| Summary: | Electrostatic solitary waves with negative potential (ion holes) are analyzed
theoretically using a generalization of the treatment recently developed for
slow electron holes. It is shown that an often-cited criterion for their
existence is mistaken and they can in fact exist for a wide range of ion to
electron temperature ratios. Shifts of the hole velocity $v_h$ relative to the
ion distributions systematically decrease the permitted hole depths, which
become extremely small by $v_h/v_{ti}\sim 2$. Ion holes are usually unstably
accelerated by electron reflection forces which are calculated numerically and
analytically for the resulting asymmetric potential structure. The timescale of
this acceleration is proportional to the ion plasma period, and generally
longer than the ion bounce time in the potential well. Thus, ion holes behave
like approximately rigid entities and even when unstable can survive much
longer than the typical transit time of a satellite, so as to be observable.
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