Climatology of the Martian Northern Dayside Ionosphere Across Different Phases of Solar Cycles 24–25 Using MAVEN Spacecraft

Abstract The Martian ambient plasma environment varies with solar activity; however, the evolution of the topside ionosphere across different phases of solar cycles (SC) 24–25 remains a key research gap in planetary space research. This study uses NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission data (150–500 km) from Martian Years 32–37 (2015–2024) during solar quiet-time conditions to characterize the northern daytime topside ionosphere (e − , CO 2 + , O 2 + , NO + , OH + , O + , N + , and C + ) across SC 24–25 phases. The ionosphere shows a significant seasonal and latitudinal variation, with higher densities at low latitudes (0–30°N) than at mid-latitudes (31–60°N) throughout the SC. The topside ionosphere dependence on solar zenith angles (SZAs; 10–60°) is not significant below 350 km; however, ionosphere shows little variability above 400 km at higher SZA across SC phases. Additionally, the dayside ionosphere densities vary strongly with SC phases, with the highest densities during solar maximum than during weaker phases. Electron and molecular ion densities increased by factors of ∼1–5 and 1–13, respectively, while O + density enhances by ∼ 2–2.5 times, along with an upliftment of ∼40–50 km in peak height. The enhanced dayside plasma densities during the solar maximum are attributed to elevated EUV/SXR irradiance (∼1.4–6 times) compared to other phases.