The dayside structures of the ionospheres of Mars and Venus: Comparison and interpretation of results from a fast and flexible model with actual day-to-day observations

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The radio science experiments Mars Express Radio Science, Mars Global Surveyor Radio Science and Venus Express Radio science delivered a huge database of the ionospheric dayside electron density distribution of Mars and Venus, respectively. During the original proposal time frame, profile characteristics/environmental parameters were derived and a fast and flexible time-independent photochemical model of the ionospheric electron density (IonA-1) was developed for Mars (neutral atmosphere: Mars Climate Database) and Venus (neutral atmosphere: VenusGRAM). The comparison of MaRS and VeRa observed and modeled ionospheric main peak (M2/V2) parameters gave an excellent global agreement for Mars, but not for Venus (unrealistic VenusGRAM neutral atmosphere, Peter et al., 2014). However, a detailed agreement of the individual M2/V2 altitudes and widths is necessary for the modeling of additional small scale features. Matching observation and model main peak altitudes/widths indicate an approximate agreement between real and model neutral atmosphere during the time of observation. For the modeling of meteor layers below the secondary layer M1/V1, case studies for suitable MaRS profiles have been conducted in combination with a model for meteor layers (IonA/MSDM). MSDM considers the deposition of Mg and Fe into an atmosphere and computes the formation of metallic ions by photoionization/charge exchange. An additional 1D hydrostatic model of the neutral atmosphere at ionospheric altitudes (NIA) has been developed as a starting point for a more flexible neutral atmosphere at ionospheric heights with a small scale altitude grid to expand the applicability of IonA to a larger observational data set. IonA-1 has been upgraded into a time-dependent photo-chemical model with a complex reaction scheme (IonA-2) to yield results on ionospheric ion densities. The extended proposal shall couple NIA and IonA-2 to derive a more detailed understanding of the interaction between ionospheres and neutral atmospheres at ionospheric heights of Mars and Venus. The radio science lower neutral atmospheric observations are conducted almost concomitantly with the ionospheric observations and yield realistic first guess neutral densities for NIA. The computation of the coupled neutral atmosphere/ ionosphere with self-consistent neutral, ion and electron temperatures will (a) cover the transport regions of the ionospheric top-sides above the main peaks M2/V2, (b) yields a more realistic computation of the anomaly formation below M1/V1, (c) assess the contribution of secondary ionization within M1/V1/M2/V2, (d) explain the enigmatic bulge, a disproportionate accumulation of electrons in the topside and (e) provide possible states of the neutral atmosphere at ionospheric heights during the radio science observations. The last point will be very useful for the development of global circulation models, especially for Venus, where the data situation in this altitude range is poor.