diff --git a/plotter.py b/plotter.py
index 87b144e..2c0e08e 100644
--- a/plotter.py
+++ b/plotter.py
@@ -1091,7 +1091,7 @@ class Plotter(Aggregator, BaseProcessor):
                 self,
                 partial(self._plot_hist, "cos_pdf"),
                 "cos-PDF",
-                dependencies=["cos_pdf"],
+                dependencies=["cos_pdf", "mwa_speed"],
             ),
             "avg_coldens_pdf": PlotRule(
                 self,
diff --git a/postprocessor.py b/postprocessor.py
index 2d7879b..56d4591 100644
--- a/postprocessor.py
+++ b/postprocessor.py
@@ -8,14 +8,6 @@ vol_func = lambda dset: dset["dx"] ** 3  # Volume function
 getter_T = lambda dset: dset["P"] / dset["rho"]  # Temperature
 
 
-def getter_abs_cos_vB(dset):
-    B_norm = np.sqrt(np.sum(dset["Br"] ** 2, axis=1))
-    v_norm = np.sqrt(np.sum(dset["vel"] ** 2, axis=1))
-    # Compute the dot product in each cell
-    dot_prod = np.einsum("ij,ij->i", dset["vel"], dset["Br"])
-    return np.abs(dot_prod) / (v_norm * B_norm)
-
-
 def getter_B_int(dset):
     B_norm = np.sqrt(np.sum(dset["Br"] ** 2, axis=1))
     return B_norm
@@ -341,6 +333,20 @@ class PostProcessor(HDF5Container):
             self.unload_cells()
         return ({"rho": centers, "B": B_mean}, {"logbins": logbins})
 
+    def cos_vfluct_B(self):
+
+        mean_speed = self.save.get_node("/globals/mwa_speed").read()
+
+        def getter_cos_vfluct_B(dset):
+            vel_fluct = dset["vel"] - mean_speed
+            B_norm = np.sqrt(np.sum(dset["Br"] ** 2, axis=1))
+            v_norm = np.sqrt(np.sum(vel_fluct ** 2, axis=1))
+            # Compute the dot product in each cell
+            dot_prod = np.einsum("ij,ij->i", vel_fluct, dset["Br"])
+            return np.abs(dot_prod) / (v_norm * B_norm)
+
+        return self._vol_pdf(getter_cos_vfluct_B)
+
     def _mwa_sigma(self, axes=["x", "y", "z"]):
         mw_speed = self.save.get_node("/globals/mwa_speed").read()
 
@@ -817,9 +823,10 @@ class PostProcessor(HDF5Container):
             ),
             "cos_pdf": Rule(
                 self,
-                partial(self._vol_pdf, getter_abs_cos_vB, logbins=False),
-                "Global cos-PDF",
+                partial(self.cos_vfluct_B),
+                "Global cos fluctuation-PDF",
                 "/hist",
+                dependencies=["mwa_speed"],
                 unit=cst.none,
             ),
             "Brho": Rule(