Contour plots of the ratio of Ohm’s heating rate to ion-neutral collisions heating rate (in logarithmic scale) for periodically driven Alfvén waves in the upper solar chromosphere as function of the frequency f (vertical axis in logarithmic scale) and height above the photosphere (horizontal axis). We used the expression derived by Song & Vasyliūnas (2011, Eq. (A.5)). Left and right panels are the results obtained using the hard-sphere cross sections (HS) and the Vranjes & Krstic (2013) cross sections (VK), respectively. The red dotted line denotes the same heating rate for both mechanisms. We note that the VK results are only strictly valid for heights larger than 900 km.