What is the physical meaning of the AE index?



We would like to propose ceasing the derivation and distribution of the AE (Auroral electrojet) index because AE has no physically interpretable meaning and is therefore of no scientific value. Note that the term “AE indices” is different from the term “AE index;” the former includes the AU and AL indices, whereas the latter is just the AE index itself. (See below for the definition of AU and AL.)

Since the introduction of the AE indices by Davis and Sugiura [1966], scientists have relied on the indices to monitor the level of geomagnetic disturbance resulting from the auroral electrojets and hence, by proxy, to specify the state of the magnetosphere and the ionosphere. The AE index was defined by the separation between the upper and lower envelopes of the superposed H component plots from auroral-zone magnetic observatories. The upper and lower envelopes were defined as the AU and AL indices, respectively Thus, there is the relationship given by AE = AU - AL.