Info<< "Reading physicalProperties\n" << endl;
IOdictionary physicalProperties (
  IOobject (
    "physicalProperties",
    runTime.constant(),
    mesh,
    IOobject::MUST_READ,
    IOobject::NO_WRITE
  )
);
dimensionedScalar muMag (
  "muMag",
  dimensionSet(1, 1, -2, 0, -2, 0, 0),
  physicalProperties
);

Info<< "Reading field sigma\n" << endl;
volScalarField sigma (
  IOobject (
    "sigma",
    runTime.timeName(),
    mesh,
    IOobject::MUST_READ,
    IOobject::AUTO_WRITE
  ),
  mesh
);

volScalarField ElPot  (
  IOobject (
    "ElPot",
    runTime.timeName(),
    mesh,
    IOobject::MUST_READ,
    IOobject::AUTO_WRITE
   ),
   mesh
);

Info<< "Reading field A\n" << endl;
volVectorField A  (
  IOobject (
    "A",
    runTime.timeName(),
    mesh,
    IOobject::MUST_READ,
    IOobject::AUTO_WRITE
  ),
  mesh
);

Info << "Calculating magnetic field B \n" << endl;
volVectorField B  (
  IOobject (
    "B",
    runTime.timeName(),
    mesh,
    IOobject::NO_READ,
    IOobject::AUTO_WRITE
  ),
  fvc::curl(A)
);

volVectorField Je (
  IOobject (
    "Je",
    runTime.timeName(),
    mesh,
    IOobject::NO_READ,
    IOobject::AUTO_WRITE
  ),
  -sigma*(fvc::grad(ElPot))
);