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Is the Martian ionosphere symmetric in local time? Does the ionosphere change between aphelion, when there is no dust in the atmosphere, compared to perihelion, when the temperature rises and there is dust in the air even if no storm is blowing? We utilize data from the MAVEN Radio Occultation Science Experiment (Withers et al., 2020) - with unprecedented coverage in solar zenith angle - to answer these questions and isolate the effects that local time and season induce on the ionosphere at solar minimum. 219 out of the 1228 electron density profiles of the Martian ionosphere collected by MAVEN ROSE between July 2016 and December 2022 show, besides the ever-present dayside M2 layer, a distinct M1 layer right below. This allowed us to study the behavior of the M2 and M1 peak density and altitude as a function of solar zenith angle, and, also, for the first time, local time, and Martian season. We find that the M1 layer at low SZA can occur at altitudes lower than 100 km; that the peak altitudes and densities of both the M2 and M1 layers change more with season than at the dusk ionosphere; and that the M2 peak density decreases at a faster rate than the M1 with SZA. This study provides a baseline to accurately characterize the photoproduced Martian ionosphere at solar minimum.

We investigate the average configuration and structure of Saturn's magnetosphere in the nightside equatorial and high‐latitude regions. Electron data from the Cassini Plasma Spectrometer's Electron Spectrometer (CAPS‐ELS) is processed to produce a signal‐to‐noise ratio for the entire CAPS‐ELS time of operation at Saturn's magnetosphere. We investigate where the signal‐to‐noise ratio falls below 1, to identify regions in the magnetosphere where there is a significant depletion in the electron content. In the nightside equatorial region we use this to find that the most planetward reconnection x‐line location is at 20 – 25 RS downtail from the planet in the midnight to dawn sector. We also find an equatorial dawn‐dusk asymmetry at a radial distance of >20 RS which may indicate the presence of plasma depleted flux tubes returning to the dayside after reconnection in the tail. Furthermore, we find that the high‐latitude magnetosphere is predominantly in a state of constant plasma depletion and located on open field lines. We map the region of high‐latitude magnetosphere that is depleted of electrons to the polar cap to estimate the size and open flux content within the polar caps. The mean open flux content for the northern and southern polar caps are found to be 25±5 and 32±5 GWb, respectively. The average location of the open‐closed field boundary is found at invariant colatitudes of 12.7±0.6° and 14.5±0.6°. The northern boundary is modulated by planetary period oscillations more than the southern boundary.

We investigate the average configuration and structure of Saturn's magnetosphere in the nightside equatorial and high‐latitude regions. Electron data from the Cassini Plasma Spectrometer's Electron Spectrometer (CAPS‐ELS) is processed to produce a signal‐to‐noise ratio for the entire CAPS‐ELS time of operation at Saturn's magnetosphere. We investigate where the signal‐to‐noise ratio falls below 1, to identify regions in the magnetosphere where there is a significant depletion in the electron content. In the nightside equatorial region we use this to find that the most planetward reconnection x‐line location is at 20 – 25 RS downtail from the planet in the midnight to dawn sector. We also find an equatorial dawn‐dusk asymmetry at a radial distance of >20 RS which may indicate the presence of plasma depleted flux tubes returning to the dayside after reconnection in the tail. Furthermore, we find that the high‐latitude magnetosphere is predominantly in a state of constant plasma depletion and located on open field lines. We map the region of high‐latitude magnetosphere that is depleted of electrons to the polar cap to estimate the size and open flux content within the polar caps. The mean open flux content for the northern and southern polar caps are found to be 25±5 and 32±5 GWb, respectively. The average location of the open‐closed field boundary is found at invariant colatitudes of 12.7±0.6° and 14.5±0.6°. The northern boundary is modulated by planetary period oscillations more than the southern boundary.