Abstract
AbstractWith the aid of the Neutral Gas and Ion Mass Spectrometer measurements made onboard the Mars Atmosphere and Volatile Evolution, we examine the morphology of the nightside Martian ionosphere near the terminator at 150–250 km in terms of the extension into darkness for a selected set of ion species: O , NO+, HNO+, N /CO+, CO , and HCO+. Our analysis reveals several interesting characteristics, including the presence of dawn‐dusk and north‐south asymmetries and the variability among different species. A full interpretation of the Neutral Gas and Ion Mass Spectrometer observations relies on the combination of impact ionization by precipitating electrons and day‐to‐night plasma transport, as two important sources of plasma in the nightside Martian ionosphere near the terminator. The former partially contributes to the north‐south asymmetry, whereas the latter favorably explains not only the dawn‐dusk asymmetry but also NO+ and HCO+ as two exceptions which are more extended into darkness as compared to the other species on the dusk side. A comparison between the two plasma sources further indicates that the effect of day‐to‐night transport tends to be suppressed over the southern hemisphere. The above results highlight the impacts of crustal magnetic fields on the structural variability of the nightside Martian ionosphere near the terminator, manifest as the shielding of precipitating electrons and the suppression of day‐to‐night transport, both by the presence of strong magnetic anomalies clustering over the southern hemisphere of the planet.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call