Abstract
We report for the first-time detection of ionospheric plasma depletion events (PDEs) in the primary ion species and thermal electrons at Mars. NGIMS/LPW measurements onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft reveal that PDEs are characterised by a sudden density decrease, at least by an order of magnitude, of all monitored ion species compared to their expected values at similar altitudes.
At the same time, the electron temperature typically considerably increases. The event occurrence appears to be related to the stronger crustal magnetic field regions in the southern hemisphere of the planet.
Additionally, the events are more frequent on the nightside than on the dayside. In this study, we focus on (1) the effect of magnetic fields (both induced and crustal) on the PDEs and (2) a possible formation mechanism and geometry of PDEs, demonstrating that they correspond to bubble-like structures in the ionosphere of Mars.
Finally, both local and remote electron density measurements performed by the MARSIS instrument onboard the Mars Express spacecraft are examined in order to check for possible conjugate measurements of these events and to discuss the event signatures in the radar sounding data.