Comment on 'Geomagnetic Depth Sounding by Induction Arrow Representation:

themselves to the problem of describing the relationships be-tween various 'induction vectors ' as proposed by different in-duction workers. This in itself is an admirable exercise and certainly of great worth to the geomagnetic community, both for those studying induction effects and for those using ground-based magnetometers to d~termine ionospheric and magnetospheric processes. However, certain assumptions were made, but not stated, by the authors when comparing various 'arrows, ' and it is the purpose of this comment to state more explicitly some of those limiting assumptions and to give a more general relationship between time domain determined arrows and ffequency domain determined ones. Gregori and Lanzerotti state that the frequency domain real Schm.ucker arrow [Schmueker, 1970] is related to the time do-main Wiese arrow [Wiese, 1962] by (1) (their equation (11». The general Schmucker vector is complex and is derived from the inductive transfer functions given by Ziw) = z~w). Hn(w) + zo(w). Dn(w) + g ' (2) where Za(W) is the anomalous vertical magnetic field, Hn(w) is the normal (i.e., in the absence of a lateral variation in electri-cal conductivity) northward component of the horizontal magnetic field, Dn(w) is the normal eastward horizontal mag-netic field component, g'is the error of misfit, ~nd [ztAw), zo(w)] are the inductive transfer functions at frequency w. For single-station data, derivation of (ZH ' zo) given by (2) is not possible, and hence those transfer functions that relate the to-tal measured horizontal fields to the total measured vertical fields, as given b