Use explicit pseudotimestep for electrons when ion timestep not IMEX

If the ion timestep is not IMEX, the electron pressure cannot be advanced implicitly, which is required for a stable implicit electron timestep. Therefore when not using an IMEX timestep method for ions, use explicit timestepping for electron pseudotimestepping loop.
mabarnes · Jan 12, 2025 · 82e8765 · 82e8765
1 parent 8666711
commit 82e8765
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Showing 2 changed files with 7 additions and 3 deletions.
diff --git a/moment_kinetics/src/initial_conditions.jl b/moment_kinetics/src/initial_conditions.jl
@@ -706,6 +706,8 @@ function initialize_electron_pdf!(scratch, scratch_electron, pdf, moments, field
             if !skip_electron_solve
                 # Can't let this counter stay set to 0
                 t_params.electron.dfns_output_counter[] = max(t_params.electron.dfns_output_counter[], 1)
+                implicit_electron_pseudotimestep = (nl_solver_params.electron_advance !== nothing)
+                electron_solution_method = implicit_electron_pseudotimestep ? "backward_euler" : "artificial_time_derivative"
                 success =
                     @views update_electron_pdf!(scratch_electron, pdf.electron.norm,
                                                 moments, fields.phi, r, z, vperp, vpa,
@@ -720,7 +722,8 @@ function initialize_electron_pdf!(scratch, scratch_electron, pdf, moments, field
                                                 io_electron=io_initial_electron,
                                                 initial_time=code_time,
                                                 residual_tolerance=t_input["initialization_residual_value"],
-                                                evolve_ppar=true)
+                                                evolve_ppar=true,
+                                                solution_method=electron_solution_method)
                 if success != ""
                     error("!!!max number of iterations for electron pdf update exceeded!!!\n"
                           * "Stopping at $(Dates.format(now(), dateformat"H:MM:SS"))")
@@ -795,7 +798,8 @@ function initialize_electron_pdf!(scratch, scratch_electron, pdf, moments, field
                                          max_electron_pdf_iterations,
                                          max_electron_sim_time;
                                          io_electron=io_initial_electron,
-                                         evolve_ppar=true, ion_dt=t_params.dt[])
+                                         evolve_ppar=true, ion_dt=t_params.dt[],
+                                         solution_method=electron_solution_method)
             end
             if success != ""
                 error("!!!max number of iterations for electron pdf update exceeded!!!\n"

diff --git a/moment_kinetics/src/time_advance.jl b/moment_kinetics/src/time_advance.jl
@@ -2551,7 +2551,7 @@ moments and moment derivatives
                electron_vpa_advect, scratch_dummy, t_params.electron, collisions,
                composition, external_source_settings, num_diss_params,
                nl_solver_params.electron_advance, max_electron_pdf_iterations,
-               max_electron_sim_time)
+               max_electron_sim_time, solution_method="artificial_time_derivative")
             success = kinetic_electron_success
         end
     end