0
                                ]
                              }
                            ]
                          }
                        ]
                      }
                    ]
                  },
                  {
                    "op": "*",
                    "args": [
                      "f0",
                      {
                        "op": "exp",
                        "args": [
                          {
                            "op": "/",
                            "args": [
                              "g0",
                              "T"
                            ]
                          }
                        ]
                      }
                    ]
                  }
                ]
              }
            ]
          },
          {
            "op": "*",
            "args": [
              "num_density",
              1e-09,
              6.02214076e+17
            ]
          }
        ]
      }
    }
  ],
  "tests": [
    {
      "id": "upstream_rate_ISO2",
      "description": "Reproduces the upstream `rate_ISO2` 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 `rate_ISO2` — and the rate coefficient k is pinned to the upstream expected value 0.3009403732544113.",
      "parameter_overrides": {},
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "k",
          "time": 0.0,
          "expected": 0.3009403732544113
        }
      ]
    }
  ]
}