Abstract
The theories concerning solitary waves and weak double layers in the auroral plasma are discussed. We make comparisons with Viking satellite observations and computer simulation experiment results of similar phenomena. The lack of velocity vs. amplitude relation in the Viking data is not consistent with the predictions of ion acoustic soliton theories and neither are the measured speeds of the structures. Numerical simulations show results, which are somewhat more consistent with Viking measurements but not with the ion acoustic soliton theory predictions. The nonlinear phase space ion hole instability offers another explanation for simulation results and space observations. Even there we still are quite uncertain, since the theory so far is only one-dimensional whereas the observations indicate that the solitary structures have a two- or three-dimensional shape with such scale sizes that the ions cannot be considered as one-dimensional.
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