Replace "none" BC with Neumann for electrostatic (#3483)

* Replace "none" BC with Neumann for electrostatic

* Added checking for Neumann boundaries

* Updated documentation regarding Neumann BCs

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/Source/Utils/WarpXAlgorithmSelection.H b/Source/Utils/WarpXAlgorithmSelection.H
index 97dd3b89f..9346159ab 100644
--- a/Source/Utils/WarpXAlgorithmSelection.H
+++ b/Source/Utils/WarpXAlgorithmSelection.H
@@ -119,7 +119,8 @@ struct FieldBoundaryType {
         Damped = 4,   // Fields in the guard cells are damped for PSATD
                      //in the moving window direction
         Absorbing_SilverMueller = 5, // Silver-Mueller boundary condition
-        None = 6     // The fields values at the boundary are not updated. This is
+        Neumann = 6, // For electrostatic, the normal E is set to zero
+        None = 7     // The fields values at the boundary are not updated. This is
                      // useful for RZ simulations, at r=0.
     };
 };