Comment on “Edge enhancement of magnetic data using fractional-order-derivative filters” (Muzaffer Özgü Arısoy and Ünal Dikmen, Geophysics, 80, no. 1, J7–J17)

Arısoy and Dikmen (2015) discuss the application of fractional order derivatives to magnetic data. In particular, they fix the phase difference of the horizontal derivative with respect to the original data to be 90°, regardless of the order $n$ of the derivative that is used. This is equivalent to the order $n−1$ vertical derivative of the first horizontal derivative; i.e.,