add external fields after initial E solve

Signed-off-by: roelof-groenewald <[email protected]>

Source/Initialization/WarpXInitData.cpp

@@ -578,6 +578,11 @@ WarpX::InitData ()
         if (electrostatic_solver_id == ElectrostaticSolverAlgo::LabFrameElectroMagnetostatic) {
             ComputeMagnetostaticField();
         }
+        // Add external fields to the fine patch fields. This makes it so that the
+        // net fields are the sum of the field solutions and any external fields.
+        for (int lev = 0; lev <= max_level; ++lev) {
+            AddExternalFields(lev);
+        }
     }
 
     if (restart_chkfile.empty() || write_diagnostics_on_restart) {
@@ -1013,8 +1018,6 @@ WarpX::InitLevelData (int lev, Real /*time*/)
 
     // load external grid fields into E/Bfield_fp_external multifabs
     LoadExternalFields(lev);
-    // add the external fields to the fine patch fields as initial conditions for the fields
-    AddExternalFields(lev);
 
     if (costs[lev]) {
         const auto iarr = costs[lev]->IndexArray();