The lower dayside ionosphere of Mars, corresponding to the M1 layer, is a weakly ionized and strongly collisional plasma region in which ion–neutral coupling is expected to strongly influence the evolution of electrostatic disturbances. However, direct waveform measurements in this altitude range remain limited. We investigate the nonlinear evolution of small-amplitude electrostatic ion-acoustic solitary structures in the Martian dayside M1 ionosphere and assess how plasma and neutral parameters control their propagation, attenuation, and observability under representative conditions constrained by observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Starting from a multi-fluid Boltzmann–Poisson model for O+2 ions, Boltzmann electrons, and a CO2-dominated neutral gas, we use the reductive perturbation method to derive a variable-coefficient Korteweg–de Vries equation with weak collisional attenuation. Here, the variable coefficients represent the dependence of the nonlinear, dispersive, stratification, and effective attenuation terms on the slowly varying M1 plasma–neutral background. The small-amplitude qualification refers to the asymptotic ordering used in the reductive-perturbation derivation, while the resulting solitary pulse remains intrinsically nonlinear. The results show that the intrinsic pulse shape is mainly controlled by the nonlinear and dispersive coefficients, whereas the pulse lifetime and possible detectability are controlled primarily by effective ion–neutral attenuation and neutral co-motion. Attenuation decreases with altitude; ion temperature makes the electrostatic pulses narrower and faster; neutral temperature has only a weak effect; and neutral density plays only a limited role in the co-moving case, while neutral co-motion provides the broadest range of behaviours, from strong attenuation to nearly adiabatic propagation. The co-moving M1 parameter sets satisfy the weak-attenuation criterion and permit a quantitatively controlled adiabatic solitary-pulse description, whereas the immobile-neutral limit violates this criterion for the representative pulse considered and is retained only as a qualitative upper bound on collisional attenuation. The electrostatic pulse has an electric-field amplitude of about 0.017 mV m−1, a frequency range of 6–7 kHz, and a duration of the order of 10−3 s. These predicted signatures provide observational targets for a future low-altitude Mars mission equipped with high-sensitivity, high-cadence electric-field waveform measurements and simultaneous plasma and neutral diagnostics.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)