Tidal dynamo in the upper atmosphere. Validity and limit of the conventional theory.

The conventional two-dimensional approach to tidal dynamo in the ionosphere is based on several assumptions, one of which is the condition that no vertical electric current be present at the upper boundary of the ionsphere. An alternative condition is presented, which requires only the absence of a field-aligned current at the upper boundary. Under such a condition, an ionospheric electric field can be generated by tidal dynamo, but in a manner different from that in the conventional one. This process is described by considering the vertical current in a simple model ionosphere.