diff --git a/hack/alfven_speed.py b/hack/alfven_speed.py
new file mode 100644
index 0000000..bb8003c
--- /dev/null
+++ b/hack/alfven_speed.py
@@ -0,0 +1,12 @@
+
+"""
+Created on Wed Jul 13 14:17:50 2022
+
+@author: aaboutal
+"""
+import numpy as np
+import astropy.units as u
+from astropy.constants.si import k_B, mu0
+
+def Alfven_sped(B: u.T, density: (u.kg / u.m**3)) -> u.m /u.s:
+    return np.abs(B)/ np.sqrt(mu0 * density)
\ No newline at end of file
diff --git a/hack/tmp8tdt783i b/hack/tmp8tdt783i
new file mode 100644
index 0000000..033759b
--- /dev/null
+++ b/hack/tmp8tdt783i
@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Created on Wed Jul 13 14:17:50 2022
+
+@author: aaboutal
+"""
+from astropy import units as u
+from astropy.constants.si import m_p, m_e
+B = 0.014*u.T
+n = 5e19*u.m**-3
+rho = n*(m_p+m_e)
+ion = 'p'
+Alfven_speed(B, n, ion=ion)
\ No newline at end of file