diff --git a/Source/Diagnostics/ComputeDiagFunctors/CMakeLists.txt b/Source/Diagnostics/ComputeDiagFunctors/CMakeLists.txt
index 2ef6af16bfe..f0ff1df2d22 100644
--- a/Source/Diagnostics/ComputeDiagFunctors/CMakeLists.txt
+++ b/Source/Diagnostics/ComputeDiagFunctors/CMakeLists.txt
@@ -12,5 +12,6 @@ foreach(D IN LISTS WarpX_DIMS)
         BackTransformFunctor.cpp
         BackTransformParticleFunctor.cpp
         ParticleReductionFunctor.cpp
+        ProcessorMapFunctor.cpp
     )
 endforeach()
diff --git a/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.H b/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.H
new file mode 100644
index 00000000000..506f2501d43
--- /dev/null
+++ b/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.H
@@ -0,0 +1,45 @@
+#ifndef WARPX_PROCESSORMAPFUNCTOR_H_
+#define WARPX_PROCESSORMAPFUNCTOR_H_
+
+#include "ComputeDiagFunctor.H"
+
+#include <AMReX_BaseFwd.H>
+
+/**
+ * \brief Functor to cell-center MF and store result in mf_out.
+ */
+class ProcessorMapFunctor final : public ComputeDiagFunctor
+{
+public:
+    /** Constructor.
+     *
+     * \param[in] mf_src source multifab.
+     * \param[in] lev level of multifab. Used for averaging in rz.
+     * \param[in] crse_ratio for interpolating field values from the simulation MultiFab, src_mf,
+                  to the output diagnostic MultiFab, mf_dst.
+     * \param[in] convertRZmodes2cartesian (in cylindrical) whether to
+     *            sum all modes in mf_src before cell-centering into dst multifab.
+     * \param[in] ncomp Number of component of mf_src to cell-center in dst multifab.
+     */
+    ProcessorMapFunctor(const amrex::MultiFab * mf_src, int lev,
+                      amrex::IntVect crse_ratio,
+                      bool convertRZmodes2cartesian=true, int ncomp=1);
+    /** \brief Cell-center m_mf_src and write the result in mf_dst.
+     *
+     * In cylindrical geometry, by default this functor average all components
+     * of a MultiFab and writes into one single component.
+     *
+     * \param[out] mf_dst output MultiFab where the result is written
+     * \param[in] dcomp first component of mf_dst in which cell-centered
+     *            data is stored
+     */
+    void operator()(amrex::MultiFab& mf_dst, int dcomp, int /*i_buffer=0*/) const override;
+private:
+    /** pointer to source multifab (can be multi-component) */
+    amrex::MultiFab const * const m_mf_src = nullptr;
+    int m_lev; /**< level on which mf_src is defined (used in cylindrical) */
+    /**< (for cylindrical) whether to average all modes into 1 comp */
+    bool m_convertRZmodes2cartesian;
+};
+
+#endif // WARPX_CELLCENTERFUNCTOR_H_
diff --git a/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.cpp b/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.cpp
new file mode 100644
index 00000000000..33cb8cb9233
--- /dev/null
+++ b/Source/Diagnostics/ComputeDiagFunctors/ProcessorMapFunctor.cpp
@@ -0,0 +1,37 @@
+#include "ProcessorMapFunctor.H"
+
+#include "WarpX.H"
+
+#include <AMReX.H>
+#include <AMReX_IntVect.H>
+#include <AMReX_MultiFab.H>
+
+ProcessorMapFunctor::ProcessorMapFunctor(amrex::MultiFab const * mf_src, int lev,
+                                     amrex::IntVect crse_ratio,
+                                     bool convertRZmodes2cartesian, int ncomp)
+    : ComputeDiagFunctor(ncomp, crse_ratio), m_mf_src(mf_src), m_lev(lev),
+      m_convertRZmodes2cartesian(convertRZmodes2cartesian)
+{}
+
+void
+ProcessorMapFunctor::operator()(amrex::MultiFab& mf_dst, int dcomp, const int /*i_buffer*/) const
+{
+    std::unique_ptr<amrex::MultiFab> tmp;
+    tmp = std::make_unique<amrex::MultiFab>(m_mf_src->boxArray(), m_mf_src->DistributionMap(), 1, m_mf_src->nGrowVect());
+
+    auto& warpx = WarpX::GetInstance();
+    const amrex::DistributionMapping& dm = warpx.DistributionMap(m_lev);
+    for (amrex::MFIter mfi(*tmp, false); mfi.isValid(); ++mfi)
+    {
+        auto bx = mfi.growntilebox(tmp->nGrowVect());
+        auto arr = tmp->array(mfi);
+        int iproc = dm[mfi.index()];
+        amrex::ParallelFor(bx,
+            [=] AMREX_GPU_DEVICE(int i, int j, int k)
+            {
+                arr(i,j,k) = iproc;
+            });
+    }
+    InterpolateMFForDiag(mf_dst, *tmp, dcomp, warpx.DistributionMap(m_lev),
+                         m_convertRZmodes2cartesian);
+}
diff --git a/Source/Diagnostics/FullDiagnostics.cpp b/Source/Diagnostics/FullDiagnostics.cpp
index d93c67fe893..838d4789e32 100644
--- a/Source/Diagnostics/FullDiagnostics.cpp
+++ b/Source/Diagnostics/FullDiagnostics.cpp
@@ -7,6 +7,7 @@
 #include "ComputeDiagFunctors/PartPerGridFunctor.H"
 #include "ComputeDiagFunctors/ParticleReductionFunctor.H"
 #include "ComputeDiagFunctors/RhoFunctor.H"
+#include "ComputeDiagFunctors/ProcessorMapFunctor.H"
 #include "Diagnostics/Diagnostics.H"
 #include "Diagnostics/ParticleDiag/ParticleDiag.H"
 #include "FlushFormats/FlushFormat.H"
@@ -659,6 +660,8 @@ FullDiagnostics::InitializeFieldFunctors (int lev)
             m_all_field_functors[lev][comp] = std::make_unique<DivBFunctor>(warpx.get_array_Bfield_aux(lev), lev, m_crse_ratio);
         } else if ( m_varnames[comp] == "divE" ){
             m_all_field_functors[lev][comp] = std::make_unique<DivEFunctor>(warpx.get_array_Efield_aux(lev), lev, m_crse_ratio);
+        } else if ( m_varnames[comp] == "proc_number" ){
+            m_all_field_functors[lev][comp] = std::make_unique<ProcessorMapFunctor>(warpx.get_pointer_Efield_aux(lev,0), lev, m_crse_ratio);
         }
         else {