Heavy ions of about mass 56 amu (probably iron ions) are observed at heights well above the F2 peak at concentrations of the order of 10² cm−3. Another ion (or ions) of intermediate mass (∼30 amu) and comparable concentration is also observed, but its identification is now obscure. The heavy ions are a common feature of the nighttime ionosphere, and it is suggested that they arise from meteor disintegration near 100 km and are then lifted by the dynamo electric field to greater heights. Readily resolvable structure in the variation of ion temperature with latitude is also observed, and it is postulated that these enhancements in Ti may be caused by the relative drift motions of ions with respect to the neutral atmosphere.
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Hanson et al. (1970) studied this question.